Another electrical problem - Any Ideas?

Submitted: Friday, Jul 11, 2014 at 22:44
ThreadID: 108700 Views:1917 Replies:10 FollowUps:32
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My 2002 Troopy now sports a 140amp alternator - new within the past 12 months, two brand new MRV70 batteries fitted today, new battery terminals, clean old ones and all cables/terminals checked for voltage drop (zero) and all done by the local autosparky.

I also have Derek's ABR battery monitor to look at and it just keeps telling me something is just not quite right or at least that's how it looks to me.

Let's back up a touch. Last long trip was an early morning start in the dark, raining and cold. Plenty of load from headlights, heater fan and wipers and the fridge which runs off the house battery cycling on and off. Looking at the monitor occasionally, switching between the two batteries and noticed the voltage getting lower and lower - like down into the low 12's. By varying the load (switching things off and on) and the revs I could eventually get the alternator to kick in and charge at up to high 12's. Later in the trip I was coming back to camp from town - bugger all load and same pattern of dropping voltage and mucking around to get the alternator to kick in. Same thing happened at other times too.

We seem to have eliminated the possibilities of failing batteries and poor connections. This afternoon driving home everything seemed better. Not much load and charge across the cranking battery showing between 13 and 13.4. (Still a long way short of 14+ volts but better for sure.) Got home and turned on the headlights, went to high beam with the driving lights on too and there was the same pattern of voltage dropping down as far as 12.33 and seemingly no response from the alternator - mucking about with load and revs and then it would kick in - now at low 13's rather than high 12's. Kept at this for 15 minutes and sometimes the charge response was better and sometimes it wasn't - ie nothing like a predictable and consistent response to load.

Either Derek's monitor is bonkers or the alternator's not responding reliably to load or what I'm seeing is all actually normal and I just haven't noticed before because I didn't have an in-car voltmeter to see the fluctuations. Insert head scratching icon. Would appreciate input from the knowledgeable.

Cheers
Mark

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Reply By: pop2jocem - Saturday, Jul 12, 2014 at 00:25

Saturday, Jul 12, 2014 at 00:25
Mark,
The first thing I would do is put a multi meter across the batteries to make sure that what the volt meter is telling me is what the batteries are seeing.

Cheers
Pop
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Follow Up By: Member - John and Val - Saturday, Jul 12, 2014 at 08:49

Saturday, Jul 12, 2014 at 08:49
Mark,

I agree with Pop, get a second opinion from a multimeter connected directly across the main battery. (In my experience, Derek's gear is good, but nothing's perfect.) With the engine at fast idle I'd expect over 14V across the main battery, maybe dropping a little, certainly less than half a volt, under maximum load. (You are actually measuring alternator output rather than battery voltage under these conditions, and your big alternator should handle that load easily.) If the alternator can't deliver an almost constant voltage regardless of load then I'd look for a problem around the alternator and its sensing circuitry.

Cheers

John


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Follow Up By: Member Kerry W (WA) - Saturday, Jul 12, 2014 at 09:57

Saturday, Jul 12, 2014 at 09:57
Sounds like faulty voltage regulator.
hope this helps
Kerry W (Qld)
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Reply By: John and Regina M - Saturday, Jul 12, 2014 at 08:02

Saturday, Jul 12, 2014 at 08:02
So what does the local autoelectrician say?
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Reply By: Nomadic Navara - Saturday, Jul 12, 2014 at 08:47

Saturday, Jul 12, 2014 at 08:47
You say that the alternator kicks in when you reduce the load. To me that indicates fan belt tension. Check that it is not too loose. The other ting it could be is that the new alternator is not up to scratch (premature failure.) Do you still have the old one to fall back on? Put it back to check your system.
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Reply By: Athol W1 - Saturday, Jul 12, 2014 at 09:07

Saturday, Jul 12, 2014 at 09:07
MArk
It sounds very much like slipping belts to me, did you fit new belts at the same time as fitting the new alternator. The life of the twin belts fitted to these engines is only 100,000km and any re-tensioning of the belts beyond that will not prevent slipping of the belts, and it is the alternator pulley that will slip, and not always make any noise when doing so. It is also possible that the belts have 'bottomed out' in the pulleys and therefore not have the ability to transfer the required load to the alternator, bottomed out belts often do not make any noise, just don't work.

It takes two and a quarter horsepower to drive your alternator when it is delivering its rated power output.

Hope this helps.
Athol
Retired motor mechanic.
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Follow Up By: Ross M - Saturday, Jul 12, 2014 at 09:24

Saturday, Jul 12, 2014 at 09:24
I bet the actual belt energy transfer is closer to 5 horsepower though.
A 2 1/4 HP engine wouldn't have a hope in hell of driving a 140 amp alt.
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Follow Up By: Gnomey - Saturday, Jul 12, 2014 at 09:35

Saturday, Jul 12, 2014 at 09:35
Sorry mate. Missed responding in my reply. The belts would be <50k old and fitted before the change in alternator so I am doubtful that they are worn out but I'll check and have this checked by the sparky.

Consistent with slippage is that the variation doesn't seem to happen at idle but typically at road rpm of around 2200 and I have produced it with rpm of around 1500 when sitting still. On the other hand it also comes and goes at those revs without any load changes or any other discernible pattern. To me that unpredictably suggests electrical rather than mechanical issues.

Cheers
Mark
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Follow Up By: Athol W1 - Saturday, Jul 12, 2014 at 10:02

Saturday, Jul 12, 2014 at 10:02
Ross M
I agree that the total load on the belts would/could be around the 5HP I based my figure on 1 HP being 746 watts, so the electrical load only, for total load you have to include the water pump, cooling fan, vacuum pump loads and mechanical losses.

Mark
Even at 50,000km on the belts if they have been slipping I would replace them, any glazing of the belts will cause slippage.

The symptoms that you describe are consistent with loose/slipping belts as the maximum load from an alternator occur at around the 1500/1800 RPM range, and the slippage of belts can be very not uniform in it nature.

Regards
Athol
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Follow Up By: Ross M - Saturday, Jul 12, 2014 at 17:49

Saturday, Jul 12, 2014 at 17:49
Athol
Although 746w is apparently equivalent to 1 hp, it doesn't follow that the alt will require that and it is applicable in the alternator situation. Without the ancillaries like a water pump and fan it will be up near 5 hp to drive 140amps out of an alternator. Hence the two belts to transfer the energy.

A 2.2hp engine running at optimum will only deliver approx 50 amps and many 5hp engines running similarly will barely provide 140amps.
The alternator has losses and absorbs power and the energy conversion isn't anywhere near 746W of output equaling a HP under those conditions.
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Reply By: Gnomey - Saturday, Jul 12, 2014 at 09:26

Saturday, Jul 12, 2014 at 09:26
Morning all and many thanks for your suggestions. I will recheck the fan belt but after the new alternator was fitted I adjusted the tension twice. Also there's no sound of slippage and the variable voltage happens with the engine running at constant revs of 1500rpm or more but still I will check and adjust tension.

I haven't compared my multimeter directly with the battery monitor during one of the weird events I've described, but I have compared them several times and the readings have the same differential of about .05 of a volt between the two. But again, sound suggestion I will take up

I have never had 14v or more out of the alternator and John's comments nailed it for me when he said that the output should not vary by more than 0.5v when under load.

The autosparky sold me the alternator so I would expect him to eliminate all else before confronting the possibility of the alternator being defective. Come Monday though, I will be putting it to him to face that or demonstrate another cause.

Cheers
Mark
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Reply By: olcoolone - Saturday, Jul 12, 2014 at 10:06

Saturday, Jul 12, 2014 at 10:06
Sounds like the diodes are not getting excited properly..... meaning there could be something wrong with the internal reg in the alternator...... or a bad connection.

With the vehicle running take a reading and then place it under load (headlights hi beam, rear window demister on and ac/heater fan on full) and recheck the voltage..... if it's OK wriggle and yank all the looms and wires in the engine bay and see if you get a differant reading.

If you multi meter has a maximum/minimum hold button use that as the meter will record faster then you can see.
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Follow Up By: Ross M - Saturday, Jul 12, 2014 at 12:42

Saturday, Jul 12, 2014 at 12:42
Diodes don't get excited do they?? Just one way valves.
Although in an alternator there are diodes, termed exciter diodes, which "excite" the rotor winding with energy.

A diode rarely repairs itself and therefore if faulty will not supply to the regulator for regulation of power output.
The regulator in and alternator is a current control device (decided by a voltage level at the alt output terminal), to control the current to the rotor winding, thereby controlling the alternators energy output to be able to achieve the required voltage output.

If it is varying them belt or dirty connection.
If the belt is slipping then there the excitement level will below.
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Follow Up By: olcoolone - Saturday, Jul 12, 2014 at 18:15

Saturday, Jul 12, 2014 at 18:15
So what are the 3 diodes.... you know one for each phase that supplies field current to the regulator?

The 3 that require a slight load like the alternator light to get them working commonly called exciting the alternator!

Ross they (the diodes) do not excite the rotor winding, they them selves (the exciter or field diodes) need to be excited by a outside source like a dash light or resistor that in turn opens them up allowing the field current to flow to the regulator.

If they were not there instead of being an alternator it would be a motor.

And if you could understand English properly....

""""""Sounds like the diodes are not getting excited properly -

meaning there could be something wrong with the internal reg in the alternator...... or a bad connection.""""""

Seen low temp solder used in the diode packs that had melted causing a intermittent poor connection.
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Follow Up By: Ross M - Sunday, Jul 13, 2014 at 10:21

Sunday, Jul 13, 2014 at 10:21
The exciter diodes simply pass electricity.
They DO NOT pass the indicator globe current to initiate the rotor excitation.
The rotor requires excitation to begin operation unless there is some residual magnetism in the rotor mass.
The indicator runs it's current into the regulator AFTER the exciter diodes.
The exciter diodes are to supply rectified current from the stator AFTER the rotor has been excited by the globe trickle into the regulator.
In a Bosch alternator there is no connection between the stator outs and the exciter diodes otherwise the globe current would be lost through the other diodes to neg and NON would get to the regulator for initiation purposes.

So the exciter diodes are then continually supplying rectified current to the regulator and rotor for continued excitation and current control.

Until it excites and begins to charge, NO current flows through the exciter diodes at all because there is NO current being produced in the stator.
The only current which goes through the exciter diodes comes from the stator windings.

You appear to know what is in there, just not how it works.

I learned that very well during my 2nd year of apprenticeship and it hasn't changed.
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Follow Up By: Allan B (Member, SunCoast) - Sunday, Jul 13, 2014 at 13:43

Sunday, Jul 13, 2014 at 13:43
And here's a picture children...............

Cheers
Allan

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Follow Up By: olcoolone - Sunday, Jul 13, 2014 at 15:36

Sunday, Jul 13, 2014 at 15:36
Ross I am not even going to argue with you.....

So this youtube video like all the rest are wrong?????

https://www.youtube.com/watch?v=QPl7CTb685I

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Follow Up By: Ross M - Sunday, Jul 13, 2014 at 15:59

Sunday, Jul 13, 2014 at 15:59
Yes. No need for argument because as Allan has shown, the lamp doesn't pass it's excitation current through the exciter diodes. So the diodes aren't in questions at all.

Thanks Alan
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Follow Up By: Allan B (Member, SunCoast) - Sunday, Jul 13, 2014 at 17:14

Sunday, Jul 13, 2014 at 17:14
Let me have a go Ross.

Olcoolone, No wonder that you are confused if you gain your information from that referenced video! That guy may have some understanding but he sure cannot communicate it, and I quote him.......... "The stator gets its power from the battery post on the back of the alternator"!!!! That is totally wrong. The stator doesn't get its power from anywhere, it produces power and supplies it TO the battery post on the back of the alternator.

Anyway, this post has been discussing the alternator 3-wire type where the initial excitation is gained from an external 12v source derived from the ignition circuit via the alternator indicator lamp. Your video guy is talking about "self exciting" alternators where the initial excitation is gained from the residual magnetism of the rotor field pole piece. He even uses the term "residual magnetism".

So your video is not "wrong", merely not the right alternator video for this discussion. Why you argue with people with appropriate training is beyond me.

Cheers
Allan

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Follow Up By: olcoolone - Sunday, Jul 13, 2014 at 19:01

Sunday, Jul 13, 2014 at 19:01
I know I know, good to see some are on the ball and read my posts.....

Yes Ross I know the rotor needs a bit of a kick start to get working.

"Why you argue with people with appropriate training is beyond me."

What else is there to do, I would of expected a few others to join in the war.....
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Follow Up By: Allan B (Member, SunCoast) - Sunday, Jul 13, 2014 at 19:12

Sunday, Jul 13, 2014 at 19:12
LOL Richard, LOL
Cheers
Allan

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Reply By: Gnomey - Saturday, Jul 12, 2014 at 10:29

Saturday, Jul 12, 2014 at 10:29
You folks are the winning ticket.

I just went out and tightened the belts much tighter than before. Picked up on comments about the amount of hp required to drive this non standard alternator and added about 30% to the tension I would otherwise use. Bingo. Over 14v output, peaking momentarily at 14.56v when the headlights and driving lights are switched off then sitting at 14v+.

Now for the new belts to replace the ones that have been slipping all this time and a word in the ear of the autosparky who might reasonably be expected to have saved me the grief. :)

Cheers and thanks again guys. It's appreciated.

Mark
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Follow Up By: The Bantam - Saturday, Jul 12, 2014 at 11:21

Saturday, Jul 12, 2014 at 11:21
If you are accustomed to working on pasenger cars with relativly small alternators..like the old 55 amp bosch.

You may have to alter you expectations of belt tension.

There is a good reason why many of these 4wds and light trucks run twin belts on the alternator and have lead screw tension adjustments.

because the belts need to be tightaer than you could manage with a broom stick stuffed betwen the alternator and the engine block.

cheers
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Follow Up By: Zippo - Saturday, Jul 12, 2014 at 11:38

Saturday, Jul 12, 2014 at 11:38
Be aware that if belt slip was the problem, the working faces of the alternator pulley may now be so polished that the problem may return sooner than you'd like and trying to fend it off by progressively increasing the belt tension may lead to bearing failure.
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Follow Up By: Bob Y. - Qld - Saturday, Jul 12, 2014 at 11:39

Saturday, Jul 12, 2014 at 11:39
Like the reference to the broomstick, Bantam. Always preferred a CAT bar myself :-)

Have often used a CRC product "Belt Grip" on slipping/glazed belts. Works well in the interim, except it seems to go everywhere, as well as on the belts and pulleys.

Also prefer Bosch or other after market belts, for Tojo alternators. To me they seem to last better than the genuine article.

Bob

Seen it all, Done it all.
Can't remember most of it.

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Follow Up By: Gnomey - Saturday, Jul 12, 2014 at 11:42

Saturday, Jul 12, 2014 at 11:42
True but in my own defence I got specific advice about belt tension from a mechanic whose advice is worth taking. I set the belts, all of them, as he suggested with rotation through about 90deg being "just" doable with the fingies.

It's a longer story too. I'm mindful of belt tension after earlier disasters when the crank pulley delaminated and the keyway then got turned out after pulley replacement and the resulting jackhammer vibration buggered the engine. Not my work or fault btw. Not caused by belt tension but you can see it's an area that got my attention - enough tension but not too much.

"with a broom stick stuffed betwen the alternator and the engine block." Or even a chrome vanadium tyre lever, mate. :)

Bigger picture. I take it as another commentary on mods and "unforeseen" consequences. At out peril do we assume the unnecessary conservatism or even incompetence of the original design team.

Cheers
Mark
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Follow Up By: pop2jocem - Saturday, Jul 12, 2014 at 12:14

Saturday, Jul 12, 2014 at 12:14
Mark,
It sounds like you are pretty tuned in regarding belt tension and the consequences thereof.
That's one big mother of an alternator you have there and I'm sure you have good reasons for fitting it. I can't remember what size your model had as standard but a bit less than that if memory serves me right. I guess when Mr Toyota designed the original system as a whole taking into account what current draw could reasonably be expected to be supported by the original alternator he would have allowed for that plus whatever other bits and bobs are driven off those belts,i.e. the fan and water pump.
Just a thought mate but maybe the belts are fighting a bit out of their weight division. Tightening them to prevent slippage during an event where full or close to full output is demanded from the alternator is of course putting extra strain on all the bearings involved, mainly the water pump as I would hope the alternator manufacturers would have fitted bearings of appropriate size.

Cheers
Pop
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Follow Up By: Member - John and Val - Saturday, Jul 12, 2014 at 13:03

Saturday, Jul 12, 2014 at 13:03
Good find Mark, and a good example of why this forum is so valuable. Those with a mechanical background thought in terms of belts and pulleys and the power that was being mechanically transferred. With an electrical history some of us thought in electrical terms. Put it all together and there's a result.

Cheers

John
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Follow Up By: Gnomey - Saturday, Jul 12, 2014 at 13:46

Saturday, Jul 12, 2014 at 13:46
Pop. I'm hearing you mate. Truth is when the old alternator went south I was offered two alternators, one about 120 or 130amp and this 140amp version. At the time I didn't think of and wasn't made aware of, any mechanical consequences and the price difference wasn't much.

So what now? I doubt the transaction is reversible at this point. I will discuss it with the sparky but assuming it isn't swappable it's either take a $700 hit or reface the pulleys to take off the shine Zippo mentioned (I'm thinking a diamond hone or two), fit new belts and adjust the tension until the output is correct, monitor and hope for the best on the other driven devices.

Only other point I can think of is that maybe the load on the alternator will vary my way given that the higher output should get the charging job done a bit sooner and that I don't drain batteries needlessly. eg I've bought a folding solar panel to help when I'm camped in one spot for a few days.

Cheers
Mark
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Follow Up By: The Bantam - Saturday, Jul 12, 2014 at 16:12

Saturday, Jul 12, 2014 at 16:12
If you have a service manual...and you should...it may have a properly expressed way of specifying belt tension.

The service manual for my hilux does...and its a lot more than I expected.

Again these alternators with dual pullies have bigger and beefier bearings than the old 55 amp units found in some passenger cars.

lets not complicate the issue and look for problems that just aren't there.

A new set of belts and tensioned to spec and 90% liklihood of it being just fine.

Persoanlly I would not entertain replacing an alternator and not the belts unless it was a crisis repair.

cheers
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Follow Up By: Athol W1 - Saturday, Jul 12, 2014 at 17:14

Saturday, Jul 12, 2014 at 17:14
Mark
Polished pulleys are not normally a problem, but can easily be 'roughed up' with the use of some emery tape.

Worn pulleys allowing the belts to bottom out are a problem, and likewise glazed belts are a problem and both of these issues require replacement to rectify.

With new belts fitted ensure that you can not deflect the belts more than about 8mm midway on their longest run with good firm pressure by hand (about 10mm for used belts), this will ensure that the belts are tight enough without being tuned to the key of G. These vehicles are designed for this type of loadings on the relative bearings.

The 'twist 90 degrees' applies to timing belts, I have never heard of it being applied to V belts.

Regards
Athol
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Follow Up By: Ross M - Saturday, Jul 12, 2014 at 17:58

Saturday, Jul 12, 2014 at 17:58
Gnomey
If changing pulleys you can always use a larger pulley to more easily cater for the load and it should still charge a little amount when at idle speed.
An alternator usually only has to run around 2000rpm for maximum output to occur, any rpm after that is not used. So some mod there may be ok for it to work without excessive belt tension and bearing failure and still work adequately for your system.
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Follow Up By: The Bantam - Saturday, Jul 12, 2014 at 18:27

Saturday, Jul 12, 2014 at 18:27
sorry but generalise rules about deflection of belts, just wont cut it with many of these higher powered alternators.

If you are to work from the specifications you need to know how much force and how much deflection you need to be seeing.

with belts heavier and shorter than the old single belts on the 55 amp alternator...you may have to apply quite a bit of force to get any deflection at all.

get the manual and look at the specs in there.


with respect..why are we talking about fiddleing with pully sizes...the replacement alternator in quetion is not a great deal larger than factory and we have not installed a high RPM high performance engine.

The factory standard pully sizes are chosen for very good reasons.

as far as RPM above 2000 rpm not being used...um sorry I have a graph (actual measured of my alternator) in front of me, of the alterenator in my vehicle and it shows maximum output occuring at arround 6000 RPM shaft speed..on my vehicle I estimate the shaft ration to be about 2:1
So my alternator does not achieve maximum output till arround 3000 RPM engine crank speed which is what the vehicle cruises at 100Kmh in fifth gear.

At 2000 rpm crank speed about 4000 rpm shaft speed my alternator is only producing 80% of its rated output.

lets stop talking about fixing problems that almost don't exist.

as long as the pullies are not obviosly worn.....new belts and the correct as specified belt tensions should be all that is required.

cheers
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Follow Up By: Gnomey - Saturday, Jul 12, 2014 at 21:05

Saturday, Jul 12, 2014 at 21:05
Athol and others on a similar tack. I will have a civilised chat with the autosparky. It's in both our interests to come up with a cheap and sensible plan.

I don't think the alternator pulleys are shot, rather they probably need a rub to brush the sheen off - emery paper, coarse wet 'n dry a medium or rough diamond hone should all do the job.

I just want to be clear the 140amp beastie and its extra 1hp demand at full capacity are sustainable using the standard belts at the specified tension. If so, I'm not fussed. Lesson learned as it were.

Sure the 1HZ hasn't got that many surplus hp's to be spending like there's no tomorrow but it won't be running at full output a lot of the time unless there's something I'm not understanding properly.

I reckon you guys have it sussed.

Cheers
Mark
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Reply By: howie - Saturday, Jul 12, 2014 at 11:51

Saturday, Jul 12, 2014 at 11:51
about 2 months ago i had a alternator go faulty, no problem, mechanic bolted on a new one.
the first replacement was overcharging, which was easily diagnosed and alt #2 was put in.
still had battery charging problems, which seemed to be another faulty alt.
alt #3 goes in, same problem, charges when the motor was first started, then after about 8-15 minutes it stopped charging.
at this point, after checking every other possibility and 3 alt's later, we thought maybe its a wiring problem (suspecting a sense wire and, surely not, the original alt could have been ok?).
turns out to be a batch of faulty alt's (lucky me) with their internal (chinese) regulators.
the only way it was proved was by a auto sparky doing some proper bench testing.
it was probably one of the more annoying things that has gone wrong with the patrol and not easily diagnosed without 20/20 hindsight.
good luck.

AnswerID: 535950

Follow Up By: pop2jocem - Saturday, Jul 12, 2014 at 12:26

Saturday, Jul 12, 2014 at 12:26
A mate of mine had an alternator die on a Commodore, about 2009 model I think. So to save himself a bit of labour cost he removed it himself and took it an auto sparky. Now this was not the easiest job for anyone and this guy is about 6'4", around 120 kg with hands and arms to match.
You can imagine his expression when the sparky told him he couldn't test it properly without it being fitted to the car as the output was controlled by one of the many computers that infest our newer model cars and not by an inbuilt regulator.
So he had to take it home and refit the horrible thing and then take it to the sparky. To say he was not a happy camper would be putting it mildly.

Cheers
Pop
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Follow Up By: howie - Saturday, Jul 12, 2014 at 14:54

Saturday, Jul 12, 2014 at 14:54
sounds about right.
when i say bench test, i think they left it on my truck and replaced all the leads, including the 'sense' wires, connected to their testing equipment.
i used to think that maybe auto sparkys have some sort of means to attach an alt to a belt on a bench motor, but with all the different fittings etc, this would be difficult.
BTW i have loads of patrol wiring diagrams to sell LOL
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Follow Up By: The Bantam - Saturday, Jul 12, 2014 at 16:18

Saturday, Jul 12, 2014 at 16:18
An auto sparkey I know has a rig that fits in his lathe....he has a spigot that chucks up in the chuck, to this he fits the appropraite socket that mates with the pully shaft nut.

The adjustable jig clamps into the ways of the lathe...the traveler comes up behnd the jig to hold it all firm.

he then has the fll range of speeds in the lathe to play with.

back in the day he had a board screwed to the wall behind the lather with a selection or regulators and wires for testing a variety of laternators.

cheers
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Reply By: MUZBRY- Life member(Vic) - Saturday, Jul 12, 2014 at 14:37

Saturday, Jul 12, 2014 at 14:37
Gday
Does the new alternator have a metric pulley or an imperial pulley as the V is cut at a different angle , making the belts slip through lack of contact in the V.....
Muzbry
Great place to be Mt Blue Rag 27/12/2012

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Follow Up By: Gnomey - Saturday, Jul 12, 2014 at 14:45

Saturday, Jul 12, 2014 at 14:45
Thanks Muzbry. I don't know but I'll ask and find out. We might as well eliminate all the potential issues rather than letting them rattle out along the track.

Cheers
Mark
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Follow Up By: olcoolone - Saturday, Jul 12, 2014 at 18:30

Reply By: pop2jocem - Saturday, Jul 12, 2014 at 20:14

Saturday, Jul 12, 2014 at 20:14
Mark,
As far as I can tell the standard alternator for your model year was a 110 amp max output. The 140 amp unit you have is, on paper, capable of about 33% greater output.
Now keeping in mind that if it has the correct diameter and groove angle pulley and it is not being called on to produce the output it is capable of, having the belts a little tighter should not cause any dramas. If for some reason the batteries are very low the alternator will attempt to produce whatever it is capable of. I would assume you haven't driven a great distance with this unit fitted so a roughening up of the pulleys on the crank and the alternator may see you right.
Well worth checking out the belt is not bottoming out and that the grooves are the correct angle as others have suggested.
Worth a shot. Personally I wouldn't get over enthusiastic with over tensioning the belts.

Cheers
Pop
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