Another electrical problem - Any Ideas?
Submitted: Friday, Jul 11, 2014 at 22:44
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Gnomey
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
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
AnswerID:
535942
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
FollowupID:
819933
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
FollowupID:
819943
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
FollowupID:
819949
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
AnswerID:
535981