Unusual and rather funny car audio problem - help required

Submitted: Saturday, Oct 31, 2015 at 17:55
ThreadID: 130751 Views:2484 Replies:8 FollowUps:10
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Howdy All

I purchased a 1996 Mitsubishi Delica as a project to turn into a campervan. Everything has been moving along nicely until a couple weeks ago when I had a double din head unit Radio / CD, with GPS, Bluetooth, DVD, Reverse camera and Ipod connection I bought off ebay installed. I had a mobile auto electrician come and do some other work on the van and while he was here I asked if he could help with installing the new unit as I'm not that good with electrics.

We got the old unit out and the new one in and it was pretty much plug and play apart from one lot of wires which we had to cut and shut as the plugs didn't marry up. Turn the unit on - all good, radio works, cd works, dvd works, gps works, synced my mobile phone in under 30 seconds - unbelievable for a non techo like me - didn't fit the reverse camera as I will do that later so I'm happy. Pay the auto eleccy and he goes home.

An hour later I thought I would go for a drive and test the gps out - start the van and straight away the volume goes to max volume - play with the buttons and can't turn the volume down. Turn off van take key out, put key in and turn on accessories - everything fine - volume button works, all good. Start the car and volume goes to max in 3 seconds. Turned it off and sat there playing when I realised that each time I touch the brake pedal the stereo increases one number with each tap of the brakes or if I hold my foot on the pedal it just steadily increases until it reaches max volume - I hope you are laughing by now coz it's soo funny !

Rang auto sparky and he's at a bit of a loss as the only wires he cut were on the original stereo wiring loom in the centre of the dash. He lives 80 k's away from me and I'm just trying to get some advice and suggestions before I head to his place to hopefully and easily rectify the problem.

Today I pulled the brake light fuse and there is no problem with the volume on the unit.

Any advice is much appreciated ( even suggestions about wearing ear muffs or not using the brakes is fine as I think this is funny )

All the best


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Reply By: The Bantam - Saturday, Oct 31, 2015 at 18:20

Saturday, Oct 31, 2015 at 18:20
#1 in times past car radios had one power supply wire ...... these days most have two, one to be connected to a permanent source of supply, the main feed , a second to be connected to a switched accessory feed.

If you drop the whole power supply to many of these radios they go into a set up routine and need certain settings reset ..... like they wont remember the volume they where last set to.

As for the brake light thing ........ hell man got me buggered .......

these days I would not cut a loom in a dash ...... I would either plug into the socket provided with individual pins or buy a tail for that brand of vehicle and wire to that.

For a lot of vehicles and stereos, you can buy an adaptor set ...... say, toyota to pioneer.

AnswerID: 592192

Follow Up By: The Bantam - Saturday, Oct 31, 2015 at 19:39

Saturday, Oct 31, 2015 at 19:39
In addition many of the newer stereo uints draw quite a bit of power ....... back in 96, ya standard factory radio/cassette or if it was a luxury CD unit output arround 6 Watts RMS per channel, two channels , even the most basic units these days output around 20 watts RMS per channel, 4 channels pluss the additional current drawn by the computer smarts .....so ya stereo has gone from drawing abot 2 to 3 amps to arround 10 + amps..... at full noise.....its probably wise to not depend on the factory 12V supply or 0V chassis connection in the dash and run a heavy supply both 12V and 0 volts direct to the battery.

FollowupID: 860314

Follow Up By: Phil 23 - Tuesday, Nov 03, 2015 at 09:25

Tuesday, Nov 03, 2015 at 09:25
I've used a couple of the ISO conversion cable sets, they only cover the basic connections & sometimes have mismatches.
Have done Ford, Mitsubishi & Toyota to Pioneer.

In all cases the ISO cables usually have 2 plugs, one with 8 pins for the 4 speakers,
the other with eight pins, but often only the last 5 connected, 1,2 & 3 can be optional.

1.-Speed sensitive volume control, (haven't seen that one).
2.-Cell phone mute (not present in the sets I've used).
3.-Revers light signal ( not seen on the Aeropro sets I've used either).
4.-Ignition/Accessory 12V
5.-12V output (for accessories like aerials & amps).
6.-Dash light illumination
7.-Battery/Permanent 12V

So in the example of the installation of a Pioneer DVD head in a 2003 Pajero I found.

I had to patch thru the reverse light signal, not present in the vehicles plug, to get the reverse camera to operate.

Similar thing with the hand brake signal to inhibit video while driving, ran a bit short on wire on that one, think it's touching ground somewhere.

The dash light signal also wasn't patched thru on the Pioneer to ISO side, so had to add a pin from the original harness for that.

Found the dash light one to be a waste of time as it dimmed the display when I drove with park lights during the day so disabled that & used the units time based dimming option.

Toyota was same head similar situation, but found that the radio had weak reception on AM stations, barely receiving local stations.

Turned out some more patching was required to feed power to the Toyota's amplified aerial, which only required power for AM reception and not FM.

Moral of the story is the ISO harnesses only patch thru the basic connections.

Hope that info is useful.

FollowupID: 860438

Follow Up By: The Bantam - Tuesday, Nov 03, 2015 at 10:49

Tuesday, Nov 03, 2015 at 10:49
While the direct and model specific adaptor harnesses exist, some of the auto stores do not stock them or even have them available for special order ....... instead they stock bare lead tails and ISO adaptors......

The plain tails simply allow you to plug directly into the existing harness and do what you like on the tail provided ...... thus no excuse for butchering the factory loom.

You take the tail that came with the stereo and splice it to the tail you plug in to the factory loom that exists in the vehicle. using or ignoring what ever wires are appropriate.

While they may not solve all problems, the model specific direct adaptors you will probably find give less problems than going too amd from using iso adaptors. ...and in some cases they are a straight plug and play option.

On the specific matter of ISO adaptors ........ I would not consider them unless I was connecting to a device or a vehicle that already had ISO compliant connectors in place. ... which is pretty much no, Japanese, Asian, Australian or American made vehicle.

There is pretty much no excuse for butchering a factory vehicle harness.

FollowupID: 860442

Follow Up By: Phil 23 - Wednesday, Nov 04, 2015 at 06:44

Wednesday, Nov 04, 2015 at 06:44
Plain tails from the factory harness would be ideal if easily sourced, but in the case of the Kluger & Pajero they weren't readily available.

In the case of the Pajero, the factory connector still excluded both reverse & handbrake signals.
They had to be picked up elsewhere.

And agree, I'd never butcher a factory connector & remove it. The ISO's have always got the job done with only 1 or 2 additional wires.

FollowupID: 860485

Reply By: Ross M - Saturday, Oct 31, 2015 at 18:40

Saturday, Oct 31, 2015 at 18:40
Modern units DO NOT increase the volume via a potentiometer/volume control.
They use stepped volume increase by having a rotary or button pulse control which makes pulses to increase the volume.
It seems the vehicle systems have some sort of pulse in the wiring, ie Brake pulse causing lower and then higher voltage in the supply line.
Try adding a large Electrolytic capacitor just before the unit so there is a more constant voltage applied to the unit and hence reducing pulse effects.
Also a wiring choke, usually wiring traveling through a ferrite core, which absorbs and reduces pulses in the line.

The Capacitor should have it's positive to the power wire and the negative to vehicle earth/negative.
They go BANG the other way around, so be careful with that connection.

One or both may rectify the problem. Especially if the unit doesn't already have a ferrite choke in the power input line.
AnswerID: 592194

Reply By: Notso - Saturday, Oct 31, 2015 at 20:41

Saturday, Oct 31, 2015 at 20:41
A bad earth can do funny things! The Stop lights not earthed well? Ah well you never know!
AnswerID: 592196

Reply By: Member - Outback Gazz - Sunday, Nov 01, 2015 at 08:55

Sunday, Nov 01, 2015 at 08:55
Thanks Bantam and Notso - will be noting this when seeing auto sparky next.

And a special thanks to Ross M - as we have had our indifferences on this great site in the past so I appreciate your time and effort very much - Thankyou !

As this is way beyond me I will definitely be handing this info over to the man with the skills - he hasn't done a lot of car audio systems as he's fairly new in the game but I absolutely love his work with lights and switches etc .

Any other suggestions from car audio experts out there ???

Thanks guys

All the best


AnswerID: 592205

Reply By: Member - Outback Gazz - Tuesday, Nov 03, 2015 at 07:47

Tuesday, Nov 03, 2015 at 07:47
Howdy All

Any more suggestions before I head down to the auto sparky's place next week ??

Any little tip could help in some way !



AnswerID: 592295

Reply By: Phil 23 - Tuesday, Nov 03, 2015 at 08:40

Tuesday, Nov 03, 2015 at 08:40
The First thing I see as a key here is the brake light.

The only reason a head unit is connected to a brake circuit is to disable video playback while the vehicle is in motion.

But that wire is usually connected to the hand brake not the foot brake.
If the hand brakes not on, you can't watch videos. Simple, (Opps).

Second thing is does the unit have wiring for external volume control?
A wire for up & another for down, probably intended for connection to steering wheel controls.

So with all that my guess is there's been a wiring miss match, with a volume up line taken to the brake pedal.

Do you have a make & model, and maybe a link to a manual with a wiring diagram?

AnswerID: 592299

Follow Up By: Phil 23 - Tuesday, Nov 03, 2015 at 08:43

Tuesday, Nov 03, 2015 at 08:43
Also, is it one of these cars that you can't start without your foot on the brake?
That would also fit the situation you describe.
FollowupID: 860430

Follow Up By: Member - Outback Gazz - Tuesday, Nov 03, 2015 at 09:00

Tuesday, Nov 03, 2015 at 09:00
Thanks Phil

That has given me some more ideas to take to the auto electrician. Don't need foot on brake to start !

Appreciate your time and reply


FollowupID: 860435

Reply By: TomH - Tuesday, Nov 03, 2015 at 08:47

Tuesday, Nov 03, 2015 at 08:47
I would take it to a car radio installer rather than a sparky who is clever "fitting switches".

Places like Autobarn and Super cheap do them all the time and would have a far better idea then any house sparky.

I have a clever sparky but wouldnt let him loose in a modern car.
AnswerID: 592301

Follow Up By: Member - Outback Gazz - Tuesday, Nov 03, 2015 at 09:03

Tuesday, Nov 03, 2015 at 09:03
Thanks Tom

He's a qualified auto electrician who has been out on his own for 7 years but has not done a lot of stereo installs.


FollowupID: 860436

Follow Up By: The Bantam - Tuesday, Nov 03, 2015 at 10:56

Tuesday, Nov 03, 2015 at 10:56
Yeh great that you have confidence in this bloke ...... but the guys who are doing car stereo install all day every day know their business and are aware of the ins and outs of the various stereo interfaces.

By all means get him to fix it ...... it is his problem.

But if he fails you know the answer.

FollowupID: 860443

Reply By: Member - Outback Gazz - Tuesday, Nov 03, 2015 at 19:49

Tuesday, Nov 03, 2015 at 19:49
Howdy All

Yep !!!

Only takes one wire in the wrong place to cause headaches - bit the bullet and drove the 160 k return journey to the auto sparky and after a bit of testing he found the problem. Easy fix and I'm on my way - he explained where he went wrong but it's beyond me - quickly apologised and I'm a happy camper again !

Thank you very very much to all who replied - appreciate it !!



AnswerID: 592315

Follow Up By: TomH - Tuesday, Nov 03, 2015 at 21:10

Tuesday, Nov 03, 2015 at 21:10
Would be nice to know what was wrong with it. So many ask for advice and never tell us the result.
FollowupID: 860471

Follow Up By: Member - Outback Gazz - Tuesday, Nov 03, 2015 at 21:54

Tuesday, Nov 03, 2015 at 21:54
Howdy Tom

As I said - it's a bit beyond me but from what I understand he's picked up/ joined into a non factory wire of some sort which he thought was part of the standard factory stereo wiring ? Could be telling me porkies but it's working now and I'm happy . He did tell me from the start that audio units are something that he hasn't done a lot of but as I know even less than him I had to have faith !

Funny how such little things in life have such a big impact !

All the best


FollowupID: 860472

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