HELP Please - Weird Electrical Problem on 4x4 Saph Cos

[Kevin B]

Good evening all My 4x4 Saph Cossie has developed a weird electrical problem and I am hoping someone may be able to help out with some ideas... Basically when I'm driving along and put the indicators on, or touch the brake, the power to the stereo cuts for a split second, and the rev counter flickers or doesnt read true engine revs (until indicators are cancelled). Only developed this problem on the way to Central Meet at the Pod a few weeks back. Someone suggested it is likely to be an earthing problem so Ive cleaned the main earths under the bonnet, and also behind the dash and in the footwells but this hasn't made any difference. If anybody is able to shed any light on this for me I'd be really grateful Cheers

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[dojj]

indicators and brakes means the most likely culprit is the wiring loom that goes form the reverse light switch and up along the gearbox to the bulkhead behind the head
unplug the 8 pin multi plug and see if it solves the issue, there should only be 3 wires in the plug though

[Kevin B]

So in addition to the reverse lights does that loom control something else too? Thanks for the suggestion though I will take a look at that tomorrow

[v man]

nothing weird about a cossie developing some sort of problem

its when they dont it becomes weird lol

have a check to see if all the earthing points are good also

[Kevin B]

What other earthing points mate? Checkes ones under bonnet and behind dash closks / footwalls etc...

[v man]

Originally Posted by Kevin B

What other earthing points mate? Checkes ones under bonnet and behind dash closks / footwalls etc...

there are various earthing point around the car mate

just follow the wires and you will pick them out

[Kevin B]

Cheers V Man - will keep looking...

Any more suggestions - must have happened to someone else??

[martysmartie]

I bet it's an aftermarket head unit?

I would trace back the radio wire ground, I don't know if the instrument cluster etc shares the same ground, probably as it's in close proximity of each other, if so it's worth checking/cleaning this, it's most likely corroded.

Martin

[Kevin B]

Thanks again for the suggestions guys, its much appreciated

OK slight update - in addition to cleaning the earths under the bonnet (behind each headlight, battery tray, inlet, behind battery, bonnet) we've cleaned the ones behind the dash clocks that are mounted to the steering column support plus those in the the side of the footwells and the gearbox to chassis earth.

Looked for some in the book for the rear lights (as someone suggested this could be a fault) but they are earthed through the loom that heads towards the front of the car. Cleaned the terminals just in case though.

Suspect the stereo earths are those on the steering column support so thats them cleaned, will unplug the reverse light switch and try that. The headunit uses the original loom so will unplug that aswell and see if the fault disapears.

With the engine running, the moment you put indicators on the dash lights go dim and pulse in time with the indicators. When you touch the brake pedal they go dim as well and return to normal again almost straight away (even with foot still on brake). The rev counter also flickers either when brake pedal is initially applied or when indicators are turned on. The hazards however have no effect on either, nor do the wipers?

Any other ideas?

[Kevin B]

Forgot to mention - couldnt get the headunit to loose power up either by touching the brake or putting indicators on so maybe cured that... either that or just decided to work tonight?

[Kevin B]

Going to get meter and test the wires as majority of earths are now clean and it hasn't made any difference but there could obviously be a break somewhere. Removed the headunit to see if this was causing any problems and this also made no difference so think I can rule that out too.

I need to source a wiring diagram as my workshop manual doesn’t have that in it. Dont suppose anybody has a .pdf they can e mail me in return for my eternal gratitude??

[DAN-Saff]

I've got the kind of problem with mine but its the battery light dimly glowing when I have the lights on. I've cleaned and checked the earths and no difference. I did find high resistance on the earth of the drivers rear light which temp earthed out but still had the problem I am looking into that but want to find the bat light problem and hope to stumble across the other one at the same time.

[Iain Mac]

My weird electrical problem is that, with the car parked in the garage and no keys in it, every now and again the ABS pump fires up for no obvious reason.

[Smit]

Originally Posted by Iain Mac

My weird electrical problem is that, with the car parked in the garage and no keys in it, every now and again the ABS pump fires up for no obvious reason.

Does it turn off again though?

I had this problem with mine (didn't turn off) even with the keys out.. Turned out that the ABS wiring loom had got hot and melted where it goes through the bulkhead near the ECU.. Pulled some slack out into the engine bay and seperated the wires (4/5 had melted together) and heat shrinked them. Problem went away

Kev - Have you tried taking the fuse out of the box for the interior power? (think it's 28) as the lights/dash etc won't run on the same relay.

[Iain Mac]

Originally Posted by Smit

Does it turn off again though?

Yes, it just runs for 2-3 seconds and stops.

I'm finishing putting the interior in today, then fitting the spare propshaft, getting the exhaust back on and taking it for a spin because it has been parked up for a couple of months now.

[RS500/364]

Originally Posted by Iain Mac

My weird electrical problem is that, with the car parked in the garage and no keys in it, every now and again the ABS pump fires up for no obvious reason.

if the main loom under the dash is wired to a battery direct makes the abs WHICH SHOULD TURN ON AT POSITION ONE stay on perm but the abs will only be heard as its primed ! but is always turned on

maybe not explained 100% but i had this up till a while back does you battery drain !

[Iain Mac]

I think the battery does drain, but the car is only used now and again so it is usually plugged into a CTEK.

I haven't changed any ABS wiring, but this sounds like it could be a job for a sparky.

[martysmartie]

Originally Posted by Iain Mac

My weird electrical problem is that, with the car parked in the garage and no keys in it, every now and again the ABS pump fires up for no obvious reason.

Somehow you pump has got a permanent live, opposed to being switched via ignition pos 1, and yes this will drain the battery!

The pump switches off when the system is at the correct pressure, the same as it does when driving etc, if you were to push the pedal a few times you will hear it activate.

Martin

[RS500/364]

easy to sort if you want to spend 3 hour dash in out wire tidy up shame you are so far !

[Iain Mac]

I've just refitted the dash after converting the tunnel and I'm not taking it out again! I'll live with the pump priming now and then!

[martysmartie]

You shouldn't need to remove the entire dash, the passenger 'lower fascia' should be suffice I would have thought, which isn't too big a job to remove.

Martin

[RS500/364]

Originally Posted by martysmartie

You shouldn't need to remove the entire dash, the passenger 'lower fascia' should be suffice I would have thought, which isn't too big a job to remove.

Martin

then you are going to be fiddling following wires you cant see properly do it right 1st time !

[arse end happy]

i know it sounds silly but wots the volts on battry back from alternator

[martysmartie]

Originally Posted by RS500/364

then you are going to be fiddling following wires you cant see properly do it right 1st time !

It depends imo, it should be fairly easy to spot where someone has done such a massive bodge, just be removing that section of the dash, seen as this is where the components are, at least this would be my starting point!

Also to OP, it may be worth looking at the battery terminals etc to see if someone has dangerously just run a direct live, in either that or back of ignition etc!

Martin