weird electrical fault

[Richmassey 10]

I hope someone can help with this fault on my 1994 2.0 8v corrado,the battery discharges in about 4 days and I have found the following weird things with the electrics. the heater blower and windscreen wipers work with the ignition key turned off and the digital dash never goes out also now and again the electrics just go off with no power until you remove a lead from the battery and then put it back on. I have traced it all using the manufacturers handbook using a test light but even taking all the fuses out the light stays on so its drawing current probably to the dashboard,this all points to the ecu.

has anyone else had aproblem like this?

if you think it could be the ecu has anybody got one for sale to fit mine, have heard you might have to recode it to your car? is this easy to do

hope to get it solved. apart from this fault its a great car with leather interior and everything else works

cheers

Rich

[vw rule 19]

Hello Rich,

 

possibly could be your ignition switch is playing up,

as they can cause a few problems.

What happens is the inner contacts burn out,

or wear down causing a continuous current,

even when you've switched the ignition off via the key.

 

The ECU only controls the engines sensors like the ignition / fuel system,

there's one ECU for the engine in the engine bay,

and there's another one inside the car for the ABS braking system.

You should have power from the battery to your fuse box part of which is not powered until the ignition is turned on via the ignition switch,

you might have to check the wiring from the ignition switch to see if the switch is working correctly.

you should have continuous power to your radio and possibly your dash LED clock, apart from that everything on the dash should be off,

if the dash is still lit up or has power then something is telling it to stay on.

I had a fault very similar to yours,

and my problem was the ignition switch had burnt out causing a continuous current, which kept my ABS light lit.

 

 

Hope this helps

 

Si

[Richmassey 10]

Hello Rich,

 

possibly could be your ignition switch is playing up,

as they can cause a few problems.

What happens is the inner contacts burn out,

or wear down causing a continuous current,

even when you've switched the ignition off via the key.

 

The ECU only controls the engines sensors like the ignition / fuel system,

there's one ECU for the engine in the engine bay,

and there's another one inside the car for the ABS braking system.

You should have power from the battery to your fuse box part of which is not powered until the ignition is turned on via the ignition switch,

you might have to check the wiring from the ignition switch to see if the switch is working correctly.

you should have continuous power to your radio and possibly your dash LED clock, apart from that everything on the dash should be off,

if the dash is still lit up or has power then something is telling it to stay on.

I had a fault very similar to yours,

and my problem was the ignition switch had burnt out causing a continuous current, which kept my ABS light lit.

 

 

Hope this helps

 

Si

 

Thanks for that,in all the paperwork that came with the car(and there was a lot) at some point it has had a new ignition switch but I also disconnected the plug to the switch but it still kept the mileometer and power on as before ,forgot to say the radio looses it memory as well when the ignition is turned off. The wiring diagram also shows a live from the starter motor to the loom as well perhaps it might be that and got to say it's driving me mad cheers Rich

[vw rule 19]

Right sounds like something has shorted out.

does everything work ok on the car,

does it start up ok.

 

Could be a relay or control unit,

theres a lot of electrics that can share / go through the same control unit.

 

But it does sound like something has shorted out.

I'll have a look in my Bentley manual.

 

Your radio should keep it's memory once the ignition is switched off,

so there is something a miss.

 

 

Hope this helps

 

Si

[vw rule 19]

Just had a thought what head light switch have you got fitted is it the original one,

it's just that the original style switches can get quite hot,

and melt inside melting part or all of the headlight wiring loom,

which can cause other errors as the wires will then fuse together.

Again this happened to me back in 2006.

 

 

Si

[vw rule 19]

You've got black negative (earth) cable 25mm thick from battery to body,

also a brown 4mm thick wire goes to the fuse box,

it fits in Z2 which is top right looking from the back,

or top left looking from the front, it's a single spade connector.

 

The red positive (live) cable 25mm thick goes from battery to starter motor,

then red 6mm thick live cable from starter to alternator.

A 6mm red positive battery wire goes from battery to back of fuse box,

it fits in Y3 which is top left of fuse box looking from the back,

or top right looking from the front, it's a single spade connector.

 

That's your main power supply to your fuse box.

 

 

6 contacts on ignition switch.

looks like 5 are used,

looking at the connector plug face on.

 

Bottom left (15) is brown wire I think.

Bottom right (X) is black / yellow wire

Middle left (50) is red / black wire

Middle centre (30) is red wire

Middle right (S) or (SU) is brown / red wire

 

Looks like (X) goes to the load reduction relay which is number 4 relay in the fuse box.

Bottom right relay is the fuel pump relay which is number 12 just above fuses 20 and 22

 

(50) goes to the starter motor.

(30) looks like power supply from battery (so when ignition switch is turned on it completes the circuit and turns dash lights on)

(15) is on circuit 36 which looks like is a shared earth or something with the ABS warning sensor switch, brown wire I think.

 

Looks like as well from alternator the charging circuit passes through the instrument cluster wiring loom.

 

Check load reduction relay.

check alternator operation.

Check you have power and correct earth to starter motor.

 

Something is staying on or has burnt out possibly.

 

 

I'll have another look tomorrow after work if I have time.

 

 

Hope this helps

 

Si