Author Topic: dash lights switch off when ignition is turned on! (Read 18755 times)

rubadubdub · « **on:** May 07, 2007, 04:05:59 am »

The quest to iron out the niggling problems with the new car contines but this one's got me stumped.

With the ignition off and light switch on, the dash illumination and electric window buttons light up.
With key turned either to first position or ignition on (lights still on) the dash illumination goes out while all the other controls light up. These include the fog light or heated rear windscreen button (cant remember which) and handbrake warning light, plus all the dash LEDs. The heater controls never light up but may just be a bulb.

I suspect a previous owner has fiddled around with these and got some wires mixed up but ive no idea where to start looking. Any ideas? Headlights work as normal BTW.

jtanguay · « **Reply #1 on:** May 07, 2007, 04:47:30 am »

sounds like your ignition switch is on its way out...

burn_your_money · « **Reply #2 on:** May 07, 2007, 06:48:50 am »

If not that then the headlight switch

rubadubdub · « **Reply #3 on:** May 07, 2007, 03:37:21 pm »

cheers guys i'll have a go at changing them and see what happens.

jtanguay · « **Reply #4 on:** May 07, 2007, 04:09:41 pm »

did you have this problem when you bought the car? or did it just start happening recently?

Vincent Waldon · « **Reply #5 on:** May 07, 2007, 05:42:17 pm »

Grounds grounds grounds... with wonky electrical things like "it's on but it is supposed to be off" or visa versa it's almost always a grounding issue. The PO monkeying with some wires is a huge clue.

Luckly the clever engineers at VW colorcoded them brown, well, most of them. On the left side of the firewall around the fusebox you should see a number of brown wires and they should run to the chassis somehow... I've seen them all in a harness and also a whole ring of spade lugs in a circle around a central screw (pretty sure that was an American A1... the German ones tend to use different connectors.).

In this case I'd be checking grounds that run in the direction of the headlight switch but most importantly the dash cluster... you may need to pull the console and the cluster and then work backwards with a test light.

My experience is that it will either be very easy to find (a brown wire dangling from an obvious ground jack) or very difficult (an intermittant connection that disappears when you pull the dash apart and then magically reappears when you put it all back together again).

Just my 0.02 worth,

Vince

rubadubdub · « **Reply #6 on:** May 08, 2007, 02:56:53 am »

Car was like that when i got it but i know the last owner fixed an indicator and tried to fix the rev counter so i was wondering if he could have altered anything.

I did suspect the ground as previous advice i received when my '83 Mk1 golf cluster went haywire was to check it, and if its not complete then drill a hole into the car body, screw in a cable and run it to the dashconsole multiplug ground, making your own ground effectively. It was supposed to be a fix when the rev counter, fuel guage, temp guage and LEDs all stopped working. Checking the voltage stabiliser was also suggested, but cant see that affecting the headlight switch in this case.

Ive seen that cluster of grounds you mean on my mk1 behind/visible from underneath the glovebox (LHS-> UK), they called it a rosette on the mk1 forum.

Does anyone know where the interior ground cables all earth to? Is it to the side of the cylinder head? If im trying to find a break would be good to know where it ends up.

MaxHedrm · « **Reply #7 on:** May 08, 2007, 03:16:03 pm »

I have the exact same prob in my Jetta. I haven't done much past replacing the headlight switch.

Some more detail in my case at least, the cluster has power when the ignition is on, but the headlights are off (the clock works) and when the headlights are on, but the ignition is off (the clock works). Only when both are on, does the clock stop.

I guess I'll look around for some dangly brown wires.

rubadubdub · « **Reply #8 on:** July 03, 2007, 06:20:10 am »

OK. Finally got round to taking the dash apart. Used a multimeter to check that the headlight circuit was ok and testing red to brown wires on the headlight switch i got a steady 12.6/7v so it looks like its ok.

Nevertheless i cut the headlight brown wire, installed a wire connector between the two cut ends and also added another wire which i screwed into a metal bracket behind the dash to provide another earth. Got same result. I did this with both the dash cluster earth wire and the headlight switch earth wire. I left the dash/lights with these extra ground wires in place, so hopefully this rules out a bad ground problem.

Unfortunately theres still no difference: Key in but not turned, with lights switched on, dash lights up fine. Key turned to first position or start with lights switched on, the dash cluster lights go out.

There are nearly a dozen wires coming out the back of the headlight switch and heavens knows what theyre all for (suggestions?). Are any of these likely to be the culprit or should i be looking at the ignition switch as previously suggested?

jtanguay · « **Reply #9 on:** July 03, 2007, 08:50:38 am »

to test the ignition switch, just bypass it by jumping the yellow wires

sort of like what the remote starter does.

rubadubdub · « **Reply #10 on:** July 03, 2007, 03:50:14 pm »

Will take a look at it tomorrow. The car starts fine so im assuming jumping the yellow wires will simply start the car.

All the other stuff thats supposed to come on (parking lights, license plate lights) when the light switch is on stay on when the car starts, only the dash lights go out.

I also noticed that when i switch the lights on the fuel and temp guage rise a little, then go down again if i switch the lights off!

Did i mention how much i like electrical problems?

jtanguay · « **Reply #11 on:** July 03, 2007, 04:37:33 pm »

the yellow should be the accessory power (for radio, lights, etc)

sounds to me like the PO did some messing around...

rubadubdub · « **Reply #12 on:** July 06, 2007, 07:30:28 am »

I think i may have solved this. Took a look at the wiring diagrams in the Bentley to identify the yellow wires JT was talking about and realised lots of the stuff thats playing up is fed by power from the voltage stabiliser.

I removed the dash (again) tested voltage stabiliser and got normal readings with lights off, but ridiculous figures once they were switched on. On closer inspection i found the printed circuit board was ripped next to the stabiliser taking out 3 of the metal tracks.

Anyone know if its possible to fix these?

jtanguay · « **Reply #13 on:** July 06, 2007, 08:00:46 am »

that shouldn't be too much of a problem... you need to use something sharp to take off the outer layer to expose the metal, then you need to use something to make the connection, and make sure that they don't touch.

Darth Garry · « **Reply #14 on:** July 06, 2007, 09:00:34 am »

If you could get the circuit down to the metal, you can probably find an electrically conductive epoxy of some form. With careful application it should work, or find another cluster. I don't think you can soldier these things.

http://www.mgchemicals.com/products/8331.html

Good luck!

Garry