Club 80-90 Forums

Evening all

Can anyone make any suggestions as to what might resolve the following problem:

1981 2l Aircooled cu

The dashboard lights work ok when the engine is off: i.e. No key in ignition, turn on lights, three dashboard lights come on, one a bit dim but all working, dimmer working fine.

Same procedure with ignition on or engine running and no dashboard illumination. Bothersome, as its when you're moving that you need to see the speedo, not so necessary when stationary!

Sounds like the usual crazy behaviour that occurs when you have a bad ground.
As a matter of interest - does your fuel gauge work ok?
And does your highbeam indicator light work ok?
(Both use the gauge ground to function - so if you have a problem it usually also makes those items misbehave)

Hi MLC, thanks for the response.

The fuel guage works, after a fashion (it never drifts above indicating half full, but then never has in the 8yrs i've had the van); and i think the main beam indicator light (yellow) works ok, but will need to go and check that also tonight.

When you say "bad grounds" are you suggesting checking the "crowns" as suggested in the wiki section (VW Electrics bad earths)? I'll have a look when i get home later. I'll try that and then maybe think about new ignition as suggested in the wiki (Talk:VW Electrics bad earths)

Ta

Kev

Yep - the earth crowns that live above the fuse module thingy behind the glovebox.
My thoughts are that with the power off to the dash (i.e. No ignition) then the illumination lights are finding a path of sorts to ground through the voltage regulator in the dash but when the dash is getting 12v (ignition on) then that path goes away ......
Hence why I asked about the fuel gauge (as that is powered by the voltage regulator) and the highbeam light (which needs a good dash ground to function correctly)

But I'd certainly start with a good clean up of the earth crowns - see if that does any good.

As an interesting test you might try: ignition off, dash illumination light on (which works fine, right?), then pull the highbeam flash stalk to flash the highbeams (with ignition still off & dash lights on) and see what that does to the dash illumination lights ...... that might yield some useful information??? ... Maybe ....

Earth crown cleaning will have to wait until the weekend, however, i have tried the "interesting" test:

Ignition off, headlights on, dash lights up ok (however, the headlights look pitifully weak, but i'd always previously associated this to "not having the engine running). Pull up main beam stalk and there is a world of light outside, dash main beam "yellow" light is illuminated and dash lights stay lit.

Turn ignition on, headlights are brighter (to be expected),but no dashboard lights

Will report back after weekend

I feel epic.

Earth crown located, only one, must be because it is an old bus. Stripped down and cleaned with wire wool. reassembled and hey presto, working ok. I now have dashboard lights even with the engine running. How novel!

Cheers for the help, all sorted now. Well, sort of. There is still a bit of weird behaviour where it stopped working again after 10 mins, until i took the fuse out of leisure battery split charger, but i'm not sure that is related and ill keep an eye on it.

All sorts of connections will need the same treatment.
Particularly in the fuse and relay box.