Dash lights dimmer issue (solved)

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Paul773car
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Dash lights dimmer issue (solved)

Post by Paul773car »

Evening all

So tonight I pop out in the van to pick up my daughter and I have no illumination on the dash. So I can't see the speedo or the fuel temp gauge. Everything else works fine. I move the dimmer switch thinking I have probably moved it but it makes no difference. I notice that it's very loose to move so remove it and the sliding armature seems bent up away from the rheostat. I have a spare so I slot that in still no lights. Then I notice smoke so pull the switch out quickly looking at the replacement the armature on that has burnt up. Any ideas what could be causing this seems like way too much current is flowing through the switch?

Thanks

Paul
Last edited by Paul773car on 28 May 2021, 16:10, edited 2 times in total.

Paul773car
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Joined: 08 Jul 2019, 14:26
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Re: Dash lights dimmer issue

Post by Paul773car »

Just thinking about it my heater control light has never worked but it's never bothered me. I wonder if the live to the heater panel has come loose and grounded itself hence the current being so high to melt the armature.
Will have a look in the morning.

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Robsey
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Re: Dash lights dimmer issue

Post by Robsey »

I would think that if it is enough to melt the interior of the dimmer switch, then it is likely that a high current drawing device has possibly developed an earthing problem.
Causing voltage to track through the rheostat instead.

I would suggest looking at all of your looms around the instrument / switch area for damage to the wiring or a rusty / burnt-out connector.

I am surprised that 'nothing' else is affected.
The current has to be coming from / going to something else.
There really isn't that much current (relatively speaking) in the dimmed-illumination.

3 dash bulbs, heater panel bulb, radio illumination bulbs, cigar lighter bulb...
So about 5 off 1.2 watt bulbs and any radio illumination. - barely 1 amp in total.

Just confirming - 1.6 diesel in a 1984 van.
So early fuse panel.
1983 Tin Top with a poorly DF and 4 speed DT box.
Soon to have a whizzy 1987 DJ.

Paul773car
Posts: 37
Joined: 08 Jul 2019, 14:26
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Re: Dash lights dimmer issue

Post by Paul773car »

Thanks

Yes early fuse panel. And 1.6d

Will have a proper look around after work tonight and see if I can see anything obvious

The radio illumination, does this run to the stereo multiplug? As I did have a new radio put in a couple of weeks back and haven't driven it at night since so it could be connected.

Thanks

Paul

Paul

Paul773car
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Joined: 08 Jul 2019, 14:26
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Re: Dash lights dimmer issue

Post by Paul773car »

Couldn't wait so had a quick look. Brown wire behind heater controls was loose and bare. I've taped it up and ordered a new switch. Hopefully it was that and the new switch won't just burn up but I'm not sure how I would test it another way.

My switch only has 6 terminals and the ones you can buy new from jk and tge like seem to have 8 terminals, are they interchangeable?

I bought a 6 terminal one on ebay to be sure but it was twice the price of a new one with 8 lugs.

Thanks

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sweetaswesty
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Re: Dash lights dimmer issue

Post by sweetaswesty »

I could be wrong but shouldn’t a brown wire be earthing something? So it being loose in the first place but then also taping it up would mean whatever it was supposed to be earthing isn’t earthing or is earthing in a faulty way?
I would be interested to know what someone with a better understanding than me thinks.
1991 Westfalia California Hightop1.9tdi

Paul773car
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Re: Dash lights dimmer issue

Post by Paul773car »

I think you are correct. Brown should be ground so I will have to take another look.

When I found the bare wires just thought it must be that. My van has no cigar lighter socket and the heater panel illumination has never worked so its possible the earths are from them.

Doesn't solve my issue though unfortunately. Will try again

Paul

Paul773car
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Re: Dash lights dimmer issue

Post by Paul773car »

OK all sorted but a bit weird.

So the grey blue radio illumination wire from the switch was grounded. Followed it back and it was connected to the radio plug (the vw square black one) Now the weird thing is it's been connected to that plug since I had the van as I haven't changed anything. The old radio worked fine as did the lights. I fitted a new one a few weeks back and the new radio expects ground on that pin. So the illumination feed was straight to ground (well via the radio)

Cut the cable and now the lights work as before. Radio is still working fine too. I've added a new earth wire to the radio.

So word of warning. Just because the harness fits to the old plug perfectly check you haven't got a blue grey wire going to the vw plug. Presume old radios picked up the illumination feed and maybe my old one just didnt use that pin?

Happy it's fixed but I'm annoyed I didn't check all the wires before fitting it.

Thanks to everyone who helped. I wasn't even aware there was a radio illumination connection so without that knowledge it would have taken me an age to sort and I've have burnt out another switch too

Thanks

Paul

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Robsey
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Re: Dash lights dimmer issue (solved)

Post by Robsey »

Not all radios have illumination... especially the really early stuff.

They would have been very basic -
Red - battery live.
Brown - ground
And two speaker wires.

Later stuff can have all sorts.

Black for ignition live.
Grey / blue for illumination and so on.

With brown wires. It does not matter if you short them to ground - even if nothing else appears to be connected.

You are more likely to cause electrical gremlins by leaving a ground disconnected.
Often devices with a bad earth will look for an alternative path to earth..
The most common one is faulty rear light clusters.
We have all seen old cars where indicators flash the tail lights rapidly,
Or applying the brakes also illuminates an indicator bulb dimly...

Good to know it is sorted :ok
1983 Tin Top with a poorly DF and 4 speed DT box.
Soon to have a whizzy 1987 DJ.

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