[shawn]

Right, this started as a simple job of replacing a broken speedo in Denise's 1971 1300 bug.

Took the old one out and put the new secondhand replacement back in making sure the wires went back where they came from.

Started the bug up and the dash lights started doing everything wrong!

The generator light stayed on, the indicator warning light was flashing reagrdless of whether the indicators were on or not. The speedo illumination lights don't work, the fuel guage reads half full regardless of the amount of fuel. And when I went to turn the car off it kept on running.

Cured the running on by tapping the wiring, not ideal but it worked and the car starts and runs as it should,so at least she can get to and from work using the sat-nav as a speedo to avoid tickets but I'm really frustrated I can't fix this.

All the lights work correctly on the switches, even the indicators. It is just the warning lights in the speedo.

I removed the replacement speedo and put the old one back in and still have the same problems.

I've been scratching my head all afternoon to no avail.

So I've had to admit defeat and ask for help...please

Thought it was an earth issue so replaced that by earthing with a fresh wire to the chassis and it still doesn't work.

The wiring looks bit of a mess with various bits added over the years.

At a guess I would say it is a short circuit somewhere but I lack the skill to work out how to rectify this one now.

[Andy]

Only just seen this, sorry

You have a missing earth for my initial guess. You have all the symptoms of it (I know you said you have put one on, but please carefully check)

Current will always take the easiest path to earth, and you get it backfeeding which will cause some very very odd things to happen.

Mixing up something like the generator or fuel gauge wiring etc will also cause this kind of 'effect' as current will simply run where it can.

Try not to run the engine with the alternator light disconnected as you will damage the alternator if you do this. Typically (I'm assuming an alternator with a built in regulator, if dynamo or external regulator ignore this) the wiring for the alternator light is an ignition live through the bulb and the alternator earth's it to put the light out. If this little wire from the alternator is in contact with earth, it will fry the internal regulator.

Not too sure what else to suggest without seeing it, its possible you have a shorted (internally) bulb holder which could cause some odd effects.

Carefully check the fusebox wiring etc as its really easy to disturb it, would not take much to catch something in the speedo replacement process.

EDIT... Check you have an earth lead from the speedo case to the body that could cause some odd problems if its missing.

This post has been edited by Andy: 24 May 2010 - 07:44 PM

[shawn]

Cheers Andy, its still running the old dynamo so hopefully no bulb won't matter for now.

Either way its going to have too wait till the weekend now as I have a pretty hectic week till then.

I'll let you know how I get on

[Andy]

No problem.

I do no think it will be difficult to fix, it does sound like a missing earth lead or possibly a power feed in contact with something it should not be.

[shawn]

I'm hoping to have a look this Friday afternoon, so can you just confirm a few bits for me in advcance of then.

How do the speedo bulbs earth? It would appear that the dash illumination and the main beam warning bulb are earthed through the case where the screws at 3 and 9 o'clock positions hold it in place. These two screws each hold a couple of other brown (earth?) wires so I'm assuming they are earhts for some other electrical circuits.

Then there is another earth for the 3 bulbs at the bottom, oil, charge and indicator. It is these three I'm having probs with at the moment. Are these earthed by the small brown wire that seems to come from the fuel sender? Not sure on this one but even trying to earth these straight to the body made no difference to the problem.

And can I confirm that the fuel gauge bits should be connected by a thin black wire that goes to the tabs on the trembler and the other tab on the back of the fuel gauge, both of which seem to have a small nut securing them.

Thanks for the help.

As you say, its bound to be something easy but its finding it that has me stumped at the moment...

[Andy]

I'm struggling to visualise it as the last one I had was a 1303 and that's wired a bit differently as it has a dashboard as such.

I'll provide these links though:

http://www.vw-resource.com/speedo.html

http://www.vw-resour...edo.html#wiring (more relevant)

[shawn]

Hi Andy, where do I begin.

For some reason the wire that feeds the indicator warning bulb is permantly live which seems to be causing the problem. But can't work out why??

As for the charge light, bypassing the fitted wire from the voltage reg to the charge light still results in this light coming on only when the engine is running despite a healthy 13(ish) volts at the battery, the light won't come on with the ignition raised as it should.

I have nothing at the oil warning bulb.

And the fuel guage is still showing 1/2 a tank even though it should be nearly empty!

I tested all the bulbs in the dash by sitting in the back of the car next the battery taking power and earth direct from it with jumper wires.

After refitting the speedo I replaced the earth with a fresh wire to a known good earth point checked with a voltage meter and power from a known live fuse.

I think I might have replaced a wire to the wrong terminal on the back of the fuse box when I originally changed the speedo but can't remember which one and in so doing fried the other circuits but am stumped as to which wire it was. I suspect that I damaged the voltage reg and possibly the oil warning switch but don't know how.

I've asked Brian Terry at Volksfarmers to cast a quick eye over things tomorrow when I collect my 412 so fingers crossed it will be sorted soon.

PS As for the speedo cable that looks like it broke. Strangley it only turns when at a particular angle which is why I missed it before.

[Andy]

Hmm

I do agree you probably just have something really simple wrong like a wire on a wrong terminal on the fusebox, which can cause all manner of strange effects once current starts backfeeding around

My speedo cables (I've only had to change two though, one on each car) break at the wheel / hub end typically in my case, I think poor routing can not help although they can just break anyway, the other common failure is the hubcap square hole that the end of the cable sits in rounds off resulting in the speedo slowing then stopping totally, temporary 'fix' is to araldite the cable where it protrudes though the hub cap to the cap (tiny matchstick head blob is plenty) although this only tends to last a month.

I did once have a really good pic of the wiring as viewed from under the bonnet on your model too, but I am unable to find it

Having said that I have found this, although US spec, it may help.



And some links that may help too.

http://www.shoptalkf...ic.php?t=112390

http://www.volkszone...ad.php?t=592182

http://www.volkszone...d.php?p=6510408

http://www.thesamba....c.php?p=3470485 (scroll down to later speedo pics)

[shawn]

Thanks for the help Andy...a tad embarassing but it was my little ommission from my original picture that was the problem.

Basically I marked on my little pic a 'B' on one of the fuel guage tabs and forgot it was 'B' for brown not black

The lights all work now and so does the fuel guage. Just need to order another speedo cable to replace this broken one.

[Andy]

Good to hear its fixed, that's the important thing.

That black vs brown if you just write B down, I know what you mean , easily done really. I've done similar with bits and pieces, it happens.

Easily 'fixed' too as you found.

At least the speedo drive cable will be straightforward now