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andrew_jo

Mk2 Polo warning lights and gauges not working

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andrew_jo

Hi, I have a 1990 Polo (1 litre engine). The fuel gauge and temperature gauge occasionally used to stop working whilst driving along. This was an intermittent problem and apparetly happened at random. When it happened, it would last an hour or two or maybe till the next time the car was started. However about a week ago it became permanent. So now the fuel gauge and temp gauge are permanently not working. This problem also affects the cluster of warning lights in the middle of the instrument panel, but does not affect the time clock or the speedometer. All other electrics (eg, external lights, internal lights, wipers, etc are working fine).

 

Anybody have any ideas what the problem might be? I am quite happy to dismantle the instrument panel, I just don't know what to look for after I do that. I'm hoping somebody can give me a few pointers to find the cause.

 

Thanks

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nige8021

That sounds like the voltage stabiliser unit in the speedo has died,  Try VW Heritage they probably will stock them

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andrew_jo

Thanks for the advice.  VW Heritage don't have them.  Actually I can't find them anywhere so far.  Will continue searching.  Thanks again.

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caretakerplus

Welcome to the Forum.

 

If it proves impossible to obtain a voltage stabiliser, you may be able to obtain a unit that could be wired in there, but would probably NOT fit into the same physical space - also you may have to pay more for it.

You could ring your local RS Components and ask if they can recommend anything. If you simply look in their catalogue, you would possibly end up seeing something like Stabilised Power Supply Units - something that you definitely DON'T want!

 

Regards

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andrew_jo

Thanks for the comments you posted.  I have actually now fixed the issue. In case it's of any use to anybody else, this is briefly what I did:

 

First I searched around for a suitable voltage stabiliser.  That took a long time but I finally I figured out that I could use the same voltage stabiliser that was detailed on this page: www.cabby-info.com/gauges.htm.  From that page, I got the "Type" of the voltage stabiliser, and then I located a replacement of the correct type (KA7810AETU) on Ebay.  I ended up buying this one:

https://www.ebay.co.uk/itm/ON-Semiconductor-KA7810AETU-Voltage-Regulator-1A-10-V-3-Pin-TO-220/173386050782?epid=9021013911&hash=item285e9d2cde:g:JPEAAOSw5KFbNmV4

 

Then I removed the instrument cluster from the dashboard.  This was straightforward, but slow-going because obviously there wasn't much physical wiggle room.  Once I had removed the instrument cluster, I located the voltage stabiliser and removed it.  It's not soldered in, just push fit.  I removed it and tested it.  It actually tested fine.  But I assumed my test must have been flawed, or the voltage stabiliser was only working intermittently, and I went ahead and fitted the new one I had bought.  I also tested the new one before I fitted it, and it was also fine.  To fit the new one, I needed to bend its legs into the correct position, and break off one of the plastic locating tabs on the instrument cluster.  Eventually I was able to fit it and attach it to the original heatsink.  I re-assembled the instrument cluster back into the car, re-connected battery and turned on the ignition and guess what ... it still wasn't working.  In fact nothing had changed - the problem with the warning lights and gauges was still there.

 

After a lot of head scratching and a lot more internet seaching, I chanced upon this post:

http://www.methodbook.net/electronics/polo.html

 

It seems I had an almost identical problem to the author of that page.  I say almost identical because he was also getting a discharged battery, but I was not.  Anyway he describes what he did, and basically I did the same thing - fitted a "shunt" wire to the instrument cluster circuit board to bring power directly from the live feed to the voltage stabiliser.  After refitting the instrument cluster, it now works fine.

 

So it seems the root of the problem was a broken connection within the circuit "board" which is attached to the back of the instrument cluster.  Actually it's not a board as such.  The printed circuit is embedded within a flexible plastic sheet, and sort of wrapped around the back casing of the instruments.  It's not readily repairable.  I guess it is deteriorating over time.

 

Anyway my repair seems good, it has been working fine for a couple of weeks so far.  Thanks again to the people who responded to this post.  And to the guy who wrote the blog I mentioned above.

 

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