Temp and Fuel Gauges Acting Flaky.....Voltage Stabilizer?????

[ftm1776]

’91 Jetta normally aspirated diesel. I am the original owner. 253,000 miles. Water temperature and fuel gauges acting flaky.

First I had intermittent problems with the engine instrument warning lights(alternator, temp, oil) and the gauges. The gauges and lights would occasionally go “dead”. No gauge indications or warning lights. The blue high beam indicator would still work. All other electrical functions seemed normal. Finally, the gauges and warning lights went dead permanently.

My first thought was that the ignition switch could be bad. I replaced the ignition switch, as an easy fix, and this seemed to bring back the warning lights. The warning lights are now fully functional.

However, the fuel and temperature gauges are acting flaky. The temp gauge does not come up to its normal hot position when the engine is hot.

With the tank full, the fuel gauge slowly climbs to about ½ full, then, falls to about ¼ full and drifts somewhat between the ½ and ¼ marks!!!!

This may be a “voltage stabilizer” problem, but I thought with it being a solid state device(?) that it would either work or not work??

Where is the voltage stabilizer?? How does one access it? Does the instrument panel have to be pulled. I see there are 7 screws holding it in place(in Bentley's). It looks like the switches, radio, climate panel have to be removed, but I’m not sure. I’ve reviewed my Bentley’s, but some detail is lacking. Like where the stabilizer is located.

I did have to replace the voltage stabilizer on my 1978 Rabbit. However, I don't think I had to remove the instrument cover to do it. I have removed the “knee bumper” in my under the dash so I get a good view from underneath up into the back of the panel cluster. I see the back of the speedo and clock.

Has anyone else done this job? Comments, tips would be appreciated.

[catlin_cava]

If its like an MK3 the Voltage Regulator is in your altenator. My Gauges where jumping on my cluster on my current build when I hooked the battery up. once I hooked the Altenator up everything acted normal

[rubadubdub]

Voltage regulator is in the alternator.  The voltage stabilizer is a little microchip thing about 5mm by 5mm with 3 prongs coming out of it.  If memeory serves one is 12v feed, 10v (?maybe) output and the other ground.  If you remove the instrument cluster its attached to the plastic circuit board in one of the corners, i think its a top corner.

You have to remove the cluster to get at it. Clean the main ground wire in the multiplug connector while its out too.

[ftm1776]

Voltage regulator is in the alternator.  The voltage stabilizer is a little microchip thing about 5mm by 5mm with 3 prongs coming out of it.  If memory serves one is 12v feed, 10v (?maybe) output and the other ground.  If you remove the instrument cluster its attached to the plastic circuit board in one of the corners, i think its a top corner.

You have to remove the cluster to get at it. Clean the main ground wire in the multiplug connector while its out too.

My '78 Rabbit had the little square stabilizer with 3 prongs and held in place with a screw. I'm a little mystified by what kind of stabilizer I will find in my '91 Jetta. There are two pictures shown, more or less, in my Bentley manual, chapter 14, page18. It seems that there has been a change since 1978.

Question, Rubadubdub: which :to which multiplug connector are you referring???



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[rubadubdub]

The one which plugs into the bottom of the dash instrument cluster.  There are about 10 wires in a plastic clip and the earth is one of them.  On my mk2 it was at the very end and a brown wire.  It's worth just checking this first with a multimeter to make sure its got continuity with the car body (earth), as it'll save you chasing after weird electrical faults that are just down to a bad ground.

Those 2 pics you are looking at in the bentley are exactly what it looks like.  You may have to remove the odd screw to peel back the circuit board but its pretty self explanatory once its out and in front of you.

The bentley one is better but anyway here's a bad picture of the back of the board where the 3 prongs slide into (top right):
http://www.vwdiesel.net/forum/index.php?topic=8085.0

[ftm1776]

Rubadubdub:

Yes, I've accessed the back of the cluster and there is the little sucker! The little black stabilizer and the blue printed circuit just as it shows in Bentley. I was confused by the lower picture in Bentley but now am clear. I'm on my way to the parts guy for a new stabilizer and panel lights.

The wiring harness connector with many small wires is what I thought you meant. Good tip on checking the ground there. Brown seems to be a standard ground color for VW. I was in my '71 Super Beetle too. I had the Beetle for 25 years.

I'm thinking of disconnecting the speedo cable at the tranny to avoid any damage at the speedo and because it looks easier to re-assemble after this surgery.

Thanks for the tips and comments.

These forums are invaluable. I can imagine this being a $200 job at an independent shop and maybe $400 at the dealer! ! Maybe I'm a little off on those figures, but you get my drift. Thanks again.

[neimis]

If the cluster is anything like the Passat B3 clusters, before you put it all back together you might want to take a look at all the solder joints on the board. It's fairly common for the Passat boards to develop cracked/dry joints, which can be remedied by simply resoldering them. The dry joints can cause the same symptoms that you described, and in fact the last time I replaced the voltage stabilizer, it didn't fix my problems, so now I need to go back and do the resoldering.