temp and fuel gauge both read high

[vandukw]

both the engine temp and fuel level gauges read higher than actual, have test eng. temp and its running within normal range and have installed new fuel sender but the fuel level indicated is almost always at 1/2 or above with only 3 gals remaining in tank, temp gauge typically past led at normal cruise. Any ideas?

[tencentlife]

Both gauges share a voltage regulator, which plugs into the printed circuit board on the back of the instrument cluster. It's very small, just a 3/8" square chip with three legs. If it isn't clipping voltage correctly you would get high scale indications on both gauges.

[wbx]

[reeves99]

Hi,
My temp gage red light flashes and the gage goes to max. Scared me the first time it happened on the highway. Then it just drops back to normal. Do you think this is electrical or is the sending unit broken? Thanks

[wbx]

[tencentlife]

Well, back to vandukw's problem: both gauges also share common positive and grounding buses in the printed circuit, but since other things seem to work, the one thing only shared by those two gauges is the voltage regulator, or stabilizer as it is called in Bentley. On 90.1, Fig.2 is the check for output. It's very easy to test, you just need a VOM. It is on the back of the tach body, and output between the center pin ground, #2, and the pin closest to the tach body should be 9.5-10.5 V with the key on. I've never seen one go out, and it would make sense to also check the grounds after each of the senders, but I could rule out the voltage regulator, the component they both have in common, a lot faster than I could track down both grounds. Besides, bad grounds would make the gauges read low, not high.

Here's a test you can do if you don't have a VOM handy. Sit in the driver's seat, key on, and turn on high beams, heat fan on hi,wipers on hi. This will depress battery voltage. Note exactly where both gauges read after a minute. Now switch everything off, and start the engine. Hold it up off idle at about 1500rpm. Do your gauges both read higher than they just did? If so, and your charging system isn't broken, too, the regulator is defective.

[reeves99]

[coastdog]

Did you ever solve this problem. I’ve got exactly the same thing. Both gauges read high when the engine is running. When you turn off the engine and keep the key in the run position they read normal...

[oceanair]

[Sodo]

[coastdog]

Still trying to solve this one. Both gauges still read high and occasionallly the fuel gauge goes to full and at the same time the temp gauge goes high and the red LED flashes and then they both come down. I’ve changed the voltage stabilizer twice and checked and cleaned all grounds thoroughly. I installed a new starter battery as the old one was starting to lose charge while sitting and was 8 years old. I’ve monitored both the new battery charging level and the new stabilizers output while driving with a meter hooked up. The battery shows a steady 13.7 volts of charge and the new stabilizer is putting out about 10 volts but when both gauges surged up, the meter read 11.4 volts. So I know the problem is caused by high voltage. Just not sure what is causing it.

I have a few ideas about where to go from here which include checking the alternator and it’s votage regulator although can’t see that being the problem since the battery was receiving a steady 13.7 v while running. Changing ignition switch as I have read that it can solve mysteries and hide problems and then changing the stock blue foil for a GW one but don’t want to do that if I don’t have to because my foil appears to be in perfect shape.

Question for anyone on here... in the first picture below, you can see the voltage stabilizer and just beside it is a resistor (I think). I can’t find any reference to that device in the Bentley other than it appears to be downstream of the voltage stabilizer in the schematic but no mention of it and it is not in any of the actual pictures of the stabilizer in the Bentley. This is not my original foil. I think it came out of a 90 or 91 and has worked perfectly for years. Just never saw this resistor before. Anyone know it’s function and could it be the culprit in the guages surging high...?

[crazyvwvanman]

The problem is likely because there isn't always a clean true ground at the ground leg of the 3 legged voltage stabilizer. That leg is what it uses to determine when it is putting out 10 volts. If something is causing that leg to be a couple volts above 0, the output of the stabilizer will be high by that same amount. The usual cause is a weak ground for the cluster. This same issue could make the coolant gauge warning led blink when it shouldn't.

You could tie into the brown wire for the cluster 14 pin connector and ground it to metal nearby. That would only be an answer if the problem is external to the cluster and 14 pin connector. Otherwise you could run a new ground wire from a ground point on the blue foil to body metal nearby. One of the 3 temp gauge nuts is a ground point on the foil.

Mark

[coastdog]

Thanks Mark I will give that a try!

[DanHoug]

the 10v regulator does indeed fail. it is poorly heat-sinked and cooks itself over time. the original part is NLA and while there's a multitude of 10v with the TO-220 form factor, aka the 3 legs, they currently have a different pinout than the original.

sooooo.... a bit of ingenuity is required and our Vanagon vendors all sell one with instructions. or you may buy your own for $0.72 and figure it out. you can improve on the robustness of the install by providing a TO-220 heat sink along with some heat sink compound but that may be overkill.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[coastdog]

Another question-do you know which of the temp gauge nuts on the blue foil is ground and also could I take a jumper from the center leg of the voltage stabilizer straight to ground to test as well?

[Paulbeard]

Necro-post…

I have the converse/reverse of this problem: both this gauges are low/slow to respond. The temp gauge b-a-r-e-l-ly moves off the peg, even as the oil temp gauge is up over 200° (and the heater is good and hot) and the gas gauge will start out honest then slop around between an accurate measure and E. Double-checking the ground seems like a good first step. The dash lights and everything else seems to be fine.

That makes me think the gauges don't share a ground with the lights. Or do they all come through the multiport connector?
_________________
Currently -> Frida: 87 Tizian Red (mostly) Vanagon GL Westfalia w/ 2.0L ABA conversion
Formerly -> Steward of a 73 Super Beetle (Beater) and 67 Beetle 1300 (Little Max) both names by POs

[wcdennis]

coastdog,

The yellow part in your 1st photo is a capacitor, not a resistor. It is associated with the dynamic oil pressure warning system that was part of 86 and up VWs
The part you are pointing to in the Bentley is a 22ohm resistor that is important to the operation of the voltage regulator. the chance that it has failed is slight, but since you continue to have issues, it is probably worth checking. You can find it on the part of the foil that is folded down the middle of the cluster. It is the red-colored resistor (next to the last) in the photo on this page: https://www.thesamba.com/vw/forum/viewtopic.php?t=579342
You can see if it is loose or damaged and make sure it measures 22ohms. Again, probably not the issue but something new to check.