On my son's '71 142, the needle on both the temp gauge and the fuel gauge move to the far right as soon as the key is on. Does someone know what the problem is and how it's to be fixed?

Thanks in advance.

JIm Hampton

If I was in the US I would build you a voltage regulator and mail it. But any electronics hobbiest would be able to do it for you. I've done it a few times for a family member's Chev V8 truck (he damaged the first one, and when he sold the car I built him a new one plus spare). It is about $10 or less in off-the-shelve components. The big question is just at what voltage you want it. I recall 10V being correct, but the Chev was 5V. But that was much newer aftermarket gauges.

The voltage stabilizer (in general, I'm not refering specificly to the Volvo implementation) works as the first reply stated, execpt that after a while the switch closes again as the bimetal cools down. It opens and closes about every second or two or three or something. On average over a period of time you get 5V or 10V (depending on design) to the gauges, but this is switched 12V/0V with some duty cycle in order to get the designed average voltage. And the 12V is to give a quicker response. In fact, if you watch closely, you will see the gauge moving fast, then slow, then fast, then slow. I can especially see this on my 240.

A regulator would always supply the designed voltage, a stabilizer gives on average the designed voltage. Since this thing switches between 12V and 0V it is called a stabilizer and not a regulator, but it does virtually the same job. Modern light weight high power power supplies like in your computer use a switching regulator, which is just an electronic version of the voltage stabilizer but switches at a much faster rate. About 100 000 times per second. The advantage is that you do not have a voltage drop across your regulator, and we all know that power (and thus heat) = voltage x current. No voltage drop means no heat generated means longer lasting.

Have fun...

The infamous 'voltage stabilizer' or whatever the proper term is.

DON'T USE THE CAR UNTIL YOU FIX THIS OR YOU WILL FRY BOTH GAUGES!!!

The gauges are designed to run on 8 or 9 volts (not sure of the actual value) which is provided by a resistor gadget on the back of the instrument panel (looks like a small silver relay). An additional 'feature' of that gadget is that it provides a brief shot of straight 12 volt current when the key is first turned on to make the gauges jump up all lively, instead of languidly creeping up to their readings. After a second of 12 volt, little wires wrapping a bimetallic strip inside warm it up and break the 12 volts so they get 8 volts, ensuring that the gas gauge in particular is too sluggish to react to all the sloshes in the tanks like the nervous twitchy earlier gauges did.

And, after 5 - 10 - 15 - 20 - N years the little warming wires break and suddenly the gauges just get continuous 12 volts, which will in fairly short order overheat their innards and render them inoperative. As a really quick fix you might try unhooking the temp and gas sender wires on the engine and tank, preserving the gauges until you have a chance to pull the instrument panel and remove the voltage stabilizer. Then you have to track down one that works. Can't say how hard that is now. I think I recall Ron Kwas (SWEM Swedish Embassy) talking about making a modern replacement, but I don't know if he did.
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I'm JohnMc, and I approved this message.

I've read rumors that vw bugs used a similar gadget. There are more
bugs out there than bricks, these days.

"There are more bugs out there than bricks, these days."
Triumph of quantity over quality.
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I'm JohnMc, and I approved this message.

Thanks a lot.

I'll disconnect stuff. The car's not needed right at the moment anyway.

Jim Hampton

I have a similar problem with my Volvo 144S

Among a large slur of electrical problems, the gas and fuel gauge do not work properly. before i replaced the coolant temperature sensor, the temperature gauge would sometimes rise up about a centimeter out of the left corner before dropping back down again. this would happen at random times, when i had just started it, or after running for a while. then i replaced the sensor because my dad said it was probably that more than anything. well, it didn't change anything, it still does the same thing. BTW: i read that the gauges run on 10v, not 8 or 9.
the gas gauge doesn't work at all, i am not even sure it has a needle haha. The guy who i bought the car from; his son hit a rock the size of a small basket-ball with the car :(, smashing a hole in the gas tank in the process. it was since then "fixed" but i don't trust the job that whoever fixed it did. anyway, would that kind of accident knock out the sender, or is it the voltage regulator? i don't think its still the stock regulator because it was taped with electrical tape to one of the plastic-wrapped bundle of wires in the wiring harness under the dash. I found a round relay drifing around in the wiring under there, it is about an inch or so in diameter and two or so inches long. it has two male prongs opposing one another at one end, and another male prong off to the side of those that looks like it had some bad little electrical explosion inside of the reley-if thats even what it is. actually, now, just looking at it, it says '12v' on the side, so it can't be the voltage regulator. wow. anyway, i am pretty familiar with the car's innards, as i bought it for $200, and most everything happens to be worn out.

Any help would be greatly apreciated; i will post the other problems with the car in a different thread, i put this one here because it was a similar problem.

thanks a bunch,

Ben
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btw, even though vw bugs are pretty cheaply built, you have to admit, they are pretty cool little cars. i still prefer my cast-iron B20B to vw's little aluminum engine, tho. :)