Anyone know the correct resistance across the voltmeter on S3? I'm getting 170 ohms on mine. As well, what is the gauge of the insulated wire that is wrapped on the voltmeter action? I'm guessing the wire heats up and causes the metal ribbon the needle is mounted on to bend and move the needle, so is it like a toaster wire?

Just measured 180 ohms on one I had on the shelf, if that helps. Sounds within range.
Bill
Yes. like a toaster element

Thanks Bill. My gauge reads just under 13 volts when the car is running but when I measure the voltage at the lead connectors behind the dash I get almost 14. I was thinking of re-wrapping the metal "armature" but have no idea where to buy the wire or what gauge to look for. It is almost hair like.

Have you tried the adjustment on the back of the gauge itself?

Low reading and very lazy response is typical on these voltmeters

Cheers
DD

My lazy and sticking voltmeter was corrected by "re-bending" the actual needle. It's made of plastic, unlike the other guage needles which I assume are metal are metal. My guess is that it is non-metallic to avoid the magnetic field created by the meters wire coil when supplied with a voltage. Every used meter I've seen has a "bent" needle, which causes it to drag and stick to the backing plate with the voltage markings. Thats why with a dead meter after cold startup's especially, a strong flick of my fingernail would allow it to release and read normally. I opened up the meter and (cruedly) used a cigarette lighter to warm the needle and straightened it and also pulled it up to provide some clearance between it and the backing plate. Worked great for one summer then it promptly "re-shaped" itself to rub again. If I can get my hands on a used, bent needle unit, I'll play around with (ideally) replacing the needle with a non-metallic one, if I can fabricate one. Got a used unit Robert?

Thanks Doug. I saw the shaft sticking out the back and didn't know if that was an adjustment or not and didn't want to over torque it. I'll give it a try.



The needle on my original gauge is as straight as it could be however I "fried" the coil winding when my test leads slipped and shorted out. I bought a second gauge on eBay and the needle was curled like a pigtail, still trying to get a refund on that. Ordered another on eBay and the needle is only slightly bent, can't see if it's dragging. I'll try this one, if it works, fine, if not may try to swap needles but would still like to rewire my original gauge if I could figure out where and what wire to buy. I'm hard headed that way. Thanks for the input.

Is it electro-thermal using a bi-metallic ribbon or is it electro-mechanical that relies on magnetic polarization from coil acting on iron metal ribbon . . . rather like using a magnet to upset a compass?

The coil uses fine insulated copper wire and the resistance you note proves its integrity. If you had burnt it out, it would read 0 ohms. As the voltmeter coil is DC parallel-connected (no shunt as in series-connected ampmeter), perhaps your no-go voltmeter has a different fault. Where and how did you measure the coil resistance?

As for the wire used in toasters, I rely on my yet incomplete PHD in Toaster Technology, which I purchased for AU$5.75 on eBay. LOL. That wire used in toasters is not insulated. It is nichrome and it glows red when subject to sufficient voltage . . . thus, radiating the mysterious "stuff" within this red glow to burn the bread to an acceptable extent. Some prefer warm bread; some go for crispy; few prefer complete incineration! But, I digress . . .

An adjunct to Doug's great advice on manual adjustment is that you can do so while applying a multimeter set to 0-20Vdc in parallel across your voltmeter terminals. Adjust your car's voltmeter to mirror the multimeter reading. Easy peasy!

Cheers and best wishes,

[QUOTE Some prefer warm bread; some go for crispy; few prefer complete incineration! . [/QUOTE]

My late grandmother claimed burnt toast was good for your teeth.
She was brought up on sheep station in the Australian outback.
'Nuf said...............

J, it's called magnet wire, I used to rewire the resistance coil on our simpson multimeters when guys would inevitably check voltage without switching the meter off the resistance scale. I think it was around 38 gauge and I suspect that would probably work for the voltmeter. Amazon...

Cat, I believe it's thermal. The needle is mounted to a strip of thin metal similar to railroad tracks. The wire is wrapped around one of the tracks only and when it heats up the bending torque against the unwrapped track moves the needle. The wire is still intact, hence the resistance reading, but some of the insulation is coming off. I coated the uninsulated parts of the wire using a toothpick and some liquid gasket, adjusted the needle position and now it's more accurate. Adjusting the needle is incredibly difficult, the shaft is tiny and protrudes out of the back of the gauge only a small amount and is hard to turn. I think I've encountered this problem before but can't quite place the situation. 🤔
Thank you for the input. ps, I'm a Thomas English Muffin guy.

Slofut, brilliant! Thank you.

My voltmeter seems to work fine, albeit slow response as are all the others. No bent needle though. My digital solution to instant and precise response was removing the cigarette/cigar lighter and replacing with the below voltmeter. The one BIG added benefit is the USB charging ports for my cell phone or whatever.

Hey, on second thought. If it indeed does heat up enough to flex the card it's wound on you may need resistance wire for winding heaters instead. again very light guage. It's not rocket science and you can diy no problem with a little experimenting.

Now that's worth the trouble!

Oh, okay. Right now it's working better than before so I'll leave it alone. I'm just surmising on how it works as far as heating the metal mounting strip, maybe someone more informed can confirm this or give a correct explanation...........Jack.

Yachtsman, I'll be checking that out. Thanks......Jack.