Packard Forum Index » Post-War (1946-54)

Hi all; my buddy has brought me a few fuel gauges 1952 or 53. He has asked me if I could test them out of the car. I have a good sending unit with the correct ohm readings for these gauges. My question is?. Do I run these fuel gauges on straight 6v? Or is some voltage reduction needed. If voltage reduction should be done, what could I use?.
Dave O.

The gauges run on a nominal 5v so you either need the stock instrument voltage regulator or some have managed to replace the regulator with an inexpensive 12 volt input to 5v out power supply available from Amazon or ebay. I don't know personally how well that works but worth a shot if you don't have a regulator. The one I linked to should work 1 gauge satisfactorily for testing. If you use the stock voltage regulator, in additon to the power in terminal and the output terminal, be sure to ground the case or it will not work properly. Depending on the supply voltage, a non working regulator could damage the gauges.

There is an article on testing the gauges in the Dec 1950 issue of the Service Counselorhttps://packardinfo.com/xoops/html/downloads/SC/SC-VOL24NO12.pdf but the two sender resistance values you need for 51-56 gauges are 70-75 ohms at empty and around 10 at full.

If you're bench testing, you should use a variable power supply/calibrator and not a battery.
A car battery has way too much amperage for this. If the only way you have for power, then use a lead with an in-line 1-3 A fuse max. I'd use a disconnect also.
Otherwise, if it's not correct and shorts you'll light things up at full battery amps.
I think I paid ~$80 of a digital PS that can do up to 4 A. Constant voltage or amperage selectable. Comes in handy for testing. And don't have to lug a big heavy battery around. They make portable calibrators with rechargeable battery units also but more expensive.
You'll need a DVM also.

Thanks so much for the info. I did check into the Amazon unit. 12v to 5v 3amps. I'm sure my buddy would spring for that. Another unit was suggested for my post, but the price would not be justafiable for a one time testing. I though it would nice to own one.

Thanks again.

If you can find an instrument technician they can probably do.
You'll have to be aware of the "ground" and how you set them up to get the right values since I think they're one wire.

I haven't done any calibrations for about 25 years now. I was called out in the night during winter and did one in the field off a ladder with steam condensate dripping on me. It does sharpen you're focus and speed of task. So I'm not found of that task. Arse chewing is retroactive and loses impact.