The Stovebolt Site Forums The Shop Area The Electrical Bay Fuel Dash Gauge OHMs

The search feature just doesn't work for me on this site it says 'Loading' but never does so pardon me if I'm asking a question that has been asked a hundred times already. I just re-soldered the coil wires on the temp dash gauge which have been broken off for years. For OHMs I am getting 26.4 on bench test and I think the gauge is supposed to be a 30 OHM unit. This is the original 1948 unit by the way. Is this reading within specs or do I need to continue troubleshooting. I'd like to get this figured out before I put it all back in the dash and re-install the fuel tank with a new 30 OHM sending unit. Thank you and thank you again!!

30 ohm full
0 ohm empty

Thank you very much for your info DADS50. I realize I did not make my inquiry very clear. The fuel tank is out of the truck awaiting a new 30 OHM sending unit. Nothing is connected and I am troubleshooting the dash gauge which I pulled and re-soldered before I re-install everything. The dash gauge sitting naked and disconnected on my bench reads 26.4OHMs on my multimeter I think it should read close to 30? Electrical knowledge is my weakness. Maybe I am not bench testing the dash gauge properly or it may need to be replaced. Many thanks DADS50!

Not sure how your metering it or what the readings should be

But I tested a gauge using ohm resisters from radio shack

.. 30 ohm .pic...

Great pic and info DADS50, thank you. This is where I am - I hooked leads from the posts on the gauge to the multi-meter with alligator clips so I had hands free to take a photo. I'm still getting 26.4OHMs readout. Am I testing from the wrong points? Do I need to ground this gauge before testing?
http://s23.photobucket.com/user/littlebuddytoo/media/48Chevy/DSU.jpg.html
Thank you.

I'm not sure about the readings across the post
I believe I have a spare 6 volt in the garage that I know works


I'll get it out tomorrow and meter it as you did


Hopefully someone will chime in who knows for sure.

Uh oh, I erroneously said temperature gauge because that was the gauge I was repairing in a post from yesterday. I got that one fixed so the gauge I am now working on is the FUEL LEVEL dash gauge. Sorry for the confusion, I appreciate your help DADS50!

I just saw your pic. I believe you have missed something. The sending unit is a 30 ohm resistor. The resistance of the gauge is not normally checked. The resistance of the gauge, other than it is not shorted or open, is not important to us. Gauges can be built in a number of different ways. Yours most likely is the two coil type. Not to over think this lets just say it works as two electro magnets.
The Function Test is...with correct voltage and ground attached. The sender post with no connection, the needle will read either M/T or full. With the sender post shorted to ground, the reading will be reversed.
Calibration of gauge is as stated above with resistors. I use a pot (0 to 100 ohms) or variable resistor as a lot of senders are 0 to 90 ohms.

Been sitting back and watching what may come of this thread.
I don't think it matters what the resistance of the meter
movement is, the 30Ω load that Gus has applied to the meter is
an excellent way of checking it in the full position. If you
wanted to check the meter thru the entire range you could
obtain an accurate rheostat so you could vary the
resistance from 0Ω to 30Ω.
http://www.pbase.com/dennygraham/image/159356931

Re-soldering the leads on the back of the meter shouldn't
change the resistance of the coils inside.

dg

Using Denny's diagram you should be able to bench test both the gauge and sending unit, just wire them up to a 6v battery and move the sending unit arm up and down and see if the gauge follows...don't forget to ground the sending unit and gauge.

Battery + to Gauge

Gauge to Sending Unit

Gauge to Ground

Sending Unit to Ground

Mike B

Thanks so much beltfed, DADS50, Denny Graham and Mike B, I now have a lot more information to work with. Sending unit should be here tomorrow, I'll wire everything up on the bench and let you know how the test goes. Thank so much!!!!!

Yes good info

Looks like I won't have to dig out that gauge

Here's a video I made a while back when I tested it
...link...

Like mentioned above. Make sure you ground the gauge and sender.

Great vid DADS50! Thanks. I'll put the gauge back in the dash pot before I test. Many thanks everyone.

Old original gauge - no workie. I connected an aftermarket gauge to the new sender and although the units differed in OHMS, there was activity on that gauge. So, back to the drawing board....replacement dash gauges are expensive and I would like to repair the original gauge if possible. Can anyone point me to a source that shows how to repair a dash fuel gauge? I think the trouble began many, many years ago when a AAA service person jumped the truck with 12 volt. I remember saying to him, "I don't think you should do that, please call out for a 6 volt jump". He said, "Naw, I've done this plenty of times, you just do a quick jump with a 12 volt and it's OK". I dunno, that might have fried the gauge for all I know. Only when I am sure it's complete toast will I spend the money on a replica gauge. Thank you all for your help and guidance!