I can't seem to get the gas gage in my 70 Chall 440RT/Rallye dash to work. I have a new 3/8" sending unit/grounding strap/ wiring to the dash. All the other (oil,temp,ammeter) work. Can you guys give me a sstepby step troubleshooting plan to zero in on the problem? I hate to rip back into the dash as I just got everything all tucked away and neat. Thnx!

With the ignition key on, momentarily ground the sending unit wire, if the gauge responds, it and the wiring are OK. Do not leave it grounded for more than a few seconds or you may damage the gauge.

I did as suggested and with the sending unit wire grounded, the gas gage slowly crept up to full (tank is full). Guess I have a faulty sending unit? Also looking at the wiring on back of gage itself, (rally dash) where is the common jumper wire supposed to terminate? If these are swapped (sending unit and jumper) would gage still work? Thanks, sure will be nice to have a fuel gage again!

If your sure you have continuity between the sending unit & the fuel line several inches away then yes the problem is inside the tank in the sender; open in the windings/saturated float/arm not making contact on the windings/float arm hanging up/stuck. with pulling the sender being such a pain I'd actually run a jumper wire from the sender unit flat metal all the way up to the batt neg post to CONFIRM it ain't a ground issue

OK thanks RR, I'll try that tomorrow

Forgot to mention, my sending unit is an aftermarket 3/8" -- not sure if that has any bearing on this. Never could get to work correctly and have just been living with it. My buddy was saying something about linear vs NON linear with sending unit replacements and they can never work with na stock gage (???)

I just unstalled a "new" aftermarket sender unit and it reads exactly 3/4 tank at full. Now out it has to come again, but how to fix it is the question?

Ive never found a fix, and Im on my third aftermarket sender, all 3/8'. Id happily buy a NOS 3/8' sender just to see if that's the problem, if I could ever find one.

Mine reads 1/2 tank when I have a full tank. It drops very quickly to "E" and will then stay there.

I got my 3/8 off Ebay a few years ago.Its pretty accurate.Its withing Id say 1/8 tank always.The OE gauges werent all that accurate but usually more so than most aftermarkets.You can always try adjusting the float arm to see if its better.Rocky

Who makes your guage Rocky?

Ive tried bending the float arm, in both directions, and its never fixed the problem.

It might get fairly close out of the tank, but once installed in the tank, no matter what its WAY off.

All of you have the same problem! Mopar gas gauge senders have different Ohm readings for full and empty than other brands.

The only senders that will work with a stock gauge are senders with the same range of Ohms. You can bend the float wire all you want, it's not going to make a 0 - 30ohm sender work like a 20 - 50ohm sender. AFAIK there is no generic aftermarket sender that mirrors the Mopar one.

R.

FWIW, the sender should be ~10ohms full and ~80ohms empty. For those that are having problems with the aftermarket senders never reading full or never coming up at all (and the ground is good), try pulling the sender out and cycling the arm (alot) to seat the contact internally. The arm will also move sideways just a little bit. While cycling the arm up/down, try to also move the arm sideways at the pivot point, blow out the assy (there should be a couple small holes in it for that), etc. We've sold quite a few of these and always test them and go thru this routine before we send them out as it's not that uncommon for the resistance to be high without doing this. Hope that helps.