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MichaelDGod · 08-23-2016, 09:27 PM

So my Fiancee and I just purchased these beautiful Class A motor home and there's a few pieces here and there that need fixed one is the gas gauge. For some reason it reads empty no matter how much gas I've put into it.. can anyone help me out admin please move if wrong thread...really don't wanna drop my tank...

ahicks · 08-24-2016, 09:37 AM

If you know which wire it is back at the tank, you could cut the wire in a reasonably accessible place just ahead of the tank. To check gauge at that point, and the wiring from gauge to where you cut the wire, you can expect gauge to read one extreme with the wire grounded, the other extreme with the wire disconnected. (way full or way empty, can never remember which is which). Whatever, if the gauge moves from one extreme to the other (grounded vs. open), the gauge and the wiring leading to the tank (or wherever you make the cut) is good. At that point it's time to get serious about dropping the tank.

Don't assume it's a bad sending unit. Often as not, it will be about the ground wire from the sending unit to the chassis.

MichaelDGod · 08-24-2016, 10:15 PM

So I forgot to mention it is a dual tank and both are reading empty...no way two sending units went out back to back right lol?

ahicks · 08-25-2016, 06:34 AM

Pretty easy to test. I'd pull the switch for easy access. Identify the wire leading to the gauge, and test it as suggested above. Should take maybe 5 minutes?

F76Marion · 08-25-2016, 12:05 PM

Michael,

Before you do anything else, get a test light and get close to the fuel tank. This symptom is typical of a bad fuel tank ground.
Get a good (make sure it is good) ground near the tank and try to connect to the tank. Do you get a flash??

The old Mopar stuff had thermal gauges. So, they used a thermal regulator. while crude, they are anvil reliable. They regulate the voltage by pulse width.

No flash there? Then check the sending unit resistance at the back of the IP. It should be a small number. (The actual value has slipped my memory), but if is over 100, the sending unit is probably gone bad.

The sending unit in anything older than about 1980 can be attacked by the alcohol in current "motor fuel". Repair is pointless as it is a material incompatibility issue.

Frank