[B]I allowed the name Airstream Land Yacht to turn my head. I foolishly bought a bus in major TLC. The people who installed my rebuilt engine did something to mess up the gas gauge?? They claimed to install a new fuel pump with is also part Gas Gauge Sending Unit. My dash gas gauge now reads full all the time. How do I troubleshoot the gas gauge problem. Tnanks, Lonnie Stepp

I have no idea what chassis, engine, or tank configuration you have. (Did you try an Airstream forum?) More information makes it easier to answer. I will give the generic answer best I can.

Since the gauge is moving, it probably has power to the gauge. From there the wire goes to the tank selector switch (if you have dual tanks) then back to the tank. The wire then goes to the fuel sender inside the tank.

The tank float arm is attached to a sliding resistor (like a volume control knob) As the float moves, the resistance to ground changes and the voltage of the wire changes. This is what the gauge is actually measuring.



There are a couple of possibilities to consider.

Check the wire connector from the coach to the top of the tank, this connector is often corroded. Be sure there is a good connection there. Assuming there is no problem there, I would disconnect the plug, use a voltmeter to check for power when key is on.

On GM chassis there are 3 wires: power to fuel pump (tan wire) sender wire (pink) and ground (black). The pump and gauge share the same ground wire. If the pump is working the ground connection is probably OK.

You should have 12 volts on the sender wire when disconnected. If you then ground the sender wire you should see the gauge move. If not, you have a wiring problem.

If the gauge changes then the problem is in the tank sender. The float arm may have been jammed and stuck when installed, or perhaps bent or damaged the sliding resistor. You will have to remove the sender to check these.

Hope this helps, good luck.

Thanks. The bus is a P32 Series? Chevy with a 454. The gas gauge remains on full. Before the people who have a gaint Ad on TV broke my personnel door entrance interior door handle. Etc, etc. Anyway, I refuse to take my RV or my wallet back to be abused. The gas gauge sets on full and does not move. Why does the gauge remain on full? Lonnie

The sender uses the ground to indicate tank level with resistance varying with tank level. Your issue indicates the circuit is stuck on "full"; I suggest checking the ground wire for a short.

I had the same problem. The lead on the sending unit had a rivet with corrosion around it. I drilled out the rivet, cleaned with sand paper, applied some dielectric grease, and re-attached the lead with a brass screw.

As Ed suggests, the problem is more likely an open circuit/ poor connection than a short. A short to ground will show empty on the gauge, an open ground or open circuit would not allow the fuel pump to operate. This points to the connection Ed mentioned. (See where the pink wire attaches to the sender)

Just keep the tank full and the gauge will be right!... Sorry... Couldn't resist...I think the gauge reads full if it has power and ground through case or separate ground wire... The wire from the sender to the gauge runs through a variable resistor (pot) in the tank to ground to change gauge reading.... Sometimes the pot goes bad (wears out the resistive under the wiper )... I have bent the wiper on many pots to an unued part of the resistive part... Or an 'open' ( not a complete connection.. IE..broken wire, bad connection between wire and connector... Tug on it)... A volt meter helps but only if you know how to use it ..a helper to watch the gauge while you jiggle wires is great help...sooty you don't have a barth yet... But an airstream is ok start ....good luck .. Or just keep that tank full....

'92 30' Breakaway..

It depends on the sensor; the sender in the gaso tank for my genset shows full when the wire is grounded.

However, both an open and a short need to be investigated.

Will I have to drop the gas tank to access the pink wire?
My son was kind enough to drop the tank on my 1998 GMC 1/2 ton pickup and replaced its full pump. The wires are locked into place on my GMC's fuel pump & float.
He cold burnt his hand repair an Air Conditioner; now it will be left up to little or me. Thanks Lonnie Stepp

Yep ... Could be either way .... Haven't had mine not work so not sure which way it is ... Might look at mine when I'm bored...or/and out of beer

If all I had was a piece of wire,like McGuire, I would disconnect the wire from the sender at the gauge and see if the gauge goes up or not... Take the McGuire wire and connect the gauge terminal, where the wire from the sender went. to a ground and see what the gauge reads... that should tell you whether the wire from the sending unit is open or shorted...If you can get to the sender wire from the tank area, disconnect it there , reconnect it at the gauge and open or short the wire to ga ground at tank end and see if the results are the same as before... I'll check my schematics and stick a meter on mine tomorrow and post back what mine is like...

Thanks guys I hope your information does the trick.

At the gauge, check for 12 volt input first. Then check for a good ground. Connecting the signal terminal to ground should read empty, and 90 ohms resistance should should read full.

If the gauge test is good, then check the wire at the sending unit to be sure it is tight and corrosion-free. It should have almost 0 ohms from one end to the other. Make sure the body of the sending unit is well-grounded to the frame. If that doesn't work, remove the sending unit and check inside. I found a bad connection inside my sender.

I found poor internal electrical connections in the fuel level sender. One, in particular, was an example of very poor design...........a brass tab riveted on top of the aluminum mounting plate. Brass and aluminum in the presence of road spray and atmospheric moisture is very, very dumb. There was another internal connection of aluminum to aluminum that had just begun to fail, as well. I had to use a megger to check it properly, but it was starting to go. I just made an end run around them by running a jumper to a new screw that went from the jumper through the top plate up to where it became the new connection for the ground circuit. The other end of the ground circuit, where it is connected to the frame, also got a good cleanup and a new terminal. And, of course, the external connections get a shot of LPS-3 at the end.

The sending unit is a Medallion B-1321 90 ohm unit, very common in hot rods and boats. West Marine number is http://www.westmarine.com/buy/...ts--P006_180_003_536 It also mates with the OEM Chevy gauge.

I had a sending unit gasket in stock from my boat parts stash. It is a Delco 1516395 or VDO 226-053. Jeg's carries it. http://www.jegs.com/i/VDO/918/226-053/10002/-1 West Marine
http://www.westmarine.com/buy/...hole-gasket--8979106 has it. It is their number 8979106 and Moeller # 35728-10. Old GM vehicles also used that gasket until they went to the twist lock fitting on top of the tank. NAPA has a similar gasket on their site under the number BK 7012378 http://www.napaonline.com/Cata...K_7012378_0361188548 but good luck at the counter. The parts professionals were unable to convert the Delco number or even find the NAPA number that is on their site. It is a standard SAE design.

Titeseal is a good gasoline-proof sealant for this. Or Hylomar or black in a tube Permatex.

Thans guys, you are truly lifesavers