Temp sending unit
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Joined: Dec 2009
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From: Alvin, Texas 77511
Temp sending unit
I have a 239ci in a F1 Ford Truck and the gas sending unit I guess has gone out or quit working. The guage shows full all the time even though the tank is half empty. The truck is 12 volt but I have reducers on the guages so I need to know if I should purchase a 12 volt sending unit or should it be a 6 volt one. Tomorrow I'm going to check the unit out to see if maybe it is just stuck in the full position. Does anyone know what the amps or voltage should be at the tank. First time I have had trouble with this so any information would be thankfull.
Thanks for any responce,
Larry Brauer
Thanks for any responce,
Larry Brauer
Fleet Mechanic
Joined: Sep 2010
Posts: 1,829
Likes: 466
From: Mason City, Iowa
What I would try to do is to isolate and test the gauge. With the key in run, does the gauge return to "E" if you pull the connection off the top of the tank? Then, if you short the gauge wire to ground, (away from the tank prefably) the gauge should read "F". If the gauge tracks the way described, then the gauge is OK, but the sending unit is bad. I.M.O. If you do come up with a bad sending unit, and you are using 12v system, but 6v for the gauges, then I would continue with the 6v sender. About a year ago, I kind of had the opposite problem with mine. It would read "E" all the time. I verified the gauge itself was good by grounding the sender connection. Then I pulled the sender and found the problem...the float had drowned because of pin holes! A new float and everything was back to normal. In your case the float arm could be stuck, or the reostat inside the unit (which controls the amount of current flowing through the gauge to ground) may of shorted. I hope this helps! One thing about these trucks, I don't know what I enjoy more, working on them or driving them!
Fleet Mechanic
Joined: Sep 2010
Posts: 1,829
Likes: 466
From: Mason City, Iowa
Larry,
One other thing, there could also be an undesired short to ground on the wire between the gauge and the tank. If, you disconnect the sender at the tank, and you still see "F" at the gauge, but with the sender wire still disconnected, the gauge goes to "E" after shutting off the key...then something is probably shorting the sender wire back to the instrument panel. Could be a tip of a metal screw, worn wire against a sharp metal corner etc. If it's that, you might just be farther ahead just running a new piece of wire between the gauge and the tank's sender. And then start saving up for a new wiring harness!
One other thing, there could also be an undesired short to ground on the wire between the gauge and the tank. If, you disconnect the sender at the tank, and you still see "F" at the gauge, but with the sender wire still disconnected, the gauge goes to "E" after shutting off the key...then something is probably shorting the sender wire back to the instrument panel. Could be a tip of a metal screw, worn wire against a sharp metal corner etc. If it's that, you might just be farther ahead just running a new piece of wire between the gauge and the tank's sender. And then start saving up for a new wiring harness!
