The Stovebolt Site Forums The Shop Area The Electrical Bay fuel gauge reads half full with full tank?

I'm sure someone has had this problem before. I've done some searches but just wanted to see if anyone had the same problem. I haven't checked the sender with an ohmmeter but I have two sending units that have checked and both give me the same reading. As I move the lever arm of the unit the gauge stops at half full when it should say full. I sent the gauge off to D and D instruments and they said it checked out OK. So it seems I have two good sending units and a good gauge. The truck is a 6 volt '53 3100. I don't think the sending unit is volt specific and the gauge is an original unit. What next? Could my ground be weak? Help...anyone?

First thing to do here is to check the guage as it's mounted in the dash: Disconnect the sender wire that goes to the guage at the sender unit. Turn on the key, the guage should read FULL.
Then, ground the sender wire to a good ground, the guage should read EMPTY. If the guage does not read as noted above either the guage is bad or it is not properly grounded to the dash.

If the guage is good, you prolly have a 90 ohm sender in there instead of a 30. You can check the resistance with your ohmmeter.

Could the needle be bent? Ive done all the same tests with mine and Ive concluded that at some point I must have bent my needle installing it or removing it. I never worry about it though, when my tank reads empty Ive still got about 3-4 gallons in it!

I'll try all those test tomorrow and let you know what I find out. I know the needle isn't bent because the gauge will read up to full when I disconnect the ground.

Did D&D know you had it in a 53 6v system?

The senders/gauges worked together on two different ohm limits (90 ohm or 30 ohm, I think).

Maybe atomarc will jump in on this one.

Tim,

I sure don't have much to add other than making sure the gauge is grounded properly in the dash cluster.

Stuart

The gauge should darn near bury the needle when you pull the wire off, along with grounding it and burying it in the other direction. Its been awhile since I messed with mine, but I believe the gauge should peg past full when you disconnect the wire. Just a thought.

Jeff

graydon,

"I know the needle isn't bent because the gauge will read up to full when I disconnect the ground."

Are you referring to the sender lead? If not, what ground are you disconnecting?

rustednuts' comment above is right on the mark - that is a good test to see if the gauge itself is good.

Tim

If it worked ok before and then just started reading half full with a full tank, the most common problem is a pin hole in the float that makes it start to sink in the tank. If it started after installing new items, I would backtrack at that point. In my thought process, if you can pull the tank sending unit wire and the guage goes to full, I think voltage is sufficient to get it to full when tank is full.

OK I've done some testing. When I pull the sending unit wire from the sending unit with ground still attached the gauge goes to full. It also goes to full when the sending unit is attached and the ground is removed from the sending unit. If I remove the sending unit wire at the sending unit and ground it the gauge will drop back to empty. I have full range of motion in the gauge and it seems to be working properly based on tests above. If all wires are connected and I move the lever on the sending unit to its max it still only reads half full. I'm going to check all the grounds to make sure they are good. How exactly do you check the Ohms/resistance? ie. which lead to where? Sending unit to a good ground?

Thanks

you need an ohmeter, one lead on the connection peg, one on the sender frame [no "polarity" involved] - move the float arm and you should read 0 - 30 ohms

Bill

It is possible to get the teeth on the float arm gear out of sync. My rivet that held the float arm to the sending unit was loose enough that when I had it out it had enough wobble to let the gears slip. I had to re-calibrate it before I put it back in with an ohm meter. If you had your unit out of the tank check this.

OK, I got an ohmmeter and both the sending units tested good with a resistance of 30 Ohms. I had the gauge checked and all was good. Could a poor ground be the cause? I'll check into and let ya'll know. Otherwise, anyone else got any ideas?

Thanks for everyone's help.