Couple gauges not working
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Freshman User
Joined: Aug 2015
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Couple gauges not working
So I just bought a 77 f250 and the temp and fuel gauge are not working. If I ground them they both make a full swing. So fuel tank works when grounded only at the dash and at the fuel selector switch. I haven't had any luck by grounding at the tank. Now looking at the selector switch I have a green and green with red stripe that come from the tanks should I be getting any voltage from these wires? When I check it, it's a solid 9.2 volts for a second then fluctuates randomly. If I check for voltage at the tank it's under a volt. I assume this is my issue but any input would be appreciated.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
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Temp gauge sounds like the sender. You grounded the wire where it connects to the sender?
Senders can go bad, and they can be installed wrong - with teflon tape, which keeps the sender from grounding to the engine. It could also be the wrong sender, as for whatever reason, it might have one for a warning light, which is different from ones for gauges.
Unable to help with tank wiring, but hopefully when you get it working, you'll find the floats and senders working properly.
Senders can go bad, and they can be installed wrong - with teflon tape, which keeps the sender from grounding to the engine. It could also be the wrong sender, as for whatever reason, it might have one for a warning light, which is different from ones for gauges.
Unable to help with tank wiring, but hopefully when you get it working, you'll find the floats and senders working properly.
Elder User
Joined: Jan 2014
Posts: 898
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From: Chillicothe, IA
The fuel selector works from resistance from the ground side, so no power should be measured. I am guessing you are not using an $800 fluke meter, so, fluctuations from a meter not actually reading anything is common. At the senders on the tanks, there are 2 wires. one goes to a chassis ground ,the other goes to selector switch. If you ground out the wire at the sending unit, and it doesn't move the gauge, most likely you have either bad wiring or a bad selector switch.
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Freshman User
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I was finally able to get it to register a reading at the tank I originally went at the rust with a wire brush and today I whipped out the grinder and went to town. With some tinkering I was about to get a reading. It must be super sensitive. I guess I'm going to upgrade all the body/frame grounds and battery cables and replace the plug going to the tank. A quick picture as a thanks for the help!
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Freshman User
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The fuel selector works from resistance from the ground side, so no power should be measured. I am guessing you are not using an $800 fluke meter, so, fluctuations from a meter not actually reading anything is common. At the senders on the tanks, there are 2 wires. one goes to a chassis ground ,the other goes to selector switch. If you ground out the wire at the sending unit, and it doesn't move the gauge, most likely you have either bad wiring or a bad selector switch.
Elder User
Joined: Jan 2014
Posts: 898
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From: Chillicothe, IA
Pull it out and move it. It will probably need some cleaning, but be gentle, as i am not sure you can replace the one for the mid ship tank. This is the tank closest to the cab. I am curious, since you said you hadn't gotten your new front tank. I am assuming you mean mid ship, which to my knowledge no-one makes a replacement for.
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Freshman User
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Pull it out and move it. It will probably need some cleaning, but be gentle, as i am not sure you can replace the one for the mid ship tank. This is the tank closest to the cab. I am curious, since you said you hadn't gotten your new front tank. I am assuming you mean mid ship, which to my knowledge no-one makes a replacement for.
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Cargo Master
Joined: Nov 2011
Posts: 3,354
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From: Great American SouthWest
Common for the fuel selector valves to go bad. I think they get gummed-up inside, and there's not really any way to disassemble them for cleaning.
When they are good, you can hear (and feel) the solenoid click when you (or a helper) hit the switch.
Unfortunately, new ones are 5/16 and the original is 3/8
When they are good, you can hear (and feel) the solenoid click when you (or a helper) hit the switch.
Unfortunately, new ones are 5/16 and the original is 3/8
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Just a little update. I could not get the rear fuel tank off thanks to someone welding a hitch receiver to the frame and welded a cross member to the frame rails under the tank. So I had to remove the bed and the bolts had to be cut off. Used a grinder cut the bolts picked the bed up with a floor jack just enough to get the old sending unit out and the new one in. New seal was too big for the groove in the tank, cleaned and reused the old seal. Put back together and filled it up so far no leaks and I FINALLY have a working fuel gauge. The mid-ship tank is on back order from bronco graveyard they said it'll be in stock in 1-2 weeks and be shipped out right away. I'll report back if that does ever show up. If they can't deliver I am going to try and do a repair on the original tank as it appears to only be leaking from the seam. Thanks papabearyuma, 4x4slik, meangreen92 for your help!
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