The gas gauge on my 71 Comet is not working. It worked recently, but now does not. The fuse is good. It is plugged into the gas tank. Not sure what to do now. I took the instrument panel out. I notice that the plastic cover is peeling from the back of the instrument panel, right where the Instrument Voltage Regulator is located. I don't know if this will cause the IVR not to work? I will check the voltage on the plug for the sending unit and see if it is getting power. Suggestions?
Quick way to check a gage and wiring. Have someone sit in the car to watch the gage, key on, and then pull the plug off the sending unit and ground that plug out to the body / frame. The gage should rise to full. If it does, your problem is the sending unit.
The plastic cover is just for protection. If there is no damage to the copper circuit you can glue it back down. I used a small dab of clear flexible adhesive (Plumbers Goop).
Don't ground the wire but long enough to see if that is the problem(half travel is plenty), allowing the gauge stay pinned at full can damage the bi-metal and cause calibration issues... Probably 90% of the time the problem is in the tank...
Most of the time the float rusts and gets a pinhole in it filling it with gas causing it to read empty easy fix you can buy a float on e bay for ten to twelve bucks
Ok, I have not replaced the sending unit in my gas tank with a new one. Now, the fuel gauge is reading above full when I know there is not but 5 gallons in the tank. What is the deal? I guess I can replace the gas gauge. It cannot be anything else, can it?
Yes, it can be as simple as a pinched wire between the tank and the gauge. When the wire goes to ground the gauge goes to full (closed circuit). It could also be a sending unit that is grounding out inside the tank. It could also be a stuck in the full position float. Slide under the car and pop the wire off of the sending unit. If the gauge drops back down to empty - your problem is in the sending unit. If it stays full, start looking to why the gauge circuit is shorted and grounding out.
Let me clarify. I have changed the sending unit. It is brand new. When the key is turned, the gas gauge goes to more than full. When I disconnect the plug from the connector on the sending unit, the gauge goes to empty. What now?
Yes, that helps a lot ......... But you may not like my answer ......... Is it an aftermarket sending unit? I had a similar problem with aftermarket units. Junk right out of the box on more than 1 of them. Found an NOS Autolite on ebay and everything worked fine. I do not think there is anything wrong with your wiring or gauge. Problem still seems to be the sending unit.
I should add - If you can - take the sending unit back out and test it with an ohm meter. That will tell you if it is working correctly or it might be the wrong unit.
It could also be the IVR (Instrument Voltage Regulator). When it goes bad....the gas gauge will go to FULL.
Good point .............. Ron, have to tested the voltage coming down to the sending unit? It will be a pulse, about 2 every second, and be about 5 volts. If you don't have a meter, a 12 volt test probe when hooked to it will pulse and glow on and off, couple times a second.
My name is maveruss1 and I posted a picture of my fuel gauge that always reads 1/4 below Full since I've owned my '70 maverick. Inside the gauge are two adjusting gears. Surprising enough no one has information on calibrating this. So I decided to open it up and see what's inside. Hope this will help you some way. The picture is in my gallery
