Fuel gauge goes all over the place. 1970 Dodge Charger

[pnora]

What was your gauge doing if I may ask?

If the temp. and oil pressure work correctly the voltage regulator is not the problem.

 

[sam dupont]

What was your gauge doing if I may ask?

My gas tank readings were dead when I got it and previous experience tells me the insides of the tanks are a nightmare, so that isn't surprising. The Temp worked, then quit, but I did replace the water pump, thermostat, and hoses, so I may not have plugged the sending unit back in. While I have never had a CVR go bad, I will be swapping out the pitted gauges and the replacements probably have a good CVR, but while it is apart, I will replace with new. The next cheapest CVR I found was $100

 

[kiwigtx]

FUEL gauge will litterly show its over half a tank and or 3/4.After a little bit of time it shows way under Empty? Brand new sending unit and I already checked wires. Anybody ever had this happen? Could this be the IVR in dash being out?

Check one more thing if you get an opportunity......

This has happened to me, and probably many others here - the brass float on the sender unit can develop a pin hole from bouncing around inside the tank. If the float takes on fuel, it becomes heavy, and sinks. Sometimes it will be full of fuel and move about the tank while the car is in motion. This will give fluctuating readings on the gauge.
The only way to check this is to remove the fuel, drain the tank enough to remove the sender unit, and it will become obvious immediately what the problem is.

 

[PurpleVcode]

I have learned a little about CVRs recently with my Scout 800. I have to admit I didn't check the sending unit plug to my temp gauge and the tanks haven't been used in 30 years, but I found a nearly non-existent CVR for only $33 delivered, so I bought it. I'll change it out regardless as when they go bad it can be bad.


View attachment 1584840

Here's a solid state alternative: RTE limiter - rte

 

[sam dupont]

Here's a solid state alternative: RTE limiter - rte

I read about those, but with my limitations in electronics, I understood them to be a steady 5 volts. The CVR fluctuates with a voltage that hovers in the 5 volt area, but not exactly. Some people get weird or inconsistent readings with electronic, so I found vintage OEM.

 

[Dominic Torreto]

If the temp. and oil pressure work correctly the voltage regulator is not the problem.

They dont

 

[Dominic Torreto]

My gas tank readings were dead when I got it and previous experience tells me the insides of the tanks are a nightmare, so that isn't surprising. The Temp worked, then quit, but I did replace the water pump, thermostat, and hoses, so I may not have plugged the sending unit back in. While I have never had a CVR go bad, I will be swapping out the pitted gauges and the replacements probably have a good CVR, but while it is apart, I will replace with new. The next cheapest CVR I found was $100

I still have my old sending unit. This one I put on 2023 less than 10 miles on unit. I can plug my old one in and test that theory though.

 

[440beep]

My 69 Bee with Ralleye dash had the same fuel gauge issue even with the extra 10 gauge ground wire from sending unit to frame. Sending unit is a Spectre, made in Mexico unit. Only after I pulled the instrument panel and cleaned the gauge circuit board etchings with a brass wire brush and retightened the gauge lock nuts does the fuel gauge finally read properly.

So maybe the instrument panel needs pulling and the etchings cleaned up and lock nuts retightened.

 

[kiwigtx]

My 69 Bee with Ralleye dash had the same fuel gauge issue even with the extra 10 gauge ground wire from sending unit to frame. Sending unit is a Spectre, made in Mexico unit. Only after I pulled the instrument panel and cleaned the gauge circuit board etchings with a brass wire brush and retightened the gauge lock nuts does the fuel gauge finally read properly.

Nice work Lee.

 

[440beep]

Thanks mate! After having the Bee for 12 years, that’s been the biggest highlight of having her, oh, and getting the dash lights in the right sockets now so the dash is finally very bright.

Nice work Lee.

 

[Dominic Torreto]

Changed the cvr still doesnt work and when you ground it doesnt go to full. This gauge has to be bad guys. Its like nobody has ever had a bad fuel gauge befoee.

 

[pnora]

Changed the cvr still doesnt work and when you ground it doesnt go to full. This gauge has to be bad guys. Its like nobody has ever had a bad fuel gauge befoee.

Sure. Just need to logically diagnose it so you do not waste your money on parts that wont fix the problem.

 

[dadsbee]

^^^ exactly. It's not like the gauge is cooked and not working at all. Get yourself a 10 ohm resistor, tear the cluster face off and then feed the gauges sender input through that resistor and adjust the gauge mechanism to read full ! Then put it all back together...