Fuel gauge reading full with no gas in tank

[jopizz]

Did you test the sender outside of the tank as I suggested. If it's not working outside the tank then there's no point in putting gas in. It's still not going to read accurately. Running and indicating the correct amount of fuel have nothing to do with each other. They are two different parts of the sender. As for your lights it could be a number of things. It could be the high beam switch on the floor. That would affect the headlights. I would also check the wiring block on the firewall under the brake booster. That is a common point of corrosion. You could be dealing with two separate problems or the headlight switch could be the cause. There is no fuse that only affects the headlights and parking lights. There is an 18 amp circuit breaker that controls the headlights behind the switch. Refer to the fuse diagram in the shop manual or our Technical Resources Library.

John

[johnnystc]

Thanks. I have trouble believing two new tank sensors would be bad. Yep headlight dimmers switch was the issue. Thanks. Will try tank sensor again.

[johnnystc]

Just finished testing the float sensor outside of the tank and it went from full to 1/4 as I adjusted the float. I did ground it in the trunk where the normal ground attaches. So I guess the float/sensor is good and it's a must be a bad ground, right. Really thank you on the headlight issue.

[jopizz]

Your wire plug has a separate ground wire rather than relying on the tank for ground. I agree you seem to have bad ground wire in the harness. I would just run a new ground wire from the sensor ground lug to the trunk. Problem solved. The heavier the ground wire the better your gauges will react.

John

[jopizz]

Really thank you on the headlight issue.

You're welcome. Those dimmer switches are pretty common failure points because of where they are located.

John

[Eric S]

You have a couple of fuses in the light switch.

[johnnystc]

Finally found the problem with the fuel tank sender. After testing in the trunk and it seems to work fine i put it back in the tank and guess, it reads full with no gas in the tank! So it did not make sense after confirming it was fine in the trunk with jumper wires. So I looked at the plug that attaches to the sender. It can only plug in one way. The wires were crossed from the plug and the sender. Ended up cutting the wires, yellow to ground and black to hot. Now reads empty as it should. Whoever makes these senders need to change their wiring. The plug is original equipment on this 1966 Thunderbird!!!!!! I've been trouble shooting this think off and on for months. Appreciate all the helpful posts. Thanks guys.

[jopizz]

There are no fuses in the light switch. It is different from the Squarebird light switch. 1966 Thunderbirds use a circuit breaker and a fuse in the fuse box.

John

[jopizz]

It doesn't surprise me. I would contact the vendor who you purchased it from and let them know so they can contact the manufacturer. That would help others from going through what you went through.

John

[johnnystc]

Thanks I will the last one was from Ecklers, their products have been pretty good but not this.

[johnnystc]

Couple other things I could use some help with. Seems the Temperature gauge is not working at all, I checked the sender on the motor and it looks good. The amp gauge also hardly moves even after letting the car sit several days and cranking the starter awhile. Finally the oil gauge does move but seems very low for an engine that was overhauled right before I bought it and it seems to run good. I thought about replacing the oil pressure sender but not yet.

Next is the transmission. Replaced round seal on filler tube and still leaks after shutting engine off. Fluid backs up into tube with engine off--normal I understand. What can I do to fix??? That little round seal just doesn't seems a good fit. I'm sure other folks have had this problem--any help appreciated.

[jopizz]

The temperature, oil pressure and fuel gauge are controlled by the CVR (constant voltage regulator) behind the dash. That is most likely the problem. I recommend replacing it with a solid state model. Our webmaster Dave Dare can modify your original CVR and make it solid state for less than buying one from one of the vendors. There's not much to the amp gauge. It just works off of the battery. It might be just a bad gauge as long as the wiring is good.

I'm not sure about the seal on the pipe. Maybe someone with a C6 can help you out. I don't think normally that fluid should come up that high into the tube. It sounds like your converter is draining back.

John

[johnnystc]

Thanks, I did replace the CVR a few months ago when I was troubleshooting the gas gauge issue (which is the tank sender missed wired). I think I will check the temperature sender and wiring again to be sure it's good. Also the oil pressure sender since they are all connected thru the CVR I guess. Since the gas gauge is ok now the CVR should be OK I think.

[YellowRose]

John, it has been said by one of our Tbird parts houses that these OEM style CVR units they are stocking these days are having a fairly high failure rate. Considering where they are coming from..... One thing you need to know is to have that CVR unit well grounded for it to work properly. If the gas gauge is indicating correctly, that probably is a good indicator that the CVR unit is okay. It should be sending 0-6v thru the CVR unit to the gauges since they are 6v gauges and NOT 12v ones. As John said, IF it turns out to still be a problem with that CVR unit, considering having Dave ~ simplyconnected take your OEM unit and build a solid state unit, guaranteed for life, in it. He can provide you with the details regarding that.

[jopizz]

I would remove the wires from each of the senders and test with a voltmeter. If you bought a solid state CVR you should see a constant 5 volts on each of the wires. If you bought the old style analog CVR you should see pulsing voltages. Grounding those wires should peg the gauges.

John