Gas Gauge Failure

geordie · Nov 4, 2011

I'm not electrically gifted. The gas gauge on my recently restored 65 Coupe is reading zero, even though the tank has a good amount of gas in it. It worked briefly then failed. The sender is new, the wiring harness is new, the gauge is original / PO, and worked before the restoration. I'm about to start pulling the dash apart looking for loose connections, but is there anything clever (electrically) I can do to narrow down the source of the problem.

iskwezm · Nov 4, 2011

take the wire off the sender and ground it,that will make the guage swing past full and tell you if its a guage or sender issue

rbohm · Nov 4, 2011

iskwezm said:
take the wire off the sender and ground it,that will make the guage swing past full and tell you if its a guage or sender issue

before you do that though, are any other gauges not working properly? for instance does the temp gauge or the oil pressure gauges read off the charts one way or the other? if so then you might have a bad IVR. if not then proceed with the above suggestion.

geordie · Nov 7, 2011

Thanks rohbm, speedometer is working. What is an IVR?
Thanks to iskwezm, that's exactly the kind of thing I'm looking for.

Capt Dan · Nov 7, 2011

Speedometer is not electric. You can't judge by that.

Constant voltage Regulator

other_shoe · Nov 7, 2011

Comment deleted because Capt. Dan covered it.

rbohm · Nov 7, 2011

geordie said:
Thanks rohbm, speedometer is working. What is an IVR?
Thanks to iskwezm, that's exactly the kind of thing I'm looking for.

IVR=instrument voltage regulator. they often go bad and the gauges will do funny things. for instance when mine was going bad, the oil pressure gauge would suddenly drop to zero, and the temp gauge would spike to its highest reading. after about 15 seconds the readings would return to normal.

geordie · Nov 7, 2011

Capt Dan said:
Speedometer is not electric. You can't judge by that.

Senior moment........

geordie · Nov 9, 2011

OK, took a look tonight.
On the binnacle, the indicator light flashes, the main beam light works, the engine temp gauge is disconnected, I use a separate water temp gauge. I also have a separate oil pressure and voltmeter. I connected the gas tank sender wire to ground......nothing. I then started to remove the binnacle, I got all the screws out but the binnacle does not want to come out, the top seemed free, the bottom was stuck, I did not want to force it. I did manage to get my fingers behind the gas gauge and it seems to have two solid connections. I put the key in the ignition and tried the gas gauge, it read about 3/4 full (which is about right) but then dropped slowly back to zero and would not move any more.
So as earthing the sender did not work, would I be right in thinking that the gauge may be broken?
Any tips on getting the binnacle out?
Where would I find the IVR, on the back of the binnacle?

horseballz · Nov 10, 2011

geordie,
The instrument cluster (binnacle) is being held in by the speedometer cable. you need to reach behind, find the cable and unscrew the outer concentric nut that holds the cable to the rear of he speedometer and then the cable will slip out of the back of the speedometer and then the "binnacle" will be more free to come out a few inches more. The fact that the other gauges have been bypassed/disconnected/replaced with alternate units and that the fuel gauge worked a little and then stopped, points to a likely failed/faulty IVR or bad ground, more likely IVR. Here's a link to a pic to let you see what you are looking for:

10804-1 / REGULATOR

and another:

Results for constant voltage regulator -

The more expensive solid state unit is superior, but the OEM one worked for years, so... your choice!
HTH,
Gene

geordie · Nov 10, 2011

Thanks Gene, so it follows that when I re-attach the binnacle, that I've got to reach behind and re-attach the spedo cable. Is this 'standard operating procedure'?

horseballz · Nov 10, 2011

Yep,
Once the cluster is out, and you see it all, you'll likely be able to feel comfortable enough to give a little tug on the cable to get another inch or so of slack. One good thing is that the speedo cable has been lined up with the speedo for 40-ish years, so lining it back up usually isn't too bad. The nut does not need to be tightened on with a wrench, but getting it cracked loose the first time may be a bit of chore. Once cracked loose, it should spin off with your fingers fairly easy. A tiny wipe of lithium grease on the threads of the speedo may aid reassembly and will certainly assist the next time you take it apart.
HTH,
Gene

geordie · Nov 27, 2011

Thanks guys. I was able to remove the instrument binnacle and replace the IVR. I went for the sold state IVR from Scott Drake. I removed the speedometer cable and also learned that the binnacle has to swing out from the top first. I know have a functioning gas gauge.
Thanks guys, good call.

rbohm · Nov 28, 2011

geordie said:
Thanks guys. I was able to remove the instrument binnacle and replace the IVR. I went for the sold state IVR from Scott Drake. I removed the speedometer cable and also learned that the binnacle has to swing out from the top first. I know have a functioning gas gauge.
Thanks guys, good call.

Gas Gauge Failure

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