C2 temperature and fuel indicator

[Joep F.]

Dear All,

I have a problem with the following indicators:

1. The temperature indicator does not indicate any temperature. Replacing the sensort did not help.

2. The Fuel indicator does not show more then a half full tank. When its getting less it works. When the tank is more then half full it doesnt show more then half.

Anybody can advise?

Thanks,
Joep

[Rob M.]

Re: C2 temperature and fuel indicator

Joep,

First of all welcome at the NCRS tech. board!

Question 1)
You should measure using a multi-meter if you have any voltage between the wire which normally is hooked up to the temp. sender unit and the ground if you have any voltage. If not it is likely the fuel guage is either burned out or it is not properly hooked up to the harnesses involved.

Did you check all your fuses? Also this can be done by measuring the resistance of each fuse (even while they are still attached in the fusebox).

Question 2)
It sounds like the handle with the float doesn't have a free travel or is jammed half way. Have you chech the float by removing it from the tank (after emptying it first)? Otherwise I recon the variable resistor in your sender unit is partly broken. This you can test when you've got the unit unmounted from the tank by measuring its resistance. This should gradely increase while you move the handle with the floaf from 0 to max. range. When it stops increasing half way or is still 0 half way then it is broken and you'll probably have to replace the unit.

PS Picture is showing C1 sender unit but for C2 it should be similar...

greetings,
Rob.

[Jack H.]

Add on...

I agree with Rob on his advice about diagnosing the temp sender, but I disagree with him on the fuel gauge.

The fuel gauge system used in '63-67 cars is unique. It's based on a Whetstone bridge circuit topology, which was done to make gauge readings independent of absolute battery voltage (is the battery being charged or not and how strongly is it being charged?).

As a result, GM had to teach service mechanics how to troubleshoot this 'new fangled' system and complete schematics + a table of diagnostics based on observed symptom were published in the 1963 Corvette Shop manual. Here's what you'll find if your crack your copy of the book:

Symptom/Proceedure

Pointer does not read above 1/2 position/Tank guage unit is not grounded.

Pointer is stuck at 1/2 position/Poor connection of terminals in brown wire or physical break in brown wire.

[Don 42616]

Re: C2 temperature and fuel indicator

My C2 gage would not read more then 1/2 way. I put my hand in tank filler & bent float untill it showed full with full tank. Works fine. (except my hand)

[Gerard F.]

Re: C2 temperature and fuel indicator

Don,

Better off just using a wire coat hanger. Move the float up and down until it works.

Jerry Fuccillo

[Don 42616]

Re: C2 temperature and fuel indicator

Gerry, Problem was I HAD TO BEND IT upward (like a toilet float). I hated to put my hand into tank as I also use Lead additive !! It reads right on. I probably shortened my life. But it is worth it!! There was not enough room for gloves. Don

[Gerard F.]

Re: C2 temperature and fuel indicator

Don,

Heh, heh, heh! I don't know if you heard my story about the time I was trying to adjust the terminal nuts on my fuel sender from the underside. It was a repro sender which I found out, just has a pressure fit, no terminal nuts.

All of a sudden drip, drip, drip in my face. Luckily, I only had 6 gallons in the tank, a siphon hose handy and a 5 and 2 gallon gas can. In my haste, I almost took a swig of the stuff.

That's why my original sender is back on the 67.

Jerry Fuccillo
#42179