fuel gauge resistor getting hot

mywyld75

mywyld75

Casual User
2 You're 10
Aug 4, 2012
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Newmarket On
VetteCoins
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1975 stingray
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Hi Guys,

Looking for a little help here please

I have finally gotten the car back from paint, and I am now on to the interior. Aside from a few electrical gremlins all is going well.................. until the fuel gauge!

I noticed that it was pinned passed full and managed to get that figured out. Now the issue is that the resistor on the back of the gauge is getting very hot. The wires, connector and mounting studs are cool but the resistor will burn your fingers, I am thinking that this can't be right........... or??????

Can anyone help shed some light on this please.

Pics of the car to follow

Thanks in advance
 
MW75....
That hot resistor does not seem right?
Whenever I have an electrical issue I always look for a bad ground(s) first.
That gauge set-up has a few grounds that need to be checked.
My '75 currently has an issue with the tach, clock and amp gauge...
Come springtime I'm going after the gauge cluster and clean all the grounds.
I suspect these ground issues show up from just having the car sit for some time.
"Everything worked fine when I parked it!"
Good luck...

Graham
 
Not an expert here but from very limited experience, typically a resistor gets too hot from too much current through it and too much voltage drop across it. At some point it will either burn out or catch something on fire. Hopefully someone with more electrical smarts will chime in here for you. Good Luck and sorry couldn't help.
 
Mywyld 75

The resistor on the back of a gauge is used As a shunt or bypass for excess current to protect the gauge . It may not be unusual for this resistor to run hot. Resistors usually have a series of bands on them of various colours to indicate there value. These are read from left to right . If you can give me these colours along with the voltage across the resistor we can calculate the current drain and wattage. The diameter of he resistor is also important as it tells you the wattage of the resistor. 1/4 inch Diameter is a1/2 watt resistor . If smaller in diameter it will be a 1/4 or 1/8 resistor.
With due respect to NASCAR 03 a bad ground would actually increase the resistance in the circuit and cause less current throw the bypass resistor casing it it run cooler.
There would be a warm area around the poor ground.
Does the gas tank have a sender unit that you can access ?
Do you have a service manual on your car?
I will do more research on your when I get home to see if I can help you any more .

Charlie
 
MYWYLD 75,

I have attached a file with the circuit drawing of your gauge and some fault finding ideas.
let me know if you can open this or not . I new to the forum so still trying to figure everything out If you can;t we could do it by direct e-mail.
based on the 160 ohm resister in your circuit @12v you should have a current of .075 amps and .9 watts so it should be cool. The sender unit in your take varies in resistance from 0-93 ohms and possible up to 110 ohms so it would be good to check this as well.
Hope this helps. If you need any hands on help I live about 3 hours away in Belleville.

Charlie
 

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These files open fine Charlie but he will need Adobe reader as they are PDF files. (free download). Thanks. You obviously know what you're talking about on this subject. Love that about this forum. Our members have a broad range of knowledge and experience willingly offer that up whenever asked. Kudos! :thumbs:
 
is the guage reading correct now ? pinned to the end usually means no ground resistance. Are the wires hooked correct at the sender ? , sender ground wire making good contact to the steel ( negative ).
 
Hi guys,

Thanks for the responses and advice. There is a new sending unit in the tank and the connectors can only go on one way as one is spade and the other round.

Is the resistor working harder at full or empty?

The tank is empty and I am wondering if the float is hanging low and at its most resistant point. Would this cause it to "overwork" and heat the resistor???
 
Well crisis averted, the issue was that the float was on empty (or below, no fuel in tank) and the resistor was being overworked. Half a tank of fuel and the resistor is nice and cool.

Just want to say thanks to all for the advice and to Charlie for going the extra mile!

Thanks guys.
 
Like already said and shown in the symptoms posted by my 1999 coupe , if guage shows past full then there is no ground thus the
resistor has nothing to do. In your case the tank is empty, guage shows empty so resistance is high . That resistor on the guage is only suppose to sorta just keep the needle from moving and flopping around quickly like a shock absorber from what I understand. Whatever , glad you got it solved and all is " safe " there.
 
Mywyld75,

Also glad you got this solved .
I was about to send you a new link that had more info on your gauge . You searched for fuel gauge | Willcox Corvette, Inc.
There is the link anyway, as this site seems to have a lot of data on the older corvettes.
My background is 30 years of defense electronics so if you have any electrical issues in the future I may be able to help you.

Charlie
 
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