Temp Gauge help
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Joined: Nov 2010
Posts: 77
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From: Richmond Kentucky
Temp Gauge help
1976 I put in a new gauge new sending unit still don't work ! If I ground the green wire it goes to about 3/4 of the way to the right not quite to the red . The resistor on the back of the gague reads 91.5 ohms . I am thinking the gague is not calibrated correctly . Any help ?
Safety Car
Joined: Aug 2001
Posts: 4,883
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From: North Easton Mass
Roger or Willcox will probably chime in on this, but one thing you could check is that you are getting 12 volts on the wire with the ignition turned on. Unplugged from the sensor.
Rick B.
Rick B.
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
This is something I need to test but I think that this will respond just like the fuel gauge... On a fuel gauge if the resistor is bad or not making good contact it will only read 1/4 tank max... at full ohms.
Tomorrow, I'll test up a temp gauge to see if I'm right.
I like knowing this and other gauge readings, it helps Id the problem faster.
Tomorrow, I'll test up a temp gauge to see if I'm right.
I like knowing this and other gauge readings, it helps Id the problem faster.
Last edited by Willcox Corvette; Aug 15, 2011 at 10:30 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Ok.. tested today..
A temp gauge that has a broken or missing resistor with everything else hooked up properly will peg about 1/8" past the right hand face rivet.
A temp gauge that has a grounded out ohms wire with everything else hooked up fine will peg about 1/8" before the right hand face rivet.
I've got pictures
I'll add these to the web site soon.
Willlcox
A temp gauge that has a broken or missing resistor with everything else hooked up properly will peg about 1/8" past the right hand face rivet.
A temp gauge that has a grounded out ohms wire with everything else hooked up fine will peg about 1/8" before the right hand face rivet.
I've got pictures
I'll add these to the web site soon. Willlcox
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Race Director
Joined: May 2006
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From: Dayton, Ohio
OK Ernie I'm going to have to go back to the drawing board,my notes say 1 oclock without the resistor and the sender wire grounded. 
All my testing gauges are on the trailer going to Carlisle so I can't even test.
All my testing gauges are on the trailer going to Carlisle so I can't even test.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Roger- I'll double check this tomorrow but I'm certain I did it right.
I did the test with the resistor in place on a working gauge. Then removed it completely and the results were a gauge that pegged past the rivet. But to be on the safe side I'll give it a go again tomorrow.
I did the test with the resistor in place on a working gauge. Then removed it completely and the results were a gauge that pegged past the rivet. But to be on the safe side I'll give it a go again tomorrow.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Roger- I'll double check this tomorrow but I'm certain I did it right.
I did the test with the resistor in place on a working gauge. Then removed it completely and the results were a gauge that pegged past the rivet. But to be on the safe side I'll give it a go again tomorrow.
I did the test with the resistor in place on a working gauge. Then removed it completely and the results were a gauge that pegged past the rivet. But to be on the safe side I'll give it a go again tomorrow.
The more I think of it,it should act like a gauge minus the ground,because without the resistor there is NO connection to the neg terminal of the gauge. Doesn't that sound right ?
Looking at the back of the gauge , 3 oclock stud is the neg term for the gauge but the neg ground wire attaches to the 9 oclock term and jumpers over to the 3 stud term via the resistor...so without the resistor there is no ground connection.
How the heck did I come up with the results in my notes ?
Ernie , the part I don't quite get is the gauges that don't use a resistor,how does the ground connection get from the 9 stud to the 3 stud,does the 3 stud merely ground to the case ?
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Roger,
You are correct and here are the pictures I took.
Blown Resistor will look like this.
Grounded ohms wire will look like this.
Establishing what position the needle does what is a good way for anyone to isolate the problem before tearing the car apart.
How do the newer non resistance gauges work.... I don't have a clue Roger- I've never tore one apart and I've never had anyone want me to fix one. It may pick up the ground internally.
You are correct and here are the pictures I took.
Blown Resistor will look like this.
Grounded ohms wire will look like this.
Establishing what position the needle does what is a good way for anyone to isolate the problem before tearing the car apart.
How do the newer non resistance gauges work.... I don't have a clue Roger- I've never tore one apart and I've never had anyone want me to fix one. It may pick up the ground internally.
