The temperature gauge on my 71 starting bouncing around between 125 and 200 degrees when I was stopped at a red light. I pulled out and it leveled back out to normal around 190. Looked down a few miles later and it's dead, not working at all. Is it the sending unit or gauge that's gone bad. The car is all stock.

 

Probably the connector for the wire on the sensor. Easiest way to troubleshoot it is to turn the key on, disconnect the wire and ground it

 

Pull the wire off the sender. Touch it to ground. Turn on key. Gauge goes to full hot, sender bad. Gauge does not move, sender good, gauge bad.

 

Thanks guys.

 

Here's the procedure to diagnose temp gage problems:

Tests
A. Disconnect the green wire at the sending unit and turn on the ignition switch. The gauge hand should stay against the left side stop pin.

B.Ground the green wire disconnected from the sending unit. With the ignition switch still "ON," the gauge hand should swing across the dial to the right stop pin.

Corrective Measures
If the gauge hand does not stay to the left as in test "A", either the wire is grounded between the dash unit and the engine unit or the dash unit is defective.

Test further by disconnecting the dark green sending unit wire at the gauge. Turn on the ignition switch. If the gauge hand stays on the left hand stop pin, replace the disconnected wire. But, if the gauge hand still moves, replace the dash gauge.

If the gauge hand does not swing across the dial as in test "B", there is an open circuit in the wire between the sending unit and gauge, the gauge is defective, or current is not reaching the dash gauge.

Test further by grounding the sending unit terminal (dark green wire) of the dash gauge and turn "ON" the ignition switch. If the gauge hand now moves, replace the disconnected wire. If the gauge hand still does not move, connect a test lamp to a ground and to the power (pink wire) terminal of dash unit. If the lamp does not light, test the wire between the ignition switch and the dash unit by connecting a test lamp to the "Accessory" terminal at the ignition switch and to a ground. The test lamp should burn.

If the gauge hand operates correctly as in tests "A" and "B" but the gauge does not indicate temperature correctly, either the sending unit is defective or the dash gauge is out of calibration. Replace sending unit one of known accuracy. If gauge reading is still incorrect, replace dash unit.

If the gauge hand is at maximum at all times and test "A" and "B" indicate that the wiring and the dash unit are in condition, the sending unit is bad and needs replacement.

If the gauge hand will not move, the dash unit is bad, or incorrectly installed. Correct the installation or replace the gauge unit.

 

Thanks Kid Vette

 

How about when the Gauge only advances a little past half way when the sender lead (green wire) is grounded?

 

Find the sender wire where it attaches to the gauge, Ground it out there. That will tell you wire or gauge.

 

That is where I grounded it (at the gauge) and it still only advances half way so I suspect my brand new gauge is not working correctly, also, I verified 12 volts at the pink wire.

 

My gauge is stuck all the way to the right.The other week I was driving along and suddenly noticed my gauge was operating normally again.Stayed ok all through the ride,got home and shut 'er off.Next day as soon as I turned the key,the gauge went back all the way to the right and been that way since.

I tried unplugging the wire from the sensor(sender) and grounding it, turned the key to the ON position,same thing happened,stayed to the right------>

Could it be that my sensor is on the fritz?It came back to normal when she was hot and when she cooled off it was back fried.I just didn't feel to take my dash apart....

what do you guys think?

 

well it looks like I will have to take the dash apart,I tried a new sensor and the gauge stayed the same.

I might just try connecting a spare after market temp gauge I have laying around here from the hood and see if my sensor works ok.Then if that don't work i will be taking it apart

 

yup,start to take it apart tomorrow.Checked the sensor with new temp gauge and it works fine.

So it's either my gauge or the wire

 

Ok well i got one for ya. Gauge works "fine" most of the time, but sometimes it pegs to the right and stays that way. Then it'll come back to normal eventually, but when it does, to get an accurate reading, you have to let off the accelerator. If your on the gas at all it will pull the gauge to the left. How far the gauge moves back to the left depends on how much your on the gas. Any ideas?