Troubleshooting problems with temperature gauge

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Sirsmiley9

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Hello everyone
Ive got a temperature gauge which does not have any reading on a 1976 duster the fuel gauge and oil switch do however work, so I was looking for some advice finding the likely problem. Ive grounded the engine to the frame, and i didnt get it to work.
 
Since you have oil, that means you have a Ralley cluster, and that the IVR is inside the fuel gauge. Since oil and fuel work, that means the IVR is at least "working" if not accurate. Power for the T gauge comes off the cluster common to the fuel/ oil gauge and runs to one stud of the temp, through the gauge, out to the harness connector, through the bulkhead connector, and to the sender

The possibilities in no probable order are:

Break in the wire at the temp gauge connector or corrosion/ looseness there
Bad connection at the bulkhead connector terminal
Bad connection at the Cluster PC board wiring connector / pins
Bad connection at either of the temp guage studs
Bad temp gauge.

Likely your next project is removing the cluster.
You have a service manual? Go to MyMopar, download one free. The do not have 76, only up through 73. The wiring is quite different, but the mechanics are very similar.
Disconnect battery ground!!!!
 
I dont have a ralley i meant the oil pressure light not the gauge im not sure how much of a difference that makes however. It stopped working after i replaced the sending unit, because it seemed it was giving an inaccurate reading
 
The same I posted applies. The only difference really is the non-ralley has a "plug in" IVR If you ground the wire, it should peg the gauge
 
Make sure your new temp sending unit is for the gauge and not the idiot light.
 
LOL there is no such thing as an idiot light for temp in these girls. Oil? yeh.
 
Start the engine and allow to reach normal operating temp. Engine off. Pull purple wire off temp sender. Ohm meter leads on sender contact post and ground should show somewhere between 20 and 40 ohms if the sender is good. With ignition switch on a digital volts meter between the purple wire and ground will show a pulsing voltage that averages 5 to 6 volts if the wiring and gauge are good. If you do find the pulsing voltage a short wire with alligator clips from the wire terminal to ground should send the gauge needle quickly to 'H' with ignition switch turned to on. If you dont find the pulse voltage you'll need to check that purple wire at engine harness connector, bulk head connector, and all the way to the gauge. The gauges are held to contact a printed circuit board with stamped speedy nuts. Loosened nuts causing a dead gauge has been found a few times.
I know your model of fuel gauge measures 13.5 approx' ohms post to post. I dont know if the temp gauge ever changed from 20 ohm to 13 ohm type. In any case the gauge will have continuity through it or be open. Open or continuity between a post and the gauge can = replace it. In a 73 Valiant we had... a faulty gauge voltage limiter was causing wild needle swings in that temp gauge. A solid state regulator cured that but... the damage was done. The temp gauge died about 6 months later. I have to recommend you replace the limiter if/when you pull the inst' panel.
 
When this happened with my 73 swinger it was a loose pin on the back of the circuit board.

I’m afraid pulling the cluster is going to be necessary to diagnose/repair this problem.
 
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