temp gauge not working

[moparfanatic56]

I have read some older posts on this issues and tried the suggestions but to no avail. This is a standard gauge cluster in a 72 dart that has a new circuit board and the ivr is new also. I have made the temp gauge work I believe by grounding the sensor on the brass just below the threaded pin that the harness attaches to but if I try to ground any lower nothing happen, I am running a ld340 intake and I have the ground from the block to the firewall. The sensor is good as l get temp readings when connected to an aftermarket mechanical gauge.
I am also having trouble with the fuel gauge not working also. I grounded the sensor wire and the gauge went to full but when I tried to ground the sending unit nothing happened, I do not currently have the metal ground strap that bridges the 2 fuel lines.
So my question is could I possibly be having a grounding issue with the cluster?
Thanks

 

[67Dart273]

Might be as simple as a little corrosion in the connector. Try finding something to scrape it or if not, just push/ pull it on /off the sensor a few times. To ground try an alligator clip wire inserted into the terminal. Also wiggle the terminal it may be broken inside the molding

Assuming the fuel gauge works, other problems could be in the bulkhead connector, the cluster connector, and the nuts on the studs of the gauge.

 

[moparfanatic56]

Might be as simple as a little corrosion in the connector. Try finding something to scrape it or if not, just push/ pull it on /off the sensor a few times. To ground try an alligator clip wire inserted into the terminal. Also wiggle the terminal it may be broken inside the molding

Assuming the fuel gauge works, other problems could be in the bulkhead connector, the cluster connector, and the nuts on the studs of the gauge.

a little more infi I should have included, new sending unit, new temp sensor and new m&h wiring harness front to back and underdash. also new fuel lines, new fuel tank.

 

[Professor Fate]

I do not currently have the metal ground strap that bridges the 2 fuel lines.
So my question is could I possibly be having a grounding issue with the cluster?

I think you answered your own question. Get the strap or ground the tank some other way, THEN see if the fuel gauge problem persists.

 

[harrisonm]

I have a thought on the temp gauge problem. You said that the gauge worked when you grounded the temp sending unit on the top part. That is the same as grounding the wire. The gauge will work when current flows through the gauge to the temp sensor and into the grounded engine. If the gauge works when you ground where you did, I am guessing that you either have a bad temp sending unit (even if it is new), or someone has used so much teflon tape or silicone goop when installing it that it cannot ground out to the engine. That means you do not have a complete circuit and the gauge will not work.

FWIW, people call the temp, fuel and oil pressure sensors sending units, but they are not. They don't actually "send" anything. They are variable resistance switches. The IVR sends current through the temp gauge and then into the temp sensor. With the temp switch that is screwed into the intake, when the engine is cold the resistor in the switch allows no current to flow through it into the engine. That means there is no current flowing through the bi-metal coil in the gauge. That means no movement on the gauge. The warmer the sensor gets, the more current it will allow to flow into the grounded engine. But if you have used enough of whatever type of sealant when installing the sensor, it will not allow current to flow through it and into the block even if the engine is properly grounded.

Just a thought. Check it out.