Temp Gauge Sender issues

[SlantedMark4]

My temp gauge didn't work, so I have replaced the dash voltage regulator which made my temp gauge move again, thankfully, but when I started the engine, the temp gauge went up to 250° and back to 0° when the engine was warmed up. I've thought the temp sender was bad, so I have replaced this one aswell. Now, the temp gauge doesn't work at all while everything else works fine. The temp gauge has light, so I don't think it's a cluster problem but either the sender or the thermostat. The thing is, I have replaced the thermostat 2 years ago..
Has anyone an idea what I have to check next? I'm a bit confused with electrical things...
We're talking about a 1974 Slant Six powered Valiant 4 door with 65amp alternator factory wiring.

 

[halifaxhops]

Check the sender wire itself.

 

[Syleng1]

What he said and check your grounds for engine to battery and engine to chassis. Chassis to battery.
Check your fire wall block connection. Make sure the connection for the wires are clean and in good contact. It’s a very simple system that can go silly when dirty.

 

[Mike69cuda]

The aftermarket senders are bad out of the box sometime. Some go bad after a few days. I finally bought an OEM one from a Chrysler dealer and it has worked fine since.

I would try the following.

1. If you have an ohmmeter, check the resistance of the sender. It should read about 60-80 ohms at cold. It should read about 20-30 with the engine warm. Measure from the center pin of the sender to the case of the sender.

I have seen a number of them read about 2000 ohms when they go bad..

Harbor Freight sells ohmmeter for about $5 as I recall, or Lowe’s has nice ones for about $30. Watch some YouTube videos if you don’t know how to use it.

2. Ground the wire going to the sender to the sender case or engine block and see if the gauge moves. Don’t leave it grounded more than a few seconds or you may damage gauge.Helps to have an assistant to watch the gauge.

 

[Professor Fate]

Did you use sealant on the sensor threads? Try putting it in "clean". It uses NPT threads which should seal fine without sealant (tape, pipe dope, RTV, whatever). Sealants can cause issues with the ground.
Check the wire as mentioned above- if you ground it briefly, the gauge should move. That confirms that you're getting current to the sensor. Then check continuity from the sensor body to the engine block. If no continuity, pull the sensor and clean the threads and reinstall.

 

[SlantedMark4]

Did you use sealant on the sensor threads? Try putting it in "clean". It uses NPT threads which should seal fine without sealant (tape, pipe dope, RTV, whatever). Sealants can cause issues with the ground.
Check the wire as mentioned above- if you ground it briefly, the gauge should move. That confirms that you're getting current to the sensor. Then check continuity from the sensor body to the engine block. If no continuity, pull the sensor and clean the threads and reinstall.

I've added some extra sealant tape so this might be the problem. Im gonna remove it and see that happens, thank you!

 

[Dana67Dart]

My temp gauge didn't work, so I have replaced the dash voltage regulator

PLEASE ANSWER EACH QUESTION...
And watch this video



Did the fuel gauge work at that time?

but when I started the engine, the temp gauge went up to 250° and back to 0° when the engine was warmed up.

Was the engine cold at that time?
Did you allow the engine to warm up to normal operating temp as it went down to 0?

Is 250 pegged to the right?

If so how long did it stay there?

Are we talking deg F or deg C?

I've thought the temp sender was bad, so I have replaced this one aswell

Give us the part number of the sender you had and the replacement

Now, the temp gauge doesn't work at all while everything else works fine.

Define everything else.

Only the fuel gauge and if so equipped an oil gauge ( not idiot light type oil light) have anything in common with the temp gauge

The temp gauge has light, so I don't think it's a cluster problem but either the sender or the thermostat.

The lighting in the cluster has little to do with this. If the ground to the cluster was missing the lights would not light and the temp and gas and if so equipped the oil gauges would peg and eventually burn out.

The thing is, I have replaced the thermostat 2 years ago..

The thermostat does not have anything to do with this. Check the engine temp at the base of the thermostat housing or at the base of the temp sender with a infrared temp gun or other temp probe that can make good contact.