How to test temp sender and gauge with only a multimeter?

[edbods]

I finally got my car fired up and man it's a great feeling getting it running again. But unfortunately, I noticed that my temp gauge barely moves from stone cold even though the engine is scalding hot. The fuel gauge works fine, which implies something wrong along the sender circuit. Is there any way to test the gauge and sender with just a multimeter only? I took the gauge out of the dash and got 20 ohms resistance between the two studs with the needle at its lowest point, dunno if that's what's meant to show up though. Unfortunately, at the moment I can't get easy access to the bits and pieces needed to make my own C-3826 tester, or at least, I don't know what bits to cobble together to make a homemade version. Also, the sender appears to take a female spade terminal/connector, instead of the screw down ones that seem to be on later models, not sure if that changes anything.

 

[Davea Lux]

What year car is this? You can test the gauge by taking the lead loose from the block sensor and grounding it out to the block. This should peg the gauge to the hot side with the key on, don't leave the key for very long as this could fry the gauge. Since you have some resistance, the gauge is probably ok. If the gauge pegs, most likely the sensor in the block is bad. If the gauge does not move, trace the wiring back to it and check the circuit board on the back of the instrument cluster. Sometimes the circuit pathways get fractured after long use. Since you have a working gas gauge, the cluster regulator is working. Check the gauge for cob webs as those can block the movement of the gauge needle on a vehicle that has long been inactive.

From the sensor, it should read about 80 ohms at 120F, 32 ohms at 170F and 13.5 ohms t 230F. The gauge goes higher as the resistance drops, with little or no resistance, the gauge is pegged. Check the sensor with the lead removed on a hot engine, if you have high resistance once the car is warmed up, the sensor is dead.

Dave

 

[Big_John]

Unfortunately, at the moment I can't get easy access to the bits and pieces needed to make my own C-3826 tester, or at least, I don't know what bits to cobble together to make a homemade version.

Buy one of these instead. Ford 1955-1986, 73-10 ohm Fuel Gauge Tester - 992-3FA - National Parts Depot

Under $30. Yea, yea, it's for a Ford. They use the same resistor values and they should market it to Mopar guys.

 

[edbods]

What year car is this

Oops. It's a 67 Phoenix/67 Fury with the 383 engine. But the temp sender looks like a 66 and earlier model, takes a female spade connector. Hooks up to a 66 Polara/Monaco gauge.
@Big_John thanks for that. Gonna see if there's a local version since shipping will kill me for such a cheap tester. Don't have to worry about using OG mopar stuff with me, I try to where I can but at the end of the day I'm not a concours purist.

Edit: and whaddya know, people sell them here too! Seems like the shipping is already part of the price though, 75 bucks RIP.