AutoMeter Cooleant temp gauge

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Sep 17, 2006
Santa Rosa, CA
Anyone know how to test an AutoMeter water temperature sending unit for operation? Warm up the engine and test voltage? ohms?

My coolant temp gauge is dead. I've tested the gauge according to AutoMeter's instructions and it appears to work, I've continuity tested the wires and they seem good, so I now need to test the sensor.

Just hook your meter up to it and read ohms (resistance) and watch it as it heats up. Does the needle move at all when it is hooked up to the gauge? Was it working before and all the sudden stopped? Maybe it is shorted? How many leads does the sensor have?
The sensor has two leads, one goes to ground. The meter does move to about 100 on power up and if I ground the S lead it will peg - which is apparently what it is supposed to do.

I put the meter on the sensor and see if I get some resistance change across it.

OK, it reads 1 all the time, I guess it's dead.

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So one wire comes off a attaches to ground? You should be able to stick one lead on it and a screw in engine bay and read basically 0 ohms. Then when you measure across both leads with the wire connected to ground you get 1 ohm? Try measuring to each lead and the metal housing or the block. The one should read an open and the one with the ground wire should be zero. It seems like 1 ohms should peg the gauge just about the same is a short.
It's not reading one ohm, it reading the 1 that indicates open circuit - isn't that what 1 means on a simple multimeter? I'm not sure I follow all your instructions but I'll give it a try.

Yeah if it is reading a open on both leads then it is probably toast. Maybe you can order just the sender but might not be calibrated. Maybe check out autometer's webpage. goodluck
Thanks for the help. AutoMeter is usually pretty good about sending out replacement sending units. It's strange that it would be bad out of the box - but you never know.

You could pull it and try the hot water on the stove with the meter attached.
maybe a crazy comment but you do have power running to the gauage and also a ground when you are trying to determine if the gauage is working? I've used automter for a long time, both mechanical and electrical , without issue. You may have a lemon but I would say autometer is a very good product.
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Yes, I check 12v and ground at the gauge, I think the lower primates that installed the engine damaged the sensor when they put it in.

yo dog,

Here's an idea: you can test the entire circuit (power source, ground path, meter and wires) by putting your test light across the sensor connections. You will get three things: 1) verification if there's power through the meter to the sensor 2) if the test light lights, your ground path is also good. As a bonus, 3) your test light has some resistance and you may notice some defelection in the gauge.

If you get the test lamp to light, replace the sensor. It's pretty quick.


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