Bad sensor or bad gauge?

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doogievlg

doogievlg

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My temperature gauge is reading 230°. I put the temp gun on it and the actual temperature is 160. I grounded the wire from the sensor and it maxed out which tells me the gauge is working. Does this sound like a sensor issue or gauge issue.
 
doogievlg said:
Aftermarket autometer. Factory gauge bit the dust so I’ve been relying on this one. I need to fix the OEM gauge but that doesn’t seem like a quick project.
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If the gauge drops when you unplug the sensor, it seems it would have to be a sensor issue.
 
TrailBeast said:
If the gauge drops when you unplug the sensor, it seems it would have to be a sensor issue.
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It would stay at zero until I grounded the wire then it would jump to max.

Dumb question here but what is the correct way to wire the sender? It’s similar to this one but it has a black insulator instead of white.

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If it goes full when grounding wire, key on and zero when pulled away from ground, it's a good bet you have a bad sensor. Use an ohm meter, red lead where wire connects, black on sensor body should get some resistance value to check against manufacturer specs.
 
stroker416 said:
If it goes full when grounding wire, key on and zero when pulled away from ground, it's a good bet you have a bad sensor. Use an ohm meter, red lead where wire connects, black on sensor body should get some resistance value to check against manufacturer specs.
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I’ll grab another sensor this week and throw it on.
 
doogievlg said:
It would stay at zero until I grounded the wire then it would jump to max.

Dumb question here but what is the correct way to wire the sender? It’s similar to this one but it has a black insulator instead of white.

View attachment 1716143509

View attachment 1716143510
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Most sender units just have one wire that goes directly to the gauge.
Your test of grounding that wire generally means the gauge is working like it should.

Note that the body of that sender must be grounded for it to function, so products like teflon tape are a no no.
 
TrailBeast said:
Most sender units just have one wire that goes directly to the gauge.
Your test of grounding that wire generally means the gauge is working like it should.

Note that the body of that sender must be grounded for it to function, so products like teflon tape are a no no.
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I did a fair amount of plumbing work at my last job so there is a good chance I put tape on the threads here too.
 
doogievlg said:
I did a fair amount of plumbing work at my last job so there is a good chance I put tape on the threads here
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I'm in the Teflon tape is not the issue camp.

As a plumber have you ever pulled apart a pipe and not been able to see metal through the tape?

IMHO it's easy to test. Check resistance from the body of the sender to ground. If you have more than 0.1 to 0.4 ohms then there might be an issue (basically what the meter reads when the 2 leads are shorted together)
 
Dana67Dart said:
I'm in the Teflon tape is not the issue camp.

As a plumber have you ever pulled apart a pipe and not been able to see metal through the tape?

IMHO it's easy to test. Check resistance from the body of the sender to ground. If you have more than 0.1 to 0.4 ohms then there might be an issue (basically what the meter reads when the 2 leads are shorted together)
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I’ll see if I can find my old electric meter tonight.
 
Dana67Dart said:
I'm in the Teflon tape is not the issue camp.
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I am as well, but it's easy to check, just take your ohmeter and measure from the shell of the sender to the block. Zero ohms or close. I believe that more senders are ruined by OVER tightening, which can distort the housing and damage/ put pressure on the thermister
 
If you have some potentiometers available you could test the entire circuit, as long as you know the correct value of the thermistor in question.

I recently purchased two 150 ohm resistors from DigiKey, and by connecting them in series I've been able to test/check the gauges in the Aussie Valiant I'm working on (factory VDO gauges).
 
If aftermarket much prefer mechanical gauges, over electric ones
 
doogievlg said:
I’ll see if I can find my old electric meter tonight.
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Pulled the old sending unit out and no tape on it. Threw a new sending unit in it and it still had the same problem. Checked the ground on the gauges just for fun and it’s fine. I’m at a loss here. Only thing I could think of is I just got a bad gauge.
 
Disconnect the sender wire from the gauge.

Then check the resistance from the wire to chassis ground.

There could be a short or a high resistance in the wire
 
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