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Temperature gauge is not working

Tiny
BW_OBS
  • MEMBER
  • 1993 CHEVROLET 1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 204,000 MILES
I grounded the pigtail and the gauge went to hot so I know everything going to the cluster is good. I tested the resistance on the temperature switch and it was around 2000 ohms cold and it dropped when I put it in hot water. Don't know where to go from here. Truck listed above is a C1500 350.
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Friday, May 28th, 2021 AT 10:24 AM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,489 POSTS
Hi,

First, it sounds like the ohms were correct at room temperature. How far did it drop? If you look at the attached pic (pic 1), it shows the range based on temperature.

If the readings seem to parallel what you found, I need you to disconnect the sensor wiring connector. There should be two wires to it, a yellow and a black.

Check the yellow wire for power with the key in the run position. You should see a 5v reference signal to the sensor.

Let me know what you find.

Joe
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Friday, May 28th, 2021 AT 7:58 PM
Tiny
BW_OBS
  • MEMBER
  • 3 POSTS
The 2 wire ECT on the intake is fine and working properly. It’s the one on the DS head with a single dark green wire that goes to the gauge that isn’t working.
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Saturday, May 29th, 2021 AT 12:12 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,489 POSTS
Hi,

Okay, on the firewall under the hood is a large connector plug that sends power into the vehicle. Disconnect the battery and then disconnect that plug. Pin 35 is what covers the gauge. See if there is a corrosion issue or damage at that connector.

You mentioned the dark green wire. That is the one I am referring to. It runs to the cluster. Pic 1 below shows the wiring between the sensor and the cluster.

See pic 2 shows power from the firewall to the panel. I highlighted the green wire. See if there are any breaks at any point.

Let me know.

Joe
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Saturday, May 29th, 2021 AT 6:02 PM
Tiny
BW_OBS
  • MEMBER
  • 3 POSTS
There are no breaks in the wire. The gauge goes to hot when I ground the connector.
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Sunday, May 30th, 2021 AT 6:57 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,489 POSTS
Do me a favor. Disconnect the battery and check the power supply wire for continuity to ground. Also, with the battery connected, check to see if there is power at the ground wire. Something is shorting unless the gauge itself is bad.

Let me know.
Joe
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Sunday, May 30th, 2021 AT 6:03 PM

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