ranger390v
Member
Posts: 34
Loc: Pittsburgh,PA,USA
Reg: 11-13-02
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 06-27-08 01:00 PM - Post#1465589
Hi. 1992 Chevy G20 Van.
Either the temperature gauge or the sending unit is going bad... It seems I have two sensors, one for the gauge (left side of engine) and one for the OVERHEAT light (top of engine, near thermostat).
My gauge will sometimes jump to hot when the engine is cold or stay at cold when the engine is warmed up. Sometimes the gauge will move slowly all the way up or down the scale.
I need to pull the inside van cowling to test it with an ohm meter.... but my question is.....
If the sending unit is bad and I replace it, will the hole it goes into leak radiator fluid? What does the sensor measure? Coolant temp or block temp?
Thanks.
| 1992 Chevy G20 van
1992 Chevy/Geo Storm
1989 Chevy Beretta |
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 someotherguy
Senior Moderator
Posts: 29799
Loc: Texas
Reg: 08-01-03
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06-27-08 01:17 PM - Post#1465603
In response to ranger390v
The one on the head is for the dashboard gauge, the one near the thermostat housing is actually the CTS (coolant temperature sender) for the computer.
Going momentarily full hot even when the engine is cold is likely an open circuit. Could be as simple as a flaky connection, or of course faulty sender, wiring, or gauge.
You'll loose a little bit of coolant while replacing the sender, but nothing to worry about - as long as you work on it cold, so it's not pressurized. 
The factory manual suggests using a specialized tester for this circuit, but one can interpret what should read "cold" and "hot" on the gauge from the instructions. When the gauge should read "cold", you can expect to see a reading from the sender of around 1400 ohms. At the "hot" end, around 55 ohms. So you could test the sender when it's cold and hope to see something in the neighborhood of 1400 ohms. You wouldn't be able to get it to read full hot under normal conditions, but if you warmed it up and saw something considerably less than 1400 ohms and greater than 50 ohms, and the reading is consistent, then the sender is probably okay. Hope that helps. 
Richard
| 06 Silverado ISS / 06 Silverado SS / 06 300C SRT8 / 93 C3500 dually |
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ranger390v
Member
Posts: 34
Loc: Pittsburgh,PA,USA
Reg: 11-13-02
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06-28-08 06:30 PM - Post#1466338
In response to someotherguy
Thanks, your description was perfect.... on my outboard motor the sender just mounts into the head, there is no passage to the cooling water jackets on it, the end of the sensor sits against the head in the hole. I was hoping this was the same, just in case I have a problem removing it on this old engine. Thanks for the ohmmeter readings.
| 1992 Chevy G20 van
1992 Chevy/Geo Storm
1989 Chevy Beretta |
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