Cooling issue

[b00mhower]

Issue started this morning on my way to work, my temp gauge had been reading at the quarter mark at all times but this morning it started at half then kept fluctuating up and down but it always came back down to half, while i was driving home it wemt all the way past h then back to normal. I'm thinking my tstat needs replaced but I'm hoping it's just my gauge being screwy, any thoughts?

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[Honky Kong jr]

Issue started this morning on my way to work, my temp gauge had been reading at the quarter mark at all times but this morning it started at half then kept fluctuating up and down but it always came back down to half, while i was driving home it wemt all the way past h then back to normal. I'm thinking my tstat needs replaced but I'm hoping it's just my gauge being screwy, any thoughts?

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Could be the thermostat but could also be the temp sender. Unhook the temp sender and ground it and see what the gauge reads should peg the gauge. Disconnected should be the inverse of grounded.

 

[4WDKC]

Issue started this morning on my way to work, my temp gauge had been reading at the quarter mark at all times but this morning it started at half then kept fluctuating up and down but it always came back down to half, while i was driving home it wemt all the way past h then back to normal. I'm thinking my tstat needs replaced but I'm hoping it's just my gauge being screwy, any thoughts?

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tstat or air in the system is my thought.

 

[b00mhower]

Could be the thermostat but could also be the temp sender. Unhook the temp sender and ground it and see what the gauge reads should peg the gauge. Disconnected should be the inverse of grounded.

Gonna go try that now

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[MikeB]

If the gauge was at 1/2 scale this morning when the engine was cool, you have a sender or gauge problem. You should first make sure the electrical connection to the sender is good.

If you understand resistance, resistors, and potentiometers, you can simulate the sender using the the resistances below to check your gauge.

For Truck Years: 1979 - 1990

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω

Also, you can use an ohm meter to check the resistance of your sender when the engine is cold (1365 ohms) or warm to hot (somewhere between 55-96 ohms. I would say +/- 10% is probably OK for any of the measurements.

 

[b00mhower]

If the gauge was at 1/2 scale this morning when the engine was cool, you have a sender or gauge problem. You should first make sure the electrical connection to the sender is good.

If you understand resistance, resistors, and potentiometers, you can simulate the sender using the the resistances below to check your gauge.

For Truck Years: 1979 - 1990

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω

Also, you can use an ohm meter to check the resistance of your sender when the engine is cold (1365 ohms) or warm to hot (somewhere between 55-96 ohms. I would say +/- 10% is probably OK for any of the measurements.

I'll have to grab a multimeter or wait until i go to work thanks for the resistance values !

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[b00mhower]

Could be the thermostat but could also be the temp sender. Unhook the temp sender and ground it and see what the gauge reads should peg the gauge. Disconnected should be the inverse of grounded.

sender did exactly that when I tested it nothing discontented and full pull grounded to the battery

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[Honky Kong jr]

You would need a variable resistor to test useing above Ohms numbers a volt meter won't do that but you could test you'd sensor with your meter with the sensor connected to the gauge and meter leads connected and engine running to see what for reading you get vs the gauge reading.

 

[chengny]

tstat or air in the system is my thought.

Low coolant level with entrained pockets of air (or combustion gases) causing erratic sensor outputs.

 

[gpmorgan]

You would need a variable resistor to test useing above Ohms numbers a volt meter won't do that but you could test you'd sensor with your meter with the sensor connected to the gauge and meter leads connected and engine running to see what for reading you get vs the gauge reading.

Not sure why you would need a variable resistor to check resistance.

 

[Honky Kong jr]

Not sure why you would need a variable resistor to check resistance.

To insure gauge is reading the proper tem at a prescribed ohm level. Not to check resistance but useing user given resistance to the gauge.

 

[gpmorgan]

My bad. I thought he was checking sender only. You probably need a new thermostat. Here's a link that might help. https://www.americanautowire.com/view-faq/general-motors-temperature-gauge-troubleshooting/

 

[b00mhower]

Thanks everyone for the input, got a new tstat will install in the morning when i do plugs. Will update

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[Honky Kong jr]

 

[b00mhower]

Sorry kinda late on the update but flush and fill and a new tstat did the trick, cleaned the sender connection while i was at it no harm in cleanliness eh?

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