Temperature gauge does not read anything, though the car warms up fine - Third Generation Pontiac Firebird (1982 - 1992) - Firebird Nation

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Temperature gauge does not read anything, though the car warms up fine

sensor Temp Sending Unit problem 5.0 TPI 305 Trans Am gauge problem temperature gauge not working

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3 replies to this topic

#1 blondeau67

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  • Year: 1987
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Posted 5 days ago

Hello all,

 

I have a 1987 Trans Am with the 305 TPI, vin F. I just replaced the water pump, and as I was testing everything I noticed that my temp gauge in the gauge cluster does not rise at all. This is unlike the other forums that I have read where the gauge gets pinned at max or wobbles around and stuff. I have read that this can be caused by the sending unit, located in the drivers side cylinder head, however I cannot find that anywhere on my car. No green wire, no brass/copper hex screwed into the head, nothing. I really don't want to drive this car without a temp reading, especially while it's still hot where I am. 

 

Before I realized it could be the sending unit I was looking for the sensor that hooks into a hose coming out of the top of the water pump. This sensor is for the fans, correct? Or could I have damaged the sensor and caused the gauge to quit working while changing the water pump? I am pretty sure this sensor is just for the ECU to tell when to turn the fans on though. Here's a picture of the connector though, just in case, this is on top of the water pump.

 

Again, the gauge just doesn't work. No movement at any point during a full heat cycle. Plus I can't even find a sending unit on either cylinder head, so I am so very confused. 

 

Could it also just be the gauge went bad? Any help would be appreciated, I have not been able to drive this car in weeks and I am dying to do so, but without a temp reading I am nervous to take it very far from the house.

 

Thanks in advance!



#2 Injuneer

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Posted 5 days ago

The dash gauge indicates temperature based on the resistance of the sensor.  High resistance means low temperature.  Something as simple as the single wire being disconnected from the sensor produces high (actually infinite) resistance, and the gauge will not move off the lowest reading.
 

If you can find the sensor, you can check the resistance vs. temperature.  If you can find the single wire, you can test for 12 volts between the wire and a ground.

 

This is info for a 4th Gen, but the basics are similar.

 

http://shbox.com/1/temp_sensor2.jpg
 

http://shbox.com/1/4..._tech2.html#ect


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 sea dog

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Posted 5 days ago

Coolant temp sender for gauge is located on left side of engine. It's way down low near the back of the engine block.

 

If you would go to the 3rd gen tech section. Then hit the master index near the top, when new page opens, 1st on the list is 88 GM service manual. It's actually the 88 firebird manual.

 

Open it and download the 88 firebird service manual. Section 8 is the wiring diagram section. A diagram of cts location is on page 8A-201-8 figure A

 

Wiring diagram for coolant gauge & sender is on page 8A-81-2 And 88 service manual will share 99% of info with 87.



#4 blondeau67

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Posted 4 days ago

Coolant temp sender for gauge is located on left side of engine. It's way down low near the back of the engine block.

 

If you would go to the 3rd gen tech section. Then hit the master index near the top, when new page opens, 1st on the list is 88 GM service manual. It's actually the 88 firebird manual.

 

Open it and download the 88 firebird service manual. Section 8 is the wiring diagram section. A diagram of cts location is on page 8A-201-8 figure A

 

Wiring diagram for coolant gauge & sender is on page 8A-81-2 And 88 service manual will share 99% of info with 87.

And this is why you're a Master Tech and an admin. Thanks a ton, I'll check it out when I get the chance, may not be able to for a bit because of work but we'll see. 







Also tagged with one or more of these keywords: sensor, Temp Sending Unit problem, 5.0 TPI, 305, Trans Am gauge problem, temperature gauge not working

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