coolant temp question
Thread Starter
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 243
From: Northern VA
coolant temp question
My dash indicator is showing high temps. My temp gauge on my DFI system which pulls temp from the intake is much lower. I know the two sensors will always be a little different but the difference is huge now. I have had problems in the past that was caused by an air pocket in the head causing the dash sensor to read high. I have packed the system and replaced the passenger side head sensor twice. Could a bad t-stat cause this?
Pro
Joined: May 2006
Posts: 637
Likes: 0
My dash indicator is showing high temps. My temp gauge on my DFI system which pulls temp from the intake is much lower. I know the two sensors will always be a little different but the difference is huge now. I have had problems in the past that was caused by an air pocket in the head causing the dash sensor to read high. I have packed the system and replaced the passenger side head sensor twice. Could a bad t-stat cause this?
If you have the automatic A-C controller C68, you can press and hold the fan up and down buttons a few seconds till it shows 00-, then press the fan button in the middle (???, could be the fan up button, I don´t recall???), it will probably show 00, then continue pressing fan up button till you come to "16", then press fan button in the middle and it shows your actual temp.
A stuck T-stat closed will only circulate coolant in the engine, stuck open will circulate coolant through the engine and rad constantly wich would cause the engine to not reach the ideal temp.
This will result in the engine not going into closed loop with other problems like running rich for example.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
'89 doesn't have this feature.
Dash temperature is derived from a thermistor in the right head meaning that as it warms up, the resistance decreases so the voltage from the Dash drops and that drop is used to calculate coolant temp. Quick test is to disconnect the harness at the sender and the open circuit should produce "Lo" on the Display. Ground the wire and it should give you something around 300. If that works, ohm out the wire between the Sender and the Display, Pin D4. If it shows a completed circuit, compare the Display with the Coolant Temp Sensor with a scanner - if that agrees with your DFI readout, replace the Cluster.
Dash temperature is derived from a thermistor in the right head meaning that as it warms up, the resistance decreases so the voltage from the Dash drops and that drop is used to calculate coolant temp. Quick test is to disconnect the harness at the sender and the open circuit should produce "Lo" on the Display. Ground the wire and it should give you something around 300. If that works, ohm out the wire between the Sender and the Display, Pin D4. If it shows a completed circuit, compare the Display with the Coolant Temp Sensor with a scanner - if that agrees with your DFI readout, replace the Cluster.
Pro
Joined: May 2006
Posts: 637
Likes: 0
'89 doesn't have this feature.
Dash temperature is derived from a thermistor in the right head meaning that as it warms up, the resistance decreases so the voltage from the Dash drops and that drop is used to calculate coolant temp. Quick test is to disconnect the harness at the sender and the open circuit should produce "Lo" on the Display. Ground the wire and it should give you something around 300. If that works, ohm out the wire between the Sender and the Display, Pin D4. If it shows a completed circuit, compare the Display with the Coolant Temp Sensor with a scanner - if that agrees with your DFI readout, replace the Cluster.
Dash temperature is derived from a thermistor in the right head meaning that as it warms up, the resistance decreases so the voltage from the Dash drops and that drop is used to calculate coolant temp. Quick test is to disconnect the harness at the sender and the open circuit should produce "Lo" on the Display. Ground the wire and it should give you something around 300. If that works, ohm out the wire between the Sender and the Display, Pin D4. If it shows a completed circuit, compare the Display with the Coolant Temp Sensor with a scanner - if that agrees with your DFI readout, replace the Cluster.
Well, I learned something new about the 89, always good to know in case of ever buying one.
