I have been trying to figure out the locations and functions of all the coolant sensors on my 89 GTA. I have read old posts and been able to see that the sensor on the driver's side head is for the temp. gauge,the sensor on the passenger head is for the fan, but I also have a sensor on the passenger side of the block and I dont know what this is for. Are there any more coolant related sensors? Also how does the secondary fan come on? The reason I am asking is because i just built my 383 and the sensor in my passenger head was broken when I bought the car. Any help would be great. Thanks guys

 

There's a coolant sensor on the intake manifold near the T-Stat housing. It gives an actual temp reading.

Then there's the coolant switch that between the #6 and #8 spark plugs. It gives a ground signal to the 2nd fan relay. The A/C pressure switch located on the aluminum line below the passenger strut tower also gives a gound signal to the 2nd fan relay. I think the switch is on at 220 (or something like that) and off at 200 (I think). And the pressure switch is on at 216 (maybe 261??) PSI.

Then, there's the coolant temp sender. If the ECM fails to give the temp gauge a ground, the sender will, once it warms up. It's just a backup.

The ECM controls the 1st fan and monitors the 2nd fan by looking for a gound by the temp switch or the pressure switch.

The round can looking sensor on the block down by the starter is the knock sensor. It is also called the ESC (Electronic Spark Control) sensor. It senses any detonation and signals the ECM to retard the timing. It has the same type of connector as the coolant switch, so don't get them confused.

 

The sensor on my passenger side head is broken. Do you have any idea what the part number is or at least what the exact name of this sensor is. Thanks for you help so far. Also is there any difference between the wires for the knock sensor and the sensor in the head so I don't hook up the wrong wire. Thanks