Too hot to handle

[mhuppertz]

Changed my water temp sensor and when I drive around town in the high 90's is registers "HOT" and shuts off the A/C if I sit waiting to get fuel or something.

The fans are spinning but not like I think they should be in a hot engine situation.

Could it be a fan controller?

I can't seem to find reference to a controller or a replacement part number.

[Ronnie]

What is the coolant temperature reading on the CRT?

[Barney Eaton]

Here is the cooling fan schematic from the 1990.......I believe the 1988 is a little different but the other years are the same.

The temp sensor send information to the ECM and the ECM picks the relays to control the fans.

I believe there is three stages.......all depending on engine temp and if the A/C is on.

(1) engine side fan only

(2) both fans but running at 1/2 speed (this is done with the relays....placing the fans in series )

(3) both fans at full speed by giving both fans a full 12v

Your problem (assuming the temp sending unit is good)  could be a bad relay or a problem with the ECM

NOTE  what I call the ECM (engine control module) is the PCM (powertrain control module) in this drawing

Edited June 26, 2018 by Barney Eaton (see edit history)

[padgett]

What is ED04 reading ? Over 100C ? One thing I've done to all of mine is to go to a 180 'stat and reprogram the fans for LO at 185F and HI at 189F

[ski.dive]

  PATGETT- 

 

I have a 180* thermostat===How do you reprogram the fans for LO at 185F and HI at 189F ??

[padgett]

You have to copy the PROM program and change four bytes. Which three depends on which PROM you have. It does require a certain amount of electronic equipment. Or you can add an external thermostatic switch.