Operating Temp on 89 L98 Stock
Instructor
Joined: May 2012
Posts: 194
Likes: 1
From: Lawndale CA
This information needs to be in a sticky as the operating temps scare most people.
Stock ECU cooling fan control values are as follows.
Cooling fan on = 230.
Cooling fan off = 200.
If you see anything past 235 you should check/clean your radiator for debris or obstructions.
If these values concern you, there are some options available to you. Aluminum radiators, lower temp thermostats, electric water pumps, auxilliary fan relays, and reprogramming the ecu for lower temps.
Stock ECU cooling fan control values are as follows.
Cooling fan on = 230.
Cooling fan off = 200.
If you see anything past 235 you should check/clean your radiator for debris or obstructions.
If these values concern you, there are some options available to you. Aluminum radiators, lower temp thermostats, electric water pumps, auxilliary fan relays, and reprogramming the ecu for lower temps.
Last edited by TTA579; Jan 30, 2013 at 11:07 AM.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Stock specs for an '89 is 226 for the Main; 228 for the Aux. The Aux should rarely if ever come on (if it even has the Option). The Main Signal is from the Coolant Temp Sensor which you view with a scanner and your Display can be as much as 5 Degrees warmer. With the Main Fan running it should cool down. It wasn't designed to heat up and if it does, there is some other problem. If 226 doesn't do it for you, simply run the a/c. That's designed to keep the liquid in the Condenser at or below 100 degrees so the fan will come on sooner and run longer with your Coolant Temps averaging 10 to 12 degrees less as long as it's running. If that doesn't happen, something is broken. The factory radiator is aluminum. Sounds like your Vette was ok if the a/c was off. Test the Aux Fan by blocking air flow and see what temp it clicks on at, but from the Factory, these things were designed to run so little, there's little reason for anything to be worn out. Common overheating issues with this Year are caused by a blown or weeping head gasket; overtaxed alternator (check your voltage - the fan can't move enough air if it's below Battery and that happens real fast if both fans are cranking. Best to resist any urge to make it run this way without an electrical upgrade).
Instructor
Joined: Jan 2013
Posts: 212
Likes: 0
i was also looking for this information. my car seems to be all over the place. its winter here (normal temps around freezing point) and i am anywhere from 185-220 degrees. it worries me that the car ever gets above 200 in this cold weather. sitting in traffic with the air on during the middle of the summer will be taxing. my fan is pretty random. seems to jump on at any temp above 200 and turn off once its back below 200. sorry about the rant! 
