View Full Version : Coolant Question

01-07-09, 04:30 PM
Can someone tell me what temps the fans are programmed to start. Is there anyway of checking to be sure the fans are coming on without running the engine to that point?

01-07-09, 04:32 PM
Sorry, 99 Deville with Northstar 4.6L

01-07-09, 09:10 PM
Fans come on at 224. They run anytime the A/C is on, so turn on the defroster (A/C always runs in defrost mode) and see if they are on.

01-07-09, 09:26 PM
.......the fans go to slow at 224 or in any HVAC mode which also runs the a/c compressor. Fans go to high at 236 coolant or 304 transmission fluid temperatures. There are 2 relays and 2 fuses in the underhood box which control fan speeds......series (voltage drop) for slow, parallel for fast. Fan excitation is always hot, so one or both fans can run even if the ignition is off.

01-07-09, 09:57 PM
Fans go to high at 236 coolant
Hey Sub, are you sure? I thought it was 229.

01-08-09, 06:22 PM
2002 STS FSM.....

Fans to slow at 223 degrees, or any a/c command function.
Fans to fast at 234 degrees (coolant) or 304 degrees (transmission fluid).
Coolant light at 256 degrees.
Fans to fast and cylinder disable sequence at 268 degrees coolant.

(and buried in the text - normal coolant temps and vehicle speed over 45, fans off)

So, the engine is designed to function in "camel mode" at 268 degrees, and get you home. (30 miles ???)

01-08-09, 06:45 PM
I think they change these parameters every few years just to confuse us (me).

02-04-09, 12:54 PM
at what temp coolant is considered to be overheat on 98 northstar in deville? what temps are normal?

02-04-09, 02:08 PM
jaqueline, Your car uses a 190 degree thermostat which is set to begin opening at 188 degrees and to be fully open at 206. Normal everyday driving should produce about 200 degrees + or -. A long traffic stop might see 223 degrees, when the cooling fans come on in slow and bring the temp down to about 215. Fans go to fast at the unlikely temp of 236. The pressure cap on the cooling system is set at either 16 or 18 pounds/square inch which puts the coolant boil point at around 264 degrees, overheat. Fans will also run in slow for any heating/cooling setting which calls for the air conditioning compressor to run.