On my 2003 Envoy, I started having overheating problems. I replaced the fan clutch but the problem persists. The speed of the fan is too slow to cool the ENGINE. I need to know, 1st, if there is a fan relay switch and how it works? 2nd, where is it at so I can check it. Also, if it can be diagnosed, what do I look for? Any help will be appreciated.
If the fan is not operating at the proper speed/function, a diagnostic trouble code should set.
The first thing you should do is to scan the computer for any trouble codes with a diagnostic OBD2 scanner. Repair any codes that may appear.
A scanner can test the operation of the fan circuit by commanding the relay on and off through internal test parameters.
The PCM controls the electro-viscous fan clutch engagement. The PCM regulates a 12-volt pulse width modulated signal to the cooling fan relay. The signal determines the ON time of the relay. As the commanded state of the fan clutch increases so does the ON time of the relay. This ON time directly affects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.
The fan relay is in the power center under the hood. It is relay number 3. Also check fuse number 20 (10 amp) with a test light to see if it is blown.
IMPORTANT: Installation of the proper relay is critical. If an enhanced relay equipped with a diode is installed into a position requiring a standard relay equipped without a diode; excessive current will damage any components associated with the relay or its associated circuits.
Last edited by TechHelp2 (1/11/2010 4:39 PM)
Sometimes my engine sounds as if it is over speeding but the tact show not so.I believe the cooling fan is engaging but I have no indicating lights going on.It last a few minutes and then the engine becomes quiet. When this does happen it sounds like a big truck just starting out in first gear pulling a big load. Thanks for taking time to answer my question.
I don't know what year truck you have but if it is a later year truck the fan is controlled by the PCM and from how you are describing the operation of the fan you have it appears that the operation is normal.
I would need to know the exact year, model, engine size and any information you can give to be certain the operation is normal.
Depending on the year a mechanic can put a scanner on the truck to see if any trouble codes are stored in the computer memory and he can also command the fan to go on from the scanner to confirm proper operation.
As long as the fan is operating it doesn't appear you have anything to worry about. If you are using the A/C; the fan clutch will be more active depending on the demand for cooling.
If you are still concerned about the fan then get me the information I requested and I can look into the matter further.
There is a post I entered a while back on the operation of the fan on later models. If you can't find it I can repost it for you.
Get back to me when you can.