Hi All,
I have Envoy 2006, since two weeks I have been noticing the following problems

- Fan speed fluctuating
- Tachometer fluctuating, on Neutral & Drive. when car stops at the signal for example, either transmission is put on Drive with break or put on Neutral the rpm shows this fluctuation.

anyone can help or has any advice !!!!

Thanks

I had an '02 blazer with the inline 6 and my RPM's fluctuated at start up but I don't believe my clutch fan would fluctuate with the engine. My problem was corrected by replacing the sensor on the upper front of the engine....I wish I could remember exactly which sensor it was but I can't recall. I know it was upfront and easy to access and once replaced my engine did not over rev on start up. Luckily for me the SES light would come and go which gave me the clue to what sensor it was.
Good luck!

I experienced this issue yesterday for the first time (2003 Vue 4 cyl. AWD). The only think I can think of is that I replaced the battery (Duralast) earlier in the day, but it's just a battery--nothing too complicated. It was about 20 degrees out at the time, but the issue went away a few miles down the road (so I don't think it's necessarily outside temp related).

The first time I started the car today, turning on the fan did not make the RPM's fluctuate between 200-800. However, later in the morning, I started the car, turned on the fan and BAM! the engine was bogging heavily. I tured the fan off, because there was no way I was going to drive it like that. About a mile down the road, I tried the fan again and it worked as expected--no issues.

The issue happened in any of the directional settings (defrost, defrost/feet, feet, face, etc.). I've not tested the issue with the temp set to cool.

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