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1999 Blazer AC

When using my AC on the highway everything is fine. However, when I come into town and continue in stop and go traffic the engine noise is extreme. I am told it is a fan for cooling. It is so loud that sometimes we cannot hear each other in the car. Besides the noise I lose power and the transmission shifts really hard especially between 1st and 2nd. I have had the radiator boiled out and 2 new fan clutches installed. Nothing has solved the problem. Help!

Have you opened the hood and looked at the fan?

No! I have no idea what I would be looking for. I was told that there is one fan that just spins faster because the radiator is to small. It is the sound of the faster spinning fan that causes the noise. It was originally thought that the clutch was not letting it switch completely to the faster speed. I have contacted Chevrolet and they said they had not heard of the problem. I know of three Blazers in my small town that have the problem.

I could direct you to a technical Service Bulletin (TSB) about fan noise if you wish.
Your problem is complicated by a percieved lack of power and a percieved shifting problem.

We had many S-Blazer (as your SUV is known as) customers come in and complain exactly as you, noise (a roar) percieved lack of power (none discovered) and percieved harsh shift (none discovered). It was all due to fan clutch operation.

I have been told that the harsh shifting is because the transmission has become hot. As soon as I have driven a while without the AC on or stopped and let the car cool, everything is back to normal. I live in Calif. and the temps are over 100 many days so the AC is a must. I am surprised that you have a Service Bulletin concerning this as the local dealer says he has not heard of the problem. As I have previously stated the fan clutch has been replaced twice. In the cases you talk about (oldschool) does changing the fan clutch solve the problem of the noise?

See if refering your mechanic to this bulliten helps 99-07-30-016b

I would like to paste the rather lenghtly bulletin but it seems to be copyrighted

If not copyrighted I am having trouble pasting.

Thanks! I let him know and see what happens.

I know this is a stretch, but I’m wondering if the problem is actually in the AC system. If the compressor is bindng it could be loadng down the engine as well as making noise. That could allow for both the noise and the power loss.

Upi have a third factor here, and that’s the tranny problem. It sounds like the tranny is overheating. The tranny also cools through a radiator of its own, which is either built into the main radiator or stacked over it (I’m unsure of your setup). If that’s disspating too much heat it could be affecting the ability of your engine to dissipate its own heat and causing high idle.

It could also be a combination of both of these problems.

Again, I’m thinking “outside the box” trying to tie the problems together. As always, I welcome the feedback of others on these ideas, even if they prove that I’m “all wet”. The idea here is to help the OP, not to protect my fragile ego.

Thanks I’ll have these ideas checked. You mentioned that the heating of the tranny could cause the high idle. That is not a problem----I have not been aware of a fast idle at any time.