Topic: Noticeable performance decrease with AC on ?

[Alexxn 00 Si]

Hey guys, while I do know that having the A/C on kills some power should it be that noticeable ? Lately it seems that with the A/C on I am having the engine surging. At constant speed on the highway I can especially feel it. Also when taking off from a stop, my Blazer accelerates steadily but I can feel dead spots and then it picks up again.

There isn't any noise coming from the compressor when it's on, BUT with the engine off if I try and turn it by hand I almost can't turn it at all. Very tight.

Any ideas guys ????

Thanks !

[Rick Norwood]

I assume that the A/C works (Cools) properly. You might check for vacuum leaks espescially in the dash A/C control switch. But, I don't think the power loss should be that noticible.

[Alexxn 00 Si]

Yep A/C freezes you out of the truck...I just didn't know if the compressor should feel that tight or not, but I would assume that if it is freezing up or something there would be a noise or it wouldn't cool or something....

[Mikado14]

First off, what year is the vehicle?

I will assume that you are talking about a Blazer with vacuum controls. What Rick Norwood said is more than likely your problem.

The selctor lever on the right of the control panel, has a vacuum selector switch. This switch has silicone on it for lubrication. Overtime it dries up and deteriorates.

A way to check it is to run the vehicle for about 30 seconds. While it is running, set the selector to AC. Shut the engine off and listen at the controls. If there is a vacuum leak, you should be able to hear it.

I have had to change 2 of these in the past 3 years for that problem.

[Alexxn 00 Si]

Blazer is a 2000. Yup tried doing that, nice and quiet. Truck idles fine with the A/C on too.

[BlazerLT]

I would have the AC system checked for a low refrigerant level. The compressor will cycle like that when the refrigerant is low.

Also, maybe time for a tuneup.

[slammed s10 87]

Originally Posted by BlazerLT

I would have the AC system checked for a low refrigerant level. The compressor will cycle like that when the refrigerant is low.

Also, maybe time for a tuneup.

does the a/c system have enought pag oil in it?

[Trail Blazin96]

The compressor is a pump for the refrigerant so of course it will be under pressure, and you wont be able to turn it all the way.

[Mikado14]

By chance, did you recharge this with a can from a store?

An overcharged system will make the compressor work harder, equate that to more load on the engine. Further, if you run an overcharged system, you run the risk of damage to the compressor. If liguid enters the suction side (large hose) that is a big no no, it will ruin the compressor. That is the purpose of the accumulator or receiver/dryer, to capture any liguid prior to going to the compressor. That is why it sits vertical.

An overcharged system will cycle quickly. High side will definately go over 200 and quite possibly to 300.

When the compressor cutsout at the low setting, the high will drop and the low will rise. Depending on the size of the system, it should kick in at 60 and the cycle starts all over. This is normal. The switch on the accumulator controls both the cutin and cutoff.

If the system is overcharged, liguid in the suction expands to a gas quickly and the compressor pulls it quite rapidly and could pull liquid in on the suction where there should be only gas.

It is impossible to tell you cycle times without a plethora of specifics, but cycle times decrease with the greater the charge.

However, ambient temp and humidity are also factors.

Now, if the engine surges with the A/C on, I would check the IAC. The ECM will compensate to maintain the idle with the additional load of the compressor.

If your driving and you are getting a noticeable change, the compressor might be going bad and should be checked by someone who can tell.

Remember, you don't want to seize it for you will lose your belt and you'll need the hook to get you home.