could that decrease my gas mileage?

It makes a noise and definitely needs to be replaced. Everytime it kicks on it vibrates and makes a bad noise. Recently turned my heat cause it is slightly warmer and seems to be much better.

 

I would unplug the wire to the compressor and see if the noise goes away.
If it doesn't go away, it's probably the clutch bearing. If it goes away, I would leave it unhooked til you can get it replaced. If it (either clutch bearing or compressor) goes out completely you'll have to have it towed and it'll most likely cost you a belt also, maybe more.

 

Sounds like a bad clutch plate and/or pulley (bearing).

 

it only vibrates when it is cold, then about every 5 seconds it sounds like a switch kicks on in my dash and the odd noise starts. I took it to a mechanic and he showed me it was the compressor....you could see it when you popped he hood. It would kick on and everytime it would make the noise. Curious is this could drain my fuel?????

recently had a battery change and the noise was much louder before the battery change.

 

Can't imagine why a battery change would have ANYTHING to do with the noise the compressor made. Where do you live that you run A/C this time of year? Read my post above.

 

I recently changed my AC compressor and my noise would go away when the clutch engaged. I saw no difference in MPG, but I did change it before it completely locked up nd left me stranded with a messed up serpentine.

 

Let me explain a little better since I am no all that auto savvy. I live in Lexington, KY

For about 1 year my truck has made a vibrating sound and it ONLY when my heat or ac are on. I took it by a local mechanic and we popped he hood. Whatever it was(he said compressor) would be quiet when it was on moving the it made the noise when it would activate. It would kick on and off. You would have to replace it from the bottom of the truck and if you looked down through the engine it was just to left of midline. He told me that as long as the noise was not bothering me, to leave it be.

Recently it became much louder...to the point that I would turn the heat off on the way to work cause it was so annoying. Around the same time I noticed my truck was having a hard time turning over from cold. Come to find out my battery needed to be replaced. Since I have replaced it, the sound is quieter but still there.

Also I had severely decreased gas mileage(loss of 35mpg) and the last tank finally got back to normal, but had the heat off for most of the tank. I didn't think the heater would drain the gas as much as the AC, so I wonder if it is the bad compressor. Grasping for straws.

 

You can replace just the clutch. That way you will not have to recharge the AC.
That is what I did when the clutch bearing went out. It cost me less than 100 bucks and and hour or so lying under my truck.

 

I will repeat what I've already said. I know of absolutely nothing that would connect the battery and the compressor noise at all. Even if the battery was failing and didn't supply enough juice to the clutch, the alternator supplies the juice for pretty much everything when the engine is running anyway. The battery just creates a steady flow path from the alternator to whatever is asking for the juice. Your compressor shouldn't be running when the heat is on I don't think. When the defrost is on yes, but not with the heat. It is normal for it to cycle on and off pretty frequently, ESPECIALLY this time of year. If the charge is getting low, it will cycle even more frequently than usual. As I said, DISCONNECT the wire to the compressor, as long as the system will function that way. Some of the newer vehicles are programmed to shut the whole system down when it recognizes that the compressor isn't working. As said before, ignore the mechanics advice. If it is making enough noise to bother you, sooner or later you're going to have to get your Auto Club card out, because you're gonna need a tow!

 

Maybe it does need a charge. It does kick on and off every 5 sec and last summer I had it charged and the sound went away for a while.

someone suggested above to replace the clutch....would this solve the problem.

 

If the AC compressor is starting to seize when it engages it will put a strain on the engine. The compressor is engaged by the compressor clutch pulley. The pulley could also be at fault. If its bearing is going out it will also put a strain on the engine. The Vent, Floor and Off positions are the only settings that will not engage the compressor. Unplug the pulley connector and see if the noise stops. If it doesn't the pulley is most likely the culprit. I would still take the truck to a competent AC shop for a proper once over the system. They will properly test every component and recommend the proper repair.

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What truck are you driving that the compressor works with the heat on?

 

Ford runs it when you have the defrost on to dehumidify even if you have it on the hot setting.

If your compressor is good but the clutch is seizing or broken you can replace just the clutch and it will fix your problem. Unplug the clutch power and see what happens.

 

Most Fords run the compressor in ALL settings except VENT, HEAT (floor-only) and OFF.

Consult owner's manual for specifics.

 

I'd just head to the junk yard and pick up a used one. Throw it on. Recharge it myself (easy).