Be prepared for a long story. I have a 99 jimmy that has a freon leak. I put dye in and found it all over the belly of the compressor and the clutch. I'm saving money to buy the parts, then I'm going to get the system evacuated and flushed then return to the shop after I install the parts for a system charge. In the meantime, I was adding some 134a to it and noticed a lot of bouncing in the belt tensioner. I didn't think much of it at the time (yesterday).

Today I'm heading to work (2nd shift) and was costing down hill and noticed my RPM drop from 1000 to about 500. I was giving it a little gas but not much and I had the AC on high (96 today!) It did this a few times.

So my question is: is this because of the compressor or the belt tensioner? I also had the tranny rebuilt about 2 months ago but I don't think it has anything to do with it. Its been runing great and I actually gained almost 1 MPG after the rebuild. Any ideas are greatly appreciated!

 

Could just be a tight compressor and needs a little break in time. Or it could be a marginal belt tensioner, but that alone will not cause RPM to drop.

Any one or more of several things can cause high side pressure to rise and bog down the compressor:

High ambient temperature, (which you have at 96F).

Poor air flow across the radiator and or condenser due to debris stuck in the cooling fins.

An overcharged system, (too much refrigerant and or oil).

A faulty fan clutch.

Partially restricted FOT, (fixed orifice tube) or any restriction in the high side.

 

Thanks as always captain! I haven't actually changed any parts in the ac system yet. Gonna have the new compressor on Friday, then I'm gonna tear into it. After the evac and flush of course. Hopefully the new parts will take care of it. I may go ahead and change the tensioner as well.

 

Pull the FOT out and check it for metal debris. That's the first thing, (after the condenser) that will catch stuff if / when the compressor takes a dump. If the FOT is torn, there's a good chance metal debris is in the evaporator. It's almost impossible to flush the condenser and evaporator due to the way they're designed and built. If you don't replace them, flush them best as you can and put a filter in the suction line just before the compressor. If the FOT is not torn, chances are pretty good there's no debris in the evaporator. It is impossible to flush the accumulator so you have to replace that.

 

Thanks for the advice captain! I'm going to replace the FOT with an adjusting one. You definetly know what you are talking about and if you say they work I trust you lol.

 

Oh yes, they work! There are two different ones available. One is for ambients above 105F and one below 105F. In Iowa you'll need the one below 105F. Ambient temperature increases pressure, and if you put the 105 + in there, it may not get cold enough when ambient get down in the 70's & 80's.