Going to try and break this down. My AC blows cool while driving on the highway. When I say cool it was 90deg this morning and it was around 74deg coming out of the front vents on the highway doing 70mph. The back AC vents never did cool down. When stopped only warm air. When it reaches over 101deg no cool air at all on the highway it stays warm. I am guessing the pressure has gotten too high to cycle the compressor?

I am lost as to where to start. I don't have unlimited funds as I am out due to back surgery a month ago and can't return to work for another 6wks. 🙄

I appreciate any assistance.
Tom

 

First thing to check is if the compressor is turning or if it's constantly cycling on and off.

 

I can see it turn but doesn't run for long. I put some gauges on it but had no clue what I was looking for. The low sides seemed high while the high side was low.

When I turn the AC on it feels like it makes my truck run a little rough. No cylinder misfires.
Tom

 

Tell us what the numbers were, both when the compressor is off and then when the compressor is turning.

 

I will grab a set of gauges tomorrow and check the numbers.

 

This was the reading in pretty much all settings of the AC unit in my Expedition. The high side barely moved when pushing on accelerator.


I ended up bleeding pressure off the low side to around 30psi. While doing so no freon came out just gas. Less than 3ml came out.

 

The gauges, if set up properly, tell me the compressor isn't running or, at least, isn't doing anything.

 

It was turning.

 

Then it wasn't doing anything. The compressor simply isn't doing any work although to your eye it appears to be running.

When the clutch is off, the pressure should equalize to the static pressure determined by the underhood temperature. 130 psi equates to around 100F.

When the compressor clutch engages and the center shaft actually rotates (CHECK IT) and the compressor operates, the low side gauge should drop and the high side should rise as the compressor creates a pressure differential. It is possible for the clutch to engage but the clutch has failed causing the shaft to remain stationary. You have to make complete observations once you know what to look for.

If there is no differential created, it's usually due to either an internally sheared compressor shaft or the internal valves have failed.

 

It was about 90-95 degrees out with 35% humidity. So what about just pulling off the gas when I bled it and maybe only 2ml of freon came out. This was when I bled the low side.

Bottom line it for me. New compressor? I appreciate your time and assistance.
Tom

 

Like projectSHO89 said, you need to make double sure the CENTER of the compressor is turning and not just the pulley, before anyone can advise you further.

 

pretty much, if the gauges are set up right AND the compressor is working (Center part turning), the internals of the compressor is shot. you will have to replace, at the least, the compressor, expansion tube and accumulator. I would also, with the age of the vehicle, the condenser as well just to remove that variable as well.

rock auto is your friend.

D

 

Crap that got expensive. 😆 I appreciate the information and will be riding out the heatwave.

 

that's static pressure: same between low and high side. When the compressor is running it should around what my chart I am attaching says

 

It CAN'T be turning! Pressures are never the same high and low side when its running, no matter if the compressor is bad or not, there is always some variation.