Hi. Last November I had my A/C Comp. replaced (went w/a rebuilt one on ebay) because the clutch/pully was almost falling off and my local mechanic suggested replacing the whole thing instead of just the clutch assy. (1st miss-steak) The day I picked up my truck & put the A/C on it seemed cool, but not cold, but it was cold outside (Nov. in New England) I thought I'd see how it is when summer hits. (2nd misteak) Well, now the thing isn't cooling much at all. Maybe 48 ' F reading with a thermometer in the center vent.
Brought it back to the mechanic. Put guages on it & said the suction side could be better/higher. He added a little freon and no change - so he ruled out low/leak in the freon.
He thinks the rebuilt compressor I got isn't as good as the one that came out. Is that possible? I thought either they worked or didn't work.
One thing I need to mention, is B4 the job, my old compressor would frost the windows - it was like a meat locker in the cab. Now, if at night, or parked in the shade, it might get cool, but no blue knuckles (my right hand on the steering wheel right in front of the vent) when I'm driving.
The Blue guage read 25lbs and he said it should be around 30 and maybe there was some sort of a blockage. I'm not sure, but I thing the high side was 200 or so. Would sucking (evacuating) the freon again & refilling it remove a potential blockage?
Did he replace the orface tube and dryer assembly when changing the compressor? Did he pull a good vacuum on the system before charging it? Moisture in the system will freeze and cause problems in not properly vacuumed down.
Don't know about the orafice tube, unless it is connected to the dryer.
He did replace the dryer and said he had a vacuum on the system for an hour.
He said an hour was the usual time he leaves them on.
The orifice tube is usually connected to the evaporator, where it meters (filters) the Freon into the evaporator. I wouldn't suspect trouble w/it b/c your old compressor did not fail internally. However, if it were clogged by debris it could show a falsely high pressure & not cool to low temp.
Given that nearly 8 months have passed & we see a high number of complaints about blend door & control knob problems here, perhaps the AC is not at fault? Check the temp in the PANEL position-heat off, to be sure you're getting ambient temp, not heated air.
I haven't had problems w/F134 yet or memorized pressures, but "200 or so" would be marginal for F12. On F12 systems you'd expect "high side" pressure in the 275-300 range.
Finally, an AC should cool in the 40-50 degree range, making "Maybe 48" about right. Conversely "my old compressor would frost the windows" sounds like a fault. These systems were not intended to perform as freezers & when properly adjusted should not "frost the windows". If they did the evaporator would quickly ice over externally, blocking air from passing through, b/c condensation would freeze instead of drip away. The compressor should cycle to avoid freezing up the evaporator.
It sounds like the evaporator is starving for liquid. With low suction and elevated supply air it may be: Low on charge,Partially restricted orifice,or a restricted drier.
"Conversely "my old compressor would frost the windows" sounds like a fault. These systems were not intended to perform as freezers & when properly adjusted should not "frost the windows."
I was only kidding - but yet trying to explain that no matter how hot it was outside, if I put the A/C on, the cabin would always be cool in less than 15 minutes - to the point where I'd eventually have to turn it off or at least down (actually raising the temp) or crack a window or something.
On my way into work tonight, outside air temp in the low 70's and very high humidity, if I had to guess, I'd say that the temp blowing out of the vents was around 35' F. Almost too cold to leave your hand in front of the vent for an extended period of time. But it seems that when it's hot outside and the truck is in the sun, it just can't get cool - no matter how long (45 min) the engine is running and whether you're on the highway or not.
Assuming the system is vac'd properly and the other points already made - 200 is low for 134A. The high side pressure will vary with air flow over the condenser. Esp on hotter days. The outside temp and air flow both need to be factored for hs pressure. But idling with engine warm and cooling fan engaged should be up closer to 230-250. I would not go over 270. Or 40 on the low side. Best to have an external fan blowing into the grill while testing.
will have to dig up a temp chart on 134a high side. 134a low side actually runs higher than r12. i have seen 500 on a properly working gm system. but because of no air flow. 250-270 is around my usual pressures to get cool. higher will strain the comp and will show in mpg.
My CD manual says high pressure side of the compressor should 300 psi maximum at 100 F and 180 psi minimum at that same temperature. Low pressure should be in the range of 20 - 45 psi.
__________________
John
aka KingRanchMan02
`02 F-150 King Ranch SuperCab
Charcoal Blue/Arizona Biege
5.4L 3.55 LS, 4x2
Diablosport Predator Programmer, K&N filter.
`08 Sable Premier
Merlot Metallic, Black leather
3.5L Duratec, 6 speed automatic
Another thing you have to do when replacing a Vehicle AC compressor. Take the old compressor and drain all the oil out over a glass measuring cup, note amount of oil and properly dispose of old oil. Take new compreesor and pour out oil, in clean glass measuring cup. Only put back in the compresor, the amount of oil you measured in the old compressor. Also you should treat the accummilator the same. If you flush the system pour the oil out and put back in what Vehicle specs call for. Also when pulling a vacuum you need a micron gauge to tiel if the system is tight, "no leaks." Just pulling a vacuum for an hour with leaks can pull non -condensables into the system, and give poor performance.
