Compressor On & Off, 140lb running pressure! Help

[xploder98]

Ok guys, definately need some help on this one. Just put in a freshly rebuilt engine and now when I turn on the AC the compressor turns on for 3-4 seconds and shuts off for 4-5 seconds and over and over again. And when it turns on it sounds very irregular, too much pressure. If I'm in gear (any gear, this is a manual trans) and turn it on it puts a heavy heavy strain on the motor, as if I'm slappin the brake hard and stompin on the gas (compressor turning on & off). Today I checked the running pressure and when the compressor was on it was at 140lbs! When it shut off it dropped to 120 or so. I shut the AC completely off and checked it and it was at 200+lbs! Is this a clogged orphice? Please let me know, I live in SoCal and its about 110 daily. Thanks for the help.

 

[NWExplorer97]

A?C issue

1 - If you have a set of guages & you're sure the system is fully charged; Does the low side pressure drop down into or near a vacume? This would definitly indicate a restriction most likely at the orfice tube. I just had to replace mine 1 a month ago, without warning.

2 - Is the radiator clutch fan engaged and is there an electric fan coming on?
In 110' temps the high pressure would increase rapidly without either of these working?

3 - You could also having a compressor going bad, but this is less likely then the orfice tube. Here's what usually causes an orfice tube to become restricted. In the Accumulator (Filter/Drier) there is a desicant bag, overtime they deteriate, even sooner if moisture enters the system and the desicant travels thru the system and builts up on the orfice tube. When replacing the orfice tube ($12+/-) be sure to replace the Accumulator ($50+/-) It's advised you also have the system flushed out, if you're lucky (like I've been) you may get by without doing the flush.
Of course the system needs to be drained to replace parts and recharged.

Their is a special tool for removing the orfice tube, however sometimes even with the tool the tube is stubborn and wont come out, You can then try a small long needle nose plier or hemostat type tweezer. Last resort a long wood type screw, screwed into the tube & then pulled on to remove the tube.

Hope this helps, let me know if you need further help. I'm a semi-retired ASE Tech & I was a Voc-Tech School Instructor specializing in A/C.

NWExplorer97

 

[NWExplorer97]

A/C Issue

If you don't have guages, you can disconnect the low pressure/cycling switch mounted on the Accumulator. Take a wire or paper clip and jump the 2wires. The compressor should engage and stay engaged,the system should get cold within 1-2 minutes, if not cold you may be low on R-134. Also place your hand at the orfice tube, usually if there's a restriction you can sense a build up of heat from the friction. I've done this for over 20 years and know what it feels like, you may not if it's the 1st time you tried it.

 

[xploder98]

I'm just using the simple 134A refill kit guage on the charging port and getting those pressure readings. Idk about jumpin the wires. If the compressor keeps shutting itself off I assume its for a reason (pressure). I'm not 100% sure the refridgerant is fully charged, but I can't charge it with that much pressure in the system. I went to let a lil pressure out and it damn near shot the nail out of my hand from the 200+ lbs of air. So where should I start? Should I replace the orifice tube, the accumulator and flush the system?

 

[NWExplorer97]

A/C Issue

If the system was empty it has to be drawn down into a vacume prior to charging, otherwise the air in the system will increase the pressure and the system will never perform properly. Adding by hand with a can is only to be done if the system is low and needs topping off.

By jumping the low prssure cycling switch the compressor should stay engaged (not on & off) allowing all the R-134 from the can to be pulled into the system. If the pressure gets to high the high pressure switch should still turn the compressor off for safety.

If you're still having problems, draining the system & removing the orfice tube is the only way to confirm whether it's restricted. It should look obvious, with the fine mesh screen clogged up with caked on debri (usually the desicant, if there's metal "glitter" then it's from the compressor).

 

[xploder98]

I understand. The problem Im having is when I go to charge it the pressure reads 140 (on the low side) which is too much to try to charge it. I think I'm just gonna replace compressor, accumulator & orifice tube and vaccum the system and charge it. Then see what happens. Sound good?

 

[NWExplorer97]

A/C Issue

That should take care of it, it doesn't leave much else to be at fault. You should learn alot by examining the orfice tube (as privously mentioned).
Good Luck