the a/c on my 01 v6 hasnt worked correctly all summer, the floor vents work fine but the other four vents only blow air occasionaly and for only a short while (~30sec). when i turn on the heat the vents blow normally. My a/c compresser cycles on and off about every 10sec and i was wondering if this was normal or if this could be the problem as i have already changed the freon and vent motor.

 

I give up on trying to fix one of ours. Gonna bite the big one and pay someone to get it right. Replaced the compressor myself and had it charged by a certified A/C person. It blew cold for about a week and then nothing. Compressor still works but he said we had some kind of blockage in the line the night he refilled it.

 

You will need to get a set of gages hook up to your system. The most common cause of the compressore kicking on and off is low pressure due to low coolant. But there is also high pressure switch and you need to be absolutly sure your not bouncing off the high side before you try to add coolant.

 

99% of al AC blockages end up being in the orifice tube. The orifice tube is the very small opening where high pressure becomes low pressure, so it makes sense anything in your system would get stuck there. If the blockage is someplace else that place should get very cold unless it is completely blocked.

So whats blocking it up? Assuming the system was not run on the open road while a hose was disconnected there are 3 possiblilty. The most common is metal left by the old compressors. If a compressor fails due to a leak the system does not normally need flushed. If a compressor seize or "get loud" then you should flush the system. If it is a car I just bought I will pull the orifice tube and check for metal. If there is any metal then the system will need flushed.

Second black stuff from the dyer receiver. This would mean the silcon bag broke and you need to get all that cleaned up.

Third would be if at some point someone put an incompatible oil in the system and it reacted to the existing oil and sludged up the system. This normally show up as very poor operations but it can make a system non functional.

 

The original compressor did not fail, we just broke the wiring connector off it when swapping the engine. I added the oil called for on the side of the new compressor. I did not flush the system. When the A/C guy pulled a vac on the system. It held the vac for a pretty good while, not sure how long but awhile. He added the freon and the system began to cool. The line running from the firewall to the condensor is the line he says has a block. About 6 or 8 inches of the line coming out of the firewall is cold then it turns hot. After about a week, all the lines are hot to the touch. I don't know if it leaked out or if it is totally blocked at this point. Oh, and we did leave the system open while we were swapping the engine. Sorry, don't mean to highjack thread.

 

Checking for leaks using the Vacuum is not a great way to do it because of the low pressure involved. For simple rounding purposes you can sau that for every 2 inch of vacuum you are talking 1 PSI. If you pull the system down to 25 inchs of vacuum that a little over 12 PSI of rev pressure. Are you say the mechainc told you right away there was a plugged line? Your oil did not have enough time to gell up so it is either metal or that black crap.

 

Yes, after about 7 or 8 minutes of it cooling, he held his hand on the metal tube where the cool became hot and said it had a blockage in the line. He pulled the system down to 25 inches and let it sit for a while before charging it. He told me he thought that the line had a filter in it where he thinks it is blocked. I am just going on what he told me.

 

are you getting cold air and its not going to the right places?

 

the air comming from the floor vents is cold but the other vents dont blow. about every 10 mins the vents will blow cold air for lik 30seconds and then stop again.