A/C Problems

I have a 90 cherokee and I have just converted the A/C over to R-134. I know that it isnt going to be as cold as R-12, but it should be a lot colder than it is. I have a couple of problems. First, the A/C doesnt blow very cold through the vents, but when checked, the system is at full charge. It does not have any leaks. I have not changed anything on the truck other than the freon. The system was never open for any length of time. My uncle was the previous owner and tells me that it had a very slow leak. I have not had any drop in pressure in the system now for 3 months. Is there something else I need to change to make the R-134 work correctly. Second, the air coming out of the vents takes along time to get going. It doesnt matter if it is High, Normal, or Bi-Level, it all takes a good 3-5 minutes to get going. It will blow out of the defroster vent immediately, but the rest take a while. When I use the heater, the air comes out immediately, no problems. I am knew to owning Jeeps and I am not yet familiar with the workings of the Chrysler way. I have been working with cars for at least 8 years now, but they have all been 65 - 72 chevelles. Any and all suggestions would be greatly appreciated. Thanks guys.

Air that comes out of the defroster vents onlyis a sign of a vacuum leak that is allowing the air plenum doors to stay in their default position, which is "defrost".

I would check for sufficient vacuum first. A common problem on XJ's is th cracking of the vacuum reservoir, located inside the bumper on the right corner, usually. Another problem on older XJ's is the vacuum line from this reservoir runs UNDER the battery tray, where battery acid and corrode the rubber and cause a leak.

Important question: when you changed your AC system from R12 to R134, exactly what steps did you take? At a minimum, it is recommended to flush the system of R12, change the oil in the compressor (oil used with R134 is NOT compatible with that used in R12), and replace the receiver/dryer.

Did you do all this?

Make sure your compressor clutch is actualy kicking in...

When I did mine the expansion valve, "H" block, on the firewall needed to be changed to a 134 valve. Also the drier should be changed. It acts like the filter for the system and can collect alot of gunk. And like AZ Jeff said the system needs flushed good.
Keith

Thanks Everybody

Guys, I just want to say thanks to all of you for your help. I will definitely be taking all of your suggestions into consideration when I try to fix my A/C. I am gald I was fartin' around on the internet and found this site. I have learned more about my Cherokee since reading this forum the last couple of days than I have in the 6 months that I have owned it.

One more question? How do I flush the system? Is this something I can do on my own, or do I need to take it in?

Again, Thanks for all your help.

Keep on keepin' on.

Flushing, done properly, requires that the system be opened and a special flushing agent be run thru the lines, evaporator and condensor. Then, the system must be fully evacuated with a vacuum pump, and refilled.

To properly flush the system, the existing refrigerant should be captured, not just vented into the atmosphere.

Unless you have an AC manifold and guage system, and a vacuum pump, recovering and recharging AC systems properly is pretty much impossible.