To evacuate or not to evacuate A/C

[jeffbeck]

I had a leak in my condenser, so I replaced it myself. I first added 2oz of oil and then put in a can and a half of 134. It blew cold for that day, I don't seem to have any leaks, but then the next day. same old thing, blowing warm, and the clutch isn't turning with the A/C on. I did not evacuate the system before charging. Was that truly an important step?
I know that prior to changing the condensor, all the 134 would leak out within minutes... now if I push in the little pin on the low hose, there's plenty of air in there... I know the compressor is ok cause if I jump the cycle switch it go on and stay on. Could it be anything to do with cycle switch? I'm stumped, and don't really want to spend too much money on this.... got the condensor off ebay for $15.00 and spent another $30 in refrigerant and oil....

[craig campbell]

If you break the system open, you need to vacuum it to remove moisture, etc. Also, by pulling about 29 inches of vacuum for a while, it shows you don't still have other leaks in the system. My guess is that there's still a leak somewhere. I guess you can bypass to make the compressor engage, but I don't think that would prove there's no leak from the compressor. You could try using a dye to see if you can spot any more leaks. Also, Jeep evaporators (under the dash) are supposed to be prone to developing leaks. I had a confirmed evaporator leak (along w/ $800 quote), but fixed it w/ a two part metal and rubber seal kit from Wal-mart. Air's been fine for a couple of months now. Good luck.

[jeffbeck]

If it is in the evaporator, would a "PepBoys" be able to determine that without pulling the dash apart?
how did you apply this 2 part seal?
does the evaporator typically leak in the same spot? (ex. at the hose connection) or it could be pretty much anywhere?

[craig campbell]

Any place that can do AC work can put dye in the system and I guess they must assume it's the evaporator if the system leaks and the dye doesn't show up on any of the joints, parts or hoses out in the engine bay. I didn't see what they did to diagnose my evaporator failure (vehicle left at shop), but I'm sure they don't get under the dash because it's a bear of a job. I heard another post implying that evaporator leak diagnosis is a deduction for that reason. I think it's worth getting a shop to do the dye and come up with a diagnosis... but I suspect you can find dye kits at Wal-mart and car parts stores... I've just never done it. Most of my leaks, except this one, were really obvious and always the compressor front bearing. The stop leak kit I used cost about $11 and has a can of sealer for metal then a second can to flush the metal sealer and seal rubber. You'll probably need a large and a small can of 134a (I've forgotten the sizes I used) to get the right pressure on the low side of the system and the large can I got had a guage on it... just fill 'til you get 45# and icy air. I had only added the large can at first and it sort of worked but not that well (guage was reading about 25#) and compressor was cycling alot. I'm still sure you need to vacuum your system and the AC place could do this for you. I'm amazed the Wal-mart stuff worked, but for $35-40 vs $800 or me ripping out the dash myself (I actually started to)... I figured it was worth a try. I'm not sure that stop leaks can't damage the system, but this is a spare car for us so the downside isn't so bad... we're just taking it one summer at a time.

[dksob81]

you probably don't have enough pressure in the lines. when I first got my jeep my A/C didn't work and I noticed the clutch would only spin for about 2 seconds then stop for a few seconds then on, etc etc.. I added more freone til it stayed on and watched the guage on the can made sure it wasn't in the red, and it works fines now.