Air Conditioning Problems

[LS431o28]

Well im a little AC/R literate and im having a probelm that just wont go away. this is what i have 91 Ex XLT 4x4. the air was changed over to R-134a in 1998 and it hasnt really worked since than. I picked up a leak detector a while ago and found two areas that might have leaks ( think the detector was bad) anyways i picked up some of the R-134a Leak detector/Sealer and put it in than charged with one 12oz can. so right now im getting pressures of L25 H225 at idle. Ive done some messing at different RPMs and its
1000 - 30 -- 260
1500 - 23 -- 270
2000 - 26 -- 318
2500 - 23 -- 305
Nothing seems to stay consistent at one point I noticed the High side shot up to about 450 (bout crapped my pants) but i couldnt get it to duplicate that again. I thought maybe a chink of something had lodged itself in the high side but what ever it was only happened once. anyways is there anyone out there with some info i can look at or can help me with this dilemna.

Thanks:redexp:

 

[bippy93]

It sounds like you either have a restriction, like
maybe the orifice, or the system is overcharged.
Both can cause high pressures like you have.I
would need more info to help much further.

 

[mrboyle]

I agree, it sounds like you have a plugged orifice tube.

 

[Texan01]

you got it overcharged. I did the conversion on my 6000 and blew the safety valve once and about 4 compressors before I figured it out. I eventually found out it needed to be running at 2500rpm with a garden hose running over the condenser to get the proper charge in it. I wound up with 2 cans of 134 to get it right.

You also need to adjust the low pressure cycling switch or you'll burn up the clutch. you need to bring the low side down to around 20psi

Check the orifice also for restrictions but your head pressure is waay too high.

That said your pressures should be around 20-25 low side and 180-210 high side at 2000 rpm.

I've got a page full of useful info about it but since my computer is 140 miles away at the moment. I'll post it tomorrow

 

[LS431o28]

well ivegot alot more info as to what ive done just didnt want to overload the page. when i first got started with this I had originally placed to of the 12 oz cans in per some book i saw when the system is drained. i added the oil and than the two cans kept an eye on it for several days and the system eventaully drained again. i used the leak detector. and noticed to places it could be possibly leaking and just said the heck with it. well the last couple days have been HOT here so i decided to try again this time i got the leak detector/sealer its about a 6 oz can i think went to start the AC and the clutch wasnt cyling due to to low of a pressure. manually jumping the switch it tarted and began to filll the system with the leak sealer. than i added the 12oz can of 134a and decided to let the system settle out and adjust i recorded all the readings (above) and things just didint look right. so before i add anything else i thought id ask here for some info to better clarify things. I wouldnt think that just the leak sealer and a 12oz can would overcharge it, but than again i have no idea how much was in there and hadnt actually leaked out. well thats about all that i have done. hope this provides some better info for you all.

Oh thanks for all the replies I really appreciate them :redexp:

 

[LS431o28]

cant remember off the top of my head but would an overcharge act like an undercharge where the air coming out is cool but not cold. the outside air is about 90 and the air coming out of the vent is about 67. Im really getting anxious to get this working i think i can cook eggs on the roof of the X now.

 

[bippy93]

I think the system only holds just less than 2 cans
of R134a, so if you are not sure how much you started
with, it may very well be overcharged. I would start
with an empty system and take it from there. Also
if you are converting an R12 system over, it may not
blow as cold with the 134. I think the Ford conversion
actually has a new condensor in it, but I dont think
all that is necessary.

 

[LS431o28]

I thought there is a way to tell how much refrigerant you have in the system by the pressure or by the load cant remember but i remember we used to determine this somehow.

 

[bippy93]

It's hard to tell by pressures, due to they change
with temperatures. Thats why your a/c does not
run when it gets very cold outside, because the low
side pressure gets to low to cycle the switch. Best
way is to reclaim and evacuate the system and start
from scratch.If you do still have a leak, I would check the
drivers side lower corner of the condenser. I'v had
2 explorers leak there.

 

[Garyboy]

This is a pretty basic observation I noticed when the wife's 94XLT didn't seem to be cooling as well as when it was new! It didn't seem to really move as much air thru the vests, thus over the evaporator coil as well. Before breaking out the gauges and getting serious I first attempted to check the evaporator visually. I removed air cleaner box, blower motor,etc. then with a mirror and flashlite looked at the evaporator itself. Just as I had hoped for it was lightly covered with the black fiber inside duct material. I blew with 160psi air pressure, then vaccummed, then used a fabricated fin comb to remove all fiber material. Put everything back together and it actually blew at least twice as much air thru the vents as before and the air was much, much colder. It actually allowed the evaporator to do its job with much less effort. Thus allowing the compressor to not have as big a load on it. So with 140K miles on it, living in Florida, its once again working at least as good as it did when new!! Vent temperature went from 55degres to 40degrees with just a simple(difficult really)evaporator cleaning. So therefore I consider this to be a really great thing to do as prevenative maintence on Explorer or any air conditioning systems. Also, I always attach window screen in front of the condensor/radiator to keep it clean and working at peak effiency. Gary

 

[Texan01]

Here's a very useful link for retrofits

http://www.delanet.com/~pparish/retrofit.htm

I'm going to agree that you'd best evacuate and recharge. start by putting one can in and see what you get, also you might want to clean both coils. I know my evap coil needs to be cleaned since I get leaves blowing into the cab.

An overcharge will cause insufficent cooling and high head pressures.