Outside temp is more like 90 so the pressure should be a little higher I think.

I have the Mopar Factory service manual that says at 90F ambient, the pressure should be 50-60PSI (or maybe its 40-50 PSI ... its sitting in my truck).

The thing I am trying to figure out is does it take so long to fill up or is my gauge bad. I've read that a 14 OZ can of r134a could take 15 minutes to fill up but how much would this increase my pressure?

I am a little confused, maybe i got a bad gauge. Maybe there is another problem. I was sitting there for like 15 minutes and it was barely going up, then all of a sudden I got the pressure and it was at like 120 PSI--did my compressor shut off or something?

I think when the compressor shuts off, the pressure at the low port will go WAY up ?

My problem is the air blows cold then all of a sudden turns HOT. Maybe I need to take my pressure test when it turns hot.... I'm pretty sure the compressor is still going when the air turns hot, is there a way to tell? Usually I'll turn the a/c control off then on and listen for the click and hear the increase load on the engine.

 

I am sure that it is freezing. When it blows hot, switch to the heater for a little while and then back to AC. When you first go to heater, you won't feel much from the vents.

 

shouldn't a properly functioning system not freeze though? I've never had this problem before... seems like a work around not a solution... (?)

 

I am having ac problems as well on my '01.

I bought gauges tonight, hooked them up and compressor was cycling fast, about 10 seconds on and 10 seconds off. Low side pressure would build to 55 psi and then drop. High side pressure was about 25 psi.

It was about 90 degrees outside and the chart in the FSM states that it should be running about 60 psi low side and 250 psi high side. The high side never went higher than 50 psi.

Now, it started to blow cold sitting in the parking lot of the parts house but once I started driving it started blowing luke cool.

I am ready to fork over the estimated 800.00-1,000.00 to lay the liability on somebody else.

I swear, I picked up a 76 Wagonner that had been sitting for years in a cotton field, put a motor in it, added two cans of R12 and the son of a gun would freeze my nads off (38 degree's) and did so for 2 years. On top of that, it drove a helluva lot better than my Lukes Linked, new tired, recently aligned Dodge. Hard to believe they were built by cousins in the industry.

Oh, the other problem with the a/c is the cold air blows out the floor vents and I cannot determine why; actually, I've given up.

 

Ok guys, my evaporator is freezing up too.......it blows very cold for 10 minutes then freezes......the compressor doesn't cycle......it just stays locked on and won't shut off unless the AC is turned off......does this mean I have a faulty pressure switch that is not turning the compressor off? Would this be a bad high pressure switch or a low pressure switch? Are these pressure switches something I can change myself? I have very little AC experience and would appreciate any guidance from you guys.

 

Odd, no one has mentioned moisture. If there is moisture in thesystem it will collect at the capilary tube and freeze it shut or nearly shut. Turning off the system for a minute will thaw it out. Turning it back on will give you full cold. I have a problem with this at idle speeds. As soon as I hit a light on the highway the cooling will go away until it thaws and starts working again. At highway speeds it will keep working endlessly.

My system was open for some time and I have flushed it and replaced the filter/dryer, but still has some moisute. In the near future I will flush it again and replace the $90 dryer again...

 

Did you pull a vacuum?

A good friend of mine recommended drawing it down for 6 hours.

 

I still think my particular problem is with a pressure switch because the compressor never shuts off as long as the AC is on.......it just blows cold for 10 minutes, then freezes up and the compressor just stays running.

 

If you are sure it is the switch, change it.

 

Mine was pumped down the last time for 8 or 9 hours. Went to bed, charged it the next morning. Used a big commercial vacuum pump I borrowed.

 

That sure should have done it

That sucks that you have to do it again.

 

If I was sure I think I would change it.....can I change a pressure switch safely and without losing any freon?

 

Yes you can change the low pressure switch without the freon leakign out. Just fixed my a/c today. It ran 309K before I even had to add any freon. The compressor clutch broke this week, and I decided to replace the compressor and accumulator. I wanted to replace the orifice/filter but on a 98.5 it's in the middle of the liquid line and the whole line must be replaced. More dumb engineering. Anyway it worked real well, 40 degrees with 90 outside. Have 2 98.5's and they both went out the same week. Bought a new compressor and accumulator for the other one today. I think that the compressor is the first part that's installed on the truck on the assembly line. It's not near as easy to replace as the factory service manual reads.

 

I would tend to agree with Haulin in Dixie, on his diagnosis of moisture inside the system. That is a cause for the stated problem. BIG MIKE

 

OK my A/C is now no longer functioning at all and it's 112 F outside. I get pure hot air.

The compressor is cycling on and off like crazy.

When I hook up the gauge to it it's at like 20 PSI then it shoots up to like 60 PSI as the compressor cycles. I'm guessing that the pressure shoots up when the compressor turns off?

So am I safe to try to add more refrigerant to the system here and when it gets enough, the compressor should stop cycling quickly????

I can handle the heat but getting soaking wet then going into a 60 F office building sucks.