When the system is under a heavier load (ie really hot outside) it might not cycle.

 

Well this past weekend We drove 425 miles to NY and back. weather was warm, in the eighties. AC kept car cool enough for the four of us so no complaints there. Not sure if the clutch was cycling since on the highway with all the road noise you can't here it. Sitting at the rest stop though, I didn't here it cycling. I'm just worried that if it runs continuously do I run the risk of either burning out the clutch or destroying the compressor?

 

No sometimes it will run constantly. Mine stays on constantly most of the time too as far as I know.

 

Ok here's my update. Before embarking on another long trip I put some extra Freon in the system because the outlet temp was reading about 63F Well as I added a can of 134 the high pressure and low pressure readings didn't really change but the outlet temp started going up until it hit 76F so basically no ac. Didn't know what to do, panicked and bled off some charge. Next day got on the road and heard that familiar fog horn noise from expansion valve and no ac. Thought I smelled a burning smell so shut it down and went on vacation to the cape with no ac for the week. Came back and decided I fried the compressor so put in new compressor and drier, vacuumed it down and charged it up. I thought it felt plenty cold. Today my wife calls and says NO AC? I get home and checked it out and it's cool but not cold. Here's the thing. That stupid compressor still doesn't cycle on and off. just runs all the time. Had car for 14 years and always heard that compressor cycling so I know its supposed too. not even hot out, 78 degrees. put the gauges on and I am getting about 35 on low side and 150 on high side. That seems ok. Afraid to add more charge. I'm at a loss of what to check next. I checked the continuity on high pressure switch and it seems to be ok. I don't think its the clutch relay because when I started charging it, it was cycling on and off nicely. Once I had over 100psi on high side it just started running continuously.
Any ideas on what to check next????? I just about ready to send this beast to the bone yard and buy a Toyota!!

 

My a/c has never cycled. I'd suspect the expansion valve, but your pressures seem like they are normal though. I wonder if you have too much oil in the system if the cans you added had oil, stop leak, or other extra crap in there that decreases the efficiency of the system. Really you can't fill up the a/c based on pressures, you need to do it by weight. The amount you need should be on a sticker on the core support. Too much or too little refrigerant in the system can cause poor performance. It could also be possible that the heater core is warming up the air if the blend door isn't sealing it off properly anymore.

 

I put in 2 12 ounce cans. It calls for 1.75lbs which is 28 ounces so I'm 4 ounces short but I can't believe it would make that much of a difference. The expansion valve was replaced last year when I also had to put in new refrigerant lines and drier. I add only pure 134a, no added oil or stop leak. I thought about having too much oil. I drained the old compressor and yielded a bit more than 2 ounces so I added exactly 2 ounces to the new compressor. I also drained the drier which yielded 1/2 ounce which is what I added to the new drier. I thought that was ok. Tomorrow I will pinch off the heater hose to see if it is the blend door. The service manual says the high pressure cutoff switch opens at 450psi. That seems way to high considering at 80F the high pressure should read between 135-150psi. that would tell me you are correct and the compressor will never cycle. The service manual also says the compressor should cycle 2-3 times a minute so you can see the source of my confusion.

 

I'm also running 24 ounces. Honestly my ac is kind of random, some days it'll cool down into the 40s, others only to 50 or so. I'm guessing it's humidity. I just installed a vacuum heater bypass yesterday so I'm not sure if that's going too make a difference yet.

And there's also a temperature probe in the expansion valve that will disengage the compressor if it gets too cold.

 

My 02 dodge durango 4.7 2wd loses power and idles hard when ac is on,what could be wrong?

 

I think I'll add the another 4 ounces of charge to bring it up to the recommended 1.75lbs. Then I'll pinch off the heater hoses and see what that gets me.

i fell like I'm beating a dead horse here and I apologize for that but I thought I understood how these AC systems work but I'm feeling dumber the more I look into this. I did extensive rework on my Taurus AC also and that is running like a dream. When I put the gages on it the hi pressure rises until the copressor cycles off and then you can see it drop until the compressor kicks back on. Makes perfect sense. On the durango the pressure stays steady at around 135psi. It doesn't rise at all so of course the compressor won't cycle off. That just doesn't seem right.

As for the last post on the rough idle, sounds like the engine can't handle the extra load from the compreessor when it's on. That can be an indication of either a bad compressor or the need for a engine tuneup.

thanks

 

Is the ac working well, or is it acting up?


I'd be suspicious of the part of the system that regulates pressure between the two sides, the expansion valve. I've also wondered if adding some insulation to the suction lines in the engine bay would help any.