OT question about A/C

[71 LONG BED]

I have a general question on A/C. The A/C in my Jeep gets nice and cold for about 5-10 minutes then starts to blow warm. If I shut it off for a few minutes (sometimes longer then others) it will blow cold again. The condenser (behind the dash) was replaced 2 yrs ago ($700!). The compressor seems to be working OK (no strange sounds and it kicks on and off OK). Does anyone have any ideas what the heck is going on? My pregnant wife is driving it now and is a little cranky when she gets home from work on hot days.

Please forgive me if I have refered to the components by the wrong names.

[mrsnicks]

Sounds like you are low on refrigerant. Sounds like the compressor is cycling off when it runs low on refrigerant, and cycles back on when enough coolant has been recirculated for it to start again.


There should be a "check window" somewhere in the ac lines around the compressor. While it is running, see if there are bubbles in the window.

What year vehicle, what type of refrigerant?

Patrick

[71 LONG BED]

It is a 2001 Cherokee. The condenser was replaced because it leaked. I hope I don't have another leak! How much should it cost to recharge the system?

[71 LONG BED]

Thanks Pat. I'll give it a try. I hope I don't get shot in the eye trying to refill it.

[Thunderfoot]

71 long bed,
When you turn the engine off after it has stopped working like this, and get out of the rig, does it leave a big puddle of water under the rig after 10min or so? If so, it could be over cooling and icing up the evaporator (thing behind the dash) this should also cause the air flow out of the vents to decrees to though…
If it is low on refrigerant the compressor will cycle off an on fairly quickly (every couple of seconds) normal should be on for minutes or so and off for about the same depending on the outside temp… they usually wont blow real cold at the start either just kind of cool air.

[71 LONG BED]

I picked up a can of 134a, but we have been having some bad storms and a lot of rain, so I haven't gotten a chance to try refilling the system.

Thunderfoot, it does cycle on and off every couple of seconds, not minutes. Maybe it is almost empty. I thought that was what happened when it was empty but my buddy who did the work on the A/C said it was fine.
Do I have to worry about over filling? I don't have a gauge to check it.

[kid]

You are 1/2 full of Freon with that fast of a cycle. The sensor is in the high side of the compressor. If the compressor cannot boost the gas back to a liquid then there is not enough in the system to lubricate the compressor. That is why they break and the switch saves it. Our old trucks do not have a High side sensor so they die if they run low.

The inside part is an evaporator, outside coil is condenser and then you have a compressor. Smaller parts on your system is the pressure sensor, Dryer/Receiver and Thermal Expansion valve.

You don't want just a can of Freon you need a gauge with that bottle. I own a set of gauges, vacuum pump and adapter fittings. The can cannot over fill the system if you have a gauge. If the can was put on the low side it would over fill the system with no problem because the can would be at a higher pressure than the suction line(low side). The can fills the high pressure side so that when the pressure rises to the proper level the can and system balance out and stop the filling process.

[Thunderfoot]

Yep, like Kid said it is low with it cycling that fast... And you can overfill them so you do need a gauge setup to do it.

[kid]

That gauge and a 16 oz bottle cost me $26. Also there is leak detect that can inject into the connectors that can save your behind later. I use a spray on UV activated kind but the UV light I use from Fluke is another 29 so just use regular dye. High side will have a sensor mounted in it under the hood. Low side won't Hell I just raise the hood and go to work I don't think about it.

[71 LONG BED]

Thanks for all the help kid and Thunderfoot.
I'll stop and get a gauge tonight and let you know how I make out.

Hell I just raise the hood and go to work I don't think about it.

So do I, that's why I am wondering how to go ahead and do it right. I don't want to blow something up because I did it wrong.

[mrsnicks]

Thanks for all the help kid and Thunderfoot.
I'll stop and get a gauge tonight and let you know how I make out.

Oh sure, I see how it is, no thanks to me... I'm feeling the love.

[Wes]

no you can't fill from the high side w/ puncture can. If the a/c is running there is no way the can will have more pressure than the high side, also the possibility of the can rupturing.
Use the Low side (suction) to draw the freon from the can.

[kid]

My can fills the high side while running the R134 connectors have a one way valve in them. Read the can you buy with fill hose.

[71 LONG BED]

OK, I'll read the instructions tonight and go from there. If need be, I'll pick up an inexpensive gauge.

Thanks for all the help kid and Thunderfoot.
I'll stop and get a gauge tonight and let you know how I make out.

Oh sure, I see how it is, no thanks to me... I'm feeling the love.

I hate when that happens. Leaving someone out is the worst, sorry Pat.

Thanks for your help.

[Thunderfoot]

First, Yes Patrick you were correct in it being Low on refrigerant!

I had to do some looking as I hadn't seen the setup like Kid has with the single gauge…

So… Here is my 2 cents worth…

Here is a link to a DIY info http://autos.yahoo.com/maintain/repairq ... 023_0.html It also says not to hook to the high pressure side…

I have worked with HVAC guys that work on some of our equipment we have at work. It only has a port on the “High Sideâ€Â