Alright, well I finally decided to use my A/C for the first time this year today, and guess what... you guessed it, it wouldn't work. The A/C clutch will not engage and the system is blowing very hot air out at max (blue) A/C and the fan speed on max. Well I bought a 3oz bottle of Quest Super Seal and an 18oz bottle of Quest Sub-Zero Synthetic R134a, each about $30. I checked the system pressure when running and got a reading of 0psi (the clutch will not engage at this point). So I put all of the Super Seal in the system, but nothing happens. Then I immediately start filling with the Sub-Zero, and start getting a pressure reading that finally gets up to about the 50psi mark and the compressor starts spinning but only for a few seconds, then it starts cycling on and off about every 10 seconds. Meanwhile the gauge reads at 50psi with the clutch off and when it engages it reads about 12 psi then goes back to 50psi when it shuts off. Any idea what the problem could be??? Bad sensors/switches, bad compressor, bad accumulator, etc.... Thanks in advance

Is it safe to jump the compressor to the battery to get the clutch to stay on?

 

that's what i do. others will say different, but ive done this on many vehicles i have owned with no problems down the road. also remember to shake the can to force all the refrigerant out into the system.

I like the plate on the front of your blazer in your sig. Go Cards.

 

Well, I guess I'm gonna try to jump the compressor to the battery if no one has anything negative to say about it.

 

Sorry I wouldn't suggest doing that. The compressor is shutting off on pressure you could have a serious blow out if you jump the compressor to the battery.

I work on A/C for a living and just had the same problem with my brothers truck. There is a blockage in the line somewhere in his Dodge Ram it's something called an orifice tube. I haven't had to work on my Blazer's A/C yet to know what could be causing the blockage could be the accumulator or the likely culprit is the expansion valve. The orifice tube is a replacement or substitute for and expansion valve on Dodges. Where ever there is a screen on the system has taken on some dirt and is blocking the one line on the A/C causing the compressor to raise the pressure very quickly and then shut off. I'll do some research on the A/C system on the Blazer and see what I can find.

Just checked things out on the internet and there appears to be an orifice tube on the Blazer too. I will bet that the one on your truck is clogged the part consists of a screen and a small tube the screen gets clogged with little particles of stuff from the inside of the A/C lines and blocks the flow of refrigerant. The orifice tube should be on the line coming off the condensing coil going to the evaporator.

 

But the pressure is decreasing when the compressor clutch engages, not increasing. When the clutch is not engaged the pressure was 50psi, when the clutch engaged it dropped to about 12psi then back to 50psi a few seconds after it stopped spinning. And I haven't added nearly enough refrigerant to refill the system from a 0psi reading.

 

Which is exactly what the pressure should do if there is a blockage in the line the compressor sucks all the refrigerant you are putting in away and leaves you with 0 pressure. My brother's truck did the exact same thing and just from my experience working on residential A/C I knew what the symptoms meant.


Here is where it is located shouldn't be too hard to get to. http://autorepair.about.com/library/faqs/bl841h.htm

 

The system is working exactly the way it should! Dont bypass anything! My 98 takes 1 pouns 12 oz of refrigerant. You only put 18 oz in. the system is low. That is why the compressor is cycling on and off on low pressure. Please google how auto AC work and educate yourself on how an orifice tube ac system works. They are very simple. But it is critical to have the proper amount of refrigerant in the system. It is never a good idea to modify a properly operating system when you dont know the how or why it is doing what it is.

NOTE - If the orifice was plugged, the pressure wouldnt rise after the compressure turns off. Also - You dont have to shake a can of refrigerant to get it all in. It is boiling inside of the can as the vapors are being pulled into the system. Its like saying that you need to shake a pot of boiling water in order to get it all to boil away.

Please learn how the system works. it will be less expensive for you and SAFER!

Good luck!

 

Yep, I did a lot more research before I did anything and came to the conclusion to let the pressure reach the critical (red) area of the gauge and it paid off. Just about all of my old refrigerant escaped, so my system needed a lot of refrigerant. In order to get the refrigerant level back to operating level you have to go beyond the safe psi level to fill the system. It eventually came down from about 65psi when it was cycling on and off to a steady about 30psi, then slowly climbed as I kept adding. When it came back down to a constant roughly 30psi the clutch stayed engaged the remainder of the time. The leak is somewhere LOL, but the stop leak dye hasn't shown where it is yet. Hopefully the stuff solved my problem. So far I've added a total 32oz of R134a and my gauge tells me I still need more. The A/C is blowing cold now but not as cold as it was before this happened, which tells me my gauge is working correctly. Thanks for all of your replies and I will post back up if my problem persists after I add some more refrigerant.

 

if you are trying to use the Pressure temperature (Super heat method) of topping off the system im afraid it just isnt going to work the right way. You mention the guage in the red when the compressor is off. That is correct! The pressure you are concerned about is the Low side pressure while the compressor is running. (Which DROPS while the compressor is running.) If you hook to the high side the pressure goes up while the compressor is running.

Part of the reason you should weigh the charge in is due to the fact that the compressor is variable speed. (Actually designed to run at 1200-1500 RPM. If you are charging at any other speed the low side pressure will be inaccurate. Another reason in the ac generally is on as the car is going down the road. which means ALOT more air is passing through the condensor. This results in a lower head (Or Highside) pressure. Lower head pressure results in lower low side pressure. Just too many variables to trim the charge properly.

If you have added 32 oz to your system, it is over charged. It is only designed for 28. An over charged orific tube system will not cool properly. You also run the risk of liquid refrigerant coming back to the compressor, dilluting the oil, scoring cylinder walls and slugging the compressor. Slugging the compressor results in broken valves. Over charging forces more refrigerant into the condensor which causes an artificially high head pressure. This causes undue stress on the compressor, and forces more refrigerant past the orifice into the evaporator. High evap pressure prevents adequate cooling.

 

There is a label on the heater box that gives total system capacity. Mine says 1 pound and 12 oz. That is what the system is designed for. If you add too much refrigerant, the high side pressure will climb to the point that the high pressure switch will shut the compressor down. This will fool you into believing that the system is still low. If you run the compressor stright to the battery like some people suggest. This safety feature is defeated. I believe there is a safety valve that will vent if the pressure gets too high. If there isnt, then some part of the system will just burst from the 450 psi