A/C issue

MOJOFAN

MEMBER
2003 CHEVROLET TRAILBLAZER
4.2L
6 CYL
2WD
AUTOMATIC
239,000 MILES

Single A/C. Old A/C was working fine, clutch got squeaky and noisy, but compressor made no noise of its own and was cooling. I replaced the compressor and clutch with a new unit. Added the proper amount of oil before installing. Replace the accumulator and orifice and low pressure switch. Old orifice was clean. Manifold gauges and vacuum pump, I evacuated the system and it held a vacuum. I began to charge 134a back into the system on the low side. I have gotten one and half 12 oz. Cans in. Full capacity should be about two and half cans. The compressor engages and runs about two to three seconds and shuts off continuing that cycle. When running, the pressures are about 20/175, when not running, static pressures are about 95/95. The compressor will stay running when jumped but haven't done that for longer than about thirty seconds.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Hi,

Thanks for the question. Looks like the system is still low. I think you know that based on what you said but when using these cans to charge the system yourself, they have a tendency to freeze and they no longer add Freon.

Your compressor short cycling like this is another indication that the system is still low. Plus depending on the outside temperature when doing this, the pressures show that the system is still low.

When these cans freeze, the internal pressure of the can drops and no longer pushes the Freon out. The compressor should be pulling it in but unfortunately when it short cycles like this it doesn't build enough suction to pull it out.

What I have found is you need to hook the can up and turn it upside down and shake it the entire time it is filling. This will prevent the can from freezing and you should be able to get enough Freon in it so that it stops short cycling. Once this happens, the compressor should do the rest however, keep it upside down and agitated until it is empty. So other tricks are to switch between cans as you are doing it so that you empty about half of one then the other and back and forth. This will allow the cans to warm up and you should be able to get them all in.

Worst case scenario, you will have to get a new can in order to add more. I would suggest getting the can that has a trigger and its own connection directly to the low side port. This will help force enough in to get the compressor to run properly.

https://youtu.be/XAlw_aoaPF8

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