Farm Equipment - 7020 Air conditioning

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7020 Air conditioning

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=21923
Printed Date: 12 Feb 2025 at 4:14pm
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Topic: 7020 Air conditioning

Posted By: farmboycitygirl
Subject: 7020 Air conditioning
Date Posted: 07 Dec 2010 at 9:46am

Hi all,

I have a problem with the AC on my 7020. I keep blowing the high pressure line from the compressor to the the dryer. The front of the tractor (condensor, radiator, etc) is clean and all the foam is in the right places. When I replaced the line the 1st time I replaced the evaporator valve as well, even vaccumed the system out to -30 and put the required amount of r134a. It worked well until the temps got into the 90's to 100's this past summer. I was baling hay and blew the line again. Got a new line put it on vacummed again, refilled, then compressor pulley bearings locked up broke the belt and now the high pressure line has a bubble in it again.

Not sure where to go from here, any ideas?

Replies:

Posted By: Hurst
Date Posted: 07 Dec 2010 at 11:06am

Have you replaced the receiver/drier? Checked to make sure that the evaporator doesn't have a clog. Also, is it a possibility that one of the other lines is collapsed/pinched? Definitely sounds like pressure build up somewhere. I would take things apart 1 by 1 and make sure you can get air flow through everything unrestricted. Have you flushed the system? There could be grime and junk that is clogging up the expansion valve. Also, make sure the hose isn't rubbing on anything, and if there's a chance it might, put something around it in that area.

Hurst

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1979 Allis Chalmers 7000
5800 Hours

Posted By: kev/ont
Date Posted: 07 Dec 2010 at 11:57am

sounds to me like there is too much refrigerent in the system. Have you checked with a guage to see what kind of high side pressures you are running, ( much more that 250 to 300 psi is trouble) There should be a switch in the system to shut the compressor down before you start blowing hoses. Somebody may have doctored with it over the years but it should be there.

Posted By: Joe(TX)
Date Posted: 07 Dec 2010 at 8:11pm

Do you mean the line from the condensor to the dryer. or from the compressor to the condensor?

It does sound like too much R134a in the system. There also should be a relief valve on the back of the compressor. Another possibility is that the hoses you are getting are not crimped properly.

Posted By: Brian Jasper co. Ia
Date Posted: 07 Dec 2010 at 9:37pm

A clog in the system causes low pressures, not high. When you say the "required amount" of R134, how did you arrive at that figure? 90% of the 12 to 134 conversions I have done over the years have worked best on about 1/2 to 2/3 the amount of 134 vs 12. Overly high high side pressures come from over charge, lack of air flow through the condenser, or a stuck open thermal expansion valve.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford