2002 Mazda b2300 Air Conditioning Cycling

2002 MAZDA B2300
53,000 MILES • 2.3L • 4 CYL • 2WD • AUTOMATIC
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BUILDING2
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The unit was cycling rapidly on and off so I evacuated the system, pulled a vacuum (no leaks), and weighed in the correct charge 1lb14oz. When the vehicle is idling in park or neutral, the system works perfecting with no cycling. Pressures look great. As soon as I place it in drive, the a/c starts cycling on and off and the idle "hunts" between 600 and 1000 rpm. As soon as I place it in neutral, the unit operates normally. I do not have any OBD II codes shown. The unit seems to cut out at about 30 psi and high side around 225 psi well within normal operating ranges. I bypassed both the HP and LP pressure switches and it continues to operate as described above. I would appreciate any information you can provide. Thank you.
Aug 19, 2014 at 9:40 AM
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HMAC300
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heck the air gap on magnetic clutch at 3 separate spots range is in picture.our manual say 1.85 lbs is what it should hold and if you did it by cans instead of a measuring device most of those only hold 12-14 ozs. so recheck your amount as well. the 30 psi may be a little low as well
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Aug 19, 2014 at 12:34 PM
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BUILDING2
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Thanks for your response. The charged was weighed in from a 30# can. the charge shown on the vehicle data plate is 1lb. 14 oz. which is 1.875 lbs. The clutch gap is within tolerance. The 30 PSI reading I gave was approximate - it may have been 35 PSI, I don't remember what is was exactly. Any other suggestions? What head pressure should I have with a 95 deg. ambient and at what engine RPM ?
Aug 19, 2014 at 1:04 PM
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HMAC300
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with 98 degree ambient it can be 50-55 psi on low and 275-300 on high. but that is according to a pressure chart it should be higher than 30 psi on low side however. it almost seems like it's flooding the system to me was anything replaced on this other than Freon? Or is this a truck you picked up as it may have the wrong components in it. if it's the srong component like a condenser you may need more 134 in it.
Aug 19, 2014 at 1:58 PM
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HMAC300
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only other thing that I can think of is the wrong orfice tube is in it causing the flooding of system.
Aug 19, 2014 at 2:02 PM
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HMAC300
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you know looking into this further I think you have a bad high pressure switch as you say it cuts out at 225. look at pic for description. it should cutout at over 400 psi
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Aug 19, 2014 at 2:08 PM
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BUILDING2
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I bought this truck brand new in 02. Nothing has been replaced on this a/c unit. Just recharged. Keep in mind it works perfectly with discharge temps in the 40 to 50 deg range. This drop in engine rpm and the hunting along with the clutch disconnecting does not start until it is placed in drive. When driving (increased rpm) the system works perfectly.
Aug 19, 2014 at 2:09 PM
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BUILDING2
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As I noted in the original question, I bypassed the HP switch and it continued to cycle. I also bypassed the LP switch, same thing.
Aug 19, 2014 at 2:18 PM
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HMAC300
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for the a/c I haveno idea what to tell you then. for the hunting try cleaning throttle plate on both sides an iac hole with choke cleaner. it may be a trans problem if you are feeling slipping though like a converter or od clutch as far as the a/c system one other thing is try to clean ground for a/c clutch its 'at lh front of engine compartment unless the a/c clutch relay is going out on it I really can't think of any other reason for this........ if you'd like you donation back recontact me and i'll see that it's done. try switch ing a/c relay with a like relay see if it makes a difference.
Aug 19, 2014 at 3:50 PM
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BUILDING2
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Thanks for your help. No need to refund the donation. I'll try switching the relays. I thought it may be the WOT relay but after thinking about it I don't see how it could be. Thanks.
Aug 19, 2014 at 3:59 PM