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TOPPING OFF DUAL SYSTEM A/C
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NKENN
New User
May 4, 2012, 11:17 AM
Post #1 of 4
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TOPPING OFF DUAL SYSTEM A/C
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2001 FORD EXCURSION LIMITED 5.4L 205,299 MI Is there any "rule of thumb" for topping off a dual a/c system. This system uses a TXV in the rear and an orifice tube in the front. Can I use clutch cycling time correlated with ambient temperature to get a good "guesstimate" of charge? Any suggestions would be greatly appreciated. Cannot give specific temperatures/pressures as I haven't checked them yet. I just know the system performance is not up to par at this time. I have topped it off a couple of times over the last 4 years with satisfactory results. I just wondered if there is a more precise method to do the job. THANKS
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Hammer Time
Ultimate Carjunky
/ Moderator
May 4, 2012, 11:19 AM
Post #2 of 4
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Re: TOPPING OFF DUAL SYSTEM A/C
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There is no rule of thumb or correct way to top off any system You cannot know how much refrigerant is in the system without completely recovering it and weighing the new charge. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 4, 2012, 11:32 AM
Post #3 of 4
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Re: TOPPING OFF DUAL SYSTEM A/C
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Exactly as said. With dual system, one CCOT the rear TXV the rear can hog the condensed refrigerant and #s are nuts so no "rule of thumb" really applies. Don't know what you used to top off before but if that junk had sealer or stuff in it you could be in trouble now. As HT said, best way is to recover what's in there and charge to exact known weight listed underhood somewhere and if it isn't near perfect then there are problems to deal with. Don't just go boosting systems till you really know what you are doing. You risk ruining the system or worse, hurting yourself, T
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nickwarner
Veteran
/ Moderator
May 4, 2012, 1:38 PM
Post #4 of 4
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Re: TOPPING OFF DUAL SYSTEM A/C
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With HT and Tom here. Your compressor needs to draw in vapors, not liquid. By its very name it compresses and liquid is incompressible so very expensive BANG noise happens. If you can't tell how much is in the system you won't know if you overfill it. If you just go by how cold it can blow through the vents you may have a marginally adequate charge but will have much more frequent and longer cycle times, which will greatly shorten the life of the compressor. The proper and actually cheapest fix in the long term is to find out where you are losing the refrigerant, repair the leak and charge the system back to spec with the exact weight or refrigerant. Its a gamble doing it any other way.
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