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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2007Compressor cycling fast
Hi all, I searched quite a few posts but could not find a match for all my symptoms. I have a 94 Chev silverado 350 and up until recently was led to believe my A/C compressor was dead. However, I got my hands on a guage and measure very low preasure (<10 psi) in the system. I added two 6oz cans of the R12a redtek and a leak repair can as well. This brought the preasure to approx 40-45psi. I now have cold air, but the compressor cycles much too fast in my opinion (approx every 3-4 seconds) when I the rpm's are up or when I am driving on the highway. Here is where it gets interesting: when idling, the compressor runs continuously, regardless of where I set the theromostat, and there is frost build up on the low side of the condensor lines. I checked for a loose switch wire on top of the compressor, but that is not the case. One more thing that I should add, but may or may not be related, is that this past winter I noticed that heat/cold thermostat was acting strange. It was hard to get the desired blend of warm/cold temperature (either all heat or barely warm). Any suggestions would be very much appreciated. Thanks. > Hi all, I searched quite a few posts but could not find a match for > all my symptoms. I have a 94 Chev silverado 350 and up until recently [quoted text clipped - 4 lines] > cold air, but the compressor cycles much too fast in my opinion > (approx every 3-4 seconds) ... You're probably low on refrigerant. Are you measuring the high side pressure also, or just the low side? Unless you know both you can't get a complete picture. You probably don't have enough of the right oil in it either but the leak 'repair' along with the 'R12a' will likely kill the compressor soon anyway... Thanks for your reply. I only have a guage to measure the low side. I mentioned above that the line below the condensor was frosting, but I meant the line below the evaporator. R12a not so good for compressor? In article <1181338090.625458.307060@h2g2000hsg.googlegroups.com>, > Thanks for your reply. I only have a guage to measure the low side. > I mentioned above that the line below the condensor was frosting, but > I meant the line below the evaporator. R12a not so good for > compressor? Do you know what R12a is? aarcuda69062 <nonelson@sbcglobal.net> wrote in news:nonelson- EAB5B0.20553708062007@newsclstr03.news.prodigy.net: > In article > <1181338090.625458.307060@h2g2000hsg.googlegroups.com>, [quoted text clipped - 5 lines] > > Do you know what R12a is? Potential "kaboom", from what I've read. The sh.t is marketed in Canada as "Duracool". It's legal, too. The "Toronto Star" newspaper in Canada has promoted it for Canadian automobiles. Says a lot for their credibility.  SignatureTegger >Thanks for your reply. I only have a guage to measure the low side. >I mentioned above that the line below the condensor was frosting, but >I meant the line below the evaporator. R12a not so good for >compressor? The manual for these may well not use pressures to diagnose the problems so don't worry about not having a high side gauge right now. It sounds like you are still low of freon. I'm not sure if the 94's used R12 or R134. The R12 systems had fittings that were relatively small whereas the R134 fittings are relatively large. Generally speaking, if the low pressure line is frosting up it's indicative of not enough freon. The "test" in the manual for whether you have enough simply is to feel the inlet (after the orifice tube, which means feeling the part very close to the plastic case the line goes into) and outlet pipes. If the inlet is colder then the outlet you don't have enough freon. Ideally they will be the same temp, more or less. If the outlet is colder then the inlet there is a problem somewhere. My experience has been that in hot weather it is VERY hard to overcharge a system. Not saying it can't be done, but you'll have to work at it. So if you don't have much trouble putting another half can or full can in, it's probably not going to wind up overcharged. That's where the high side gauge helps, you can tell if it's over charged by reading the high side pressure. Overcharging makes the pressure too high. > Thanks for your reply. I only have a guage to measure the low side. > I mentioned above that the line below the condensor was frosting, but > I meant the line below the evaporator. R12a not so good for > compressor? You are putting explosive gas into a leaky AC system? Talk about playing with a loaded gun.... Man I hope you or you passengers don't smoke... R12a has isobutane in it as far as I know. Just had a discussion on another group with some AC specialists about using that or propane in an auto AC system. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >Hi all, I searched quite a few posts but could not find a match for >all my symptoms. I have a 94 Chev silverado 350 and up until recently [quoted text clipped - 13 lines] >desired blend of warm/cold temperature (either all heat or barely >warm). Short cycling is usually due to low refrigerant or a blockage... orifice tube (or tx valve ) most likely. The static pressure (with the system not running) would give some indication of a very low charge. Be aware that R12A (hydrocarbon refrigerant) has around 30% of the charge weight compared to freon. If your system recommends a 40oz charge of R134A it will only require around 12oz of R12A. There's a complete manual at... http://www.hychill.com.au/pdf/hcm_e.pdf It's in metric units and won't have your model, but might otherwise be helpful. Hychill HR12 is the same thing as R12A. Dupont apologists tend to go ape at the mention of the stuff but it might be worth mentioning that in Australia anyone can buy it whereas it requires a license to buy (and use) freon. It's also now standard in a large number of new domestic refrigerators. It works better than R134A and is less prone leaking (since the molecules are larger). It's compatible with all refrigeration oils and won't damage your compressor. I've been using hydrocarbon refrigerants for years without a problem. So far not one of the countless number of systems running it has exploded, burst into flames or caused anyone in its vicinity to spontaneously combust (the DuPont team would have a field day if one ever did). :) SignatureJohn H > I've been using hydrocarbon refrigerants for years without a problem. > So far not one of the countless number of systems running it has > exploded, burst into flames or caused anyone in its vicinity to > spontaneously combust (the DuPont team would have a field day if one > ever did). :) That is not true. You're either ill informed or a liar. |
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