From: Wally Plumley [wplumley@avana.net] Sent: Wednesday, June 07, 2000 3:50 PM To: 928 Subject: [928] Re: A/C question At 10:03 PM 6/6/00 -0700, ADAM BIRNBAUM wrote: >Questions: >1) Is my compressor acting typically, or should it run any time I push the >A/C button? The compressor clutch should engage as soon as you push the button. It should then run as long as the A/C is on, EXCEPT that there is a "freeze switch" that monitors the temp of the evaporator and turns the compressor off when the evaporator temp goes below freezing. This keeps the evaporator from icing up. There is also a pressure switch on the receiver/dryer that will not let the clutch engage if there is no freon pressure in the system. (The compressor depends upon the oil that circulates with the freon for lubrication, so no freon means no lube, which ruins the compressor.) If the compressor clutch doesn't engage, check the freon pressure. If that is OK, the problem is often the A/C relay in the HVAC control head. There is an excellent repair procedure (written by dr. bob) in the archives and on Greg's Tips page. >2) Since I saw air bubbles in the sight glass, I'm assuming that I have no >(major) leaks in my system, correct? Nope. There should be a stream of bubbles for about ten seconds when the clutch first engages. The sight glass should then clear and stay clear. The receiver/dryer is a can with mixed gas and liquid freon dribbling in from the top. The outlet tube almost touches the bottom, so it should be pulling pure liquid for the expansion valve. If you get bubbles while the system is running, you are low on freon. >3) Is there any way for a tech to tell if I have R-12 or R-134? It is required that the service valves be changed from the standard 1/4" flare to an acme thread when the system is converted. If you still have the standard fittings, you should not have R-134a. EPA is rigid in the enforcement of this. It is actually pretty difficult to do an "outlaw" conversion without changing the fittings, because everything having to do with R-134a uses the acme threads. If you have an outlaw conversion, it can lead to serious cross-contamination of a shop's reclamation system and their supply of reclaimed R-12 - not good! >4) If I still have R-12, where can I top off, or do I have to convert? You can still legally buy R-12 across the counter at most parts stores. You have to become certified to do so, however. This is pretty quick and easy. The only reason for certification is to ensure that you know that freon should not be vented, but should be recycled, so the test is very, very easy. You can get certified on the web. >5) Is my shark now considered a hybrid because I've got a blue oval >compressor? Ford conversions are pretty rare. Charlie Griffith offers an aftermarket compressor conversion kit for 928s. Wally Plumley 92 Specialists From: Wally Plumley [wplumley@bellsouth.net] Sent: Tuesday, March 20, 2001 2:35 PM To: 928 Subject: [928] Re: AC compressor INOP At 01:49 PM 3/20/01, you wrote: >1) Are there two service points on the 87s4 AC system ??..#1 port up front >near the sight guage which the tech said was the HIGH PRESSURE SIDE and #2 >port on top of the compresser itself the LOW PRESSURE SIDE(we found after >a phone call), the place where the freon is introduced????????????????? Yes. The high side is at the receiver/dryer. The low side, where the freon is put in, is hidden on the large A/C line between the radiator and the engine just under the coil on the passenger's fender. >2) which one do you pump/service the freon into?? Low side under the coil. >He had tried port #1 to no avail because he said this must be the HP >side..there must be a LP port somewhere?? Uh-oh. This instantly tell me that he isn't an A/C expert. Anyone who knows anything about A/C would know that the receiver/dryer, and that port, are on the high side. >At this point we didnt know #2 was on top of the compressor. I hit the >Speeddial on the cell to 928intl and found out there is a port on top of >the compressor as well...the tech said this MUST be the LOW PRESSURE SIDE >and this is where you service it. he unhooked the hoses and tried it there. He should have had one hose to the high side, one to the low side. If you don't have the high side hose connected, you don't really know what the system is doing. You need both hoses hooked up. >With the engine on and AC engaged again he started the process. The >problem lies in that the freon level/ his guage wasnt dropping in his >tank? We checked all his connections by slowly lossening them to see a bit >of freon spray out....did this all the way to the port on the compressor. >HE SAYS THE COMPRESSOR IS SHOT BECAUSE IT ISNT SUCKING/DRAWING IN THE >FREON FROM THE TANK? Does this make sense? Nope. Sounds like the port on the compressor is a service port with a valve that must be opened, ot his hose fitting didn't have the little tab to depress the schrader valve in the compressor port, or ?? >Now to me, using my knoweledg on weather...things flow from HIGH TO LOW >pressure. Even if the compressor was OFF..shouldnt the HIGH PRESSURE >FREON in the tank flow into the LOW PRESSURE port on the compressor even >if it WASNT running? Yep. In fact, if you start with an empty system, you can let liquid freon flow into the system from the tank. Remember that the high side/low side pressures will be the same unless the compressor is operating. You normally charge the system with the compressor running. This is a good time to point out again that if you compressor operates, the system ISN'T empty. The compressor won't run if the system is empty unless you disconnect and jumper the freon pressure switch harness. >Does it really SUCK the freon out of the tank or around the system in the >car? To me the pressre in the tank should have dropped the minute he >opened the valve regardless of AC operation?? It might not have dropped much if any. One of the characteristics of freon is that if you have both liquid and vapor in a closed system, if you know the temperature, you know the pressure. In other words, if the compressor isn't running, and you have an ambient temp of 70 deg F, you will have 70.2 psig in both your car and his tank. If the car is warm from running recently, the pressure in the car is going to be higher. >ANYWAY...with the AC engaged.......there are a few bubbles present in the >sight guage...the clutch engages....there is a faint hisssing from the >evaporator housing behind the center vent. These ALL tell me (the clueless >one on AC) that the compressor is perhaps indeed working and that the TECH >is #%#%ing up. Right. >I dont want to fork out $$$ for a compressor right now...at least it is >still window weather in Vegas. You don't need a compressor. You need to learn how to work on your A/C. >3) is there a "safety" that has to be released on any of these ports to be >able to allow freon to enter or escape? (besides the schrader valve) >Sometimes, but not usually on car A/C units. The house system has service >valves that have to be opened. > >Any tips..pointers..BTDT regarding AC service and what to look for would >be awesome. >Besides, with summer approaching us all.it could be useful to all of us Buy a book. Read it. Wally Plumley 928 Specialists