Original message
| beginner
 |  "car AC?"
, posted Sun 7 Aug 19:02  
This is the first time I am looking at a car AC. It is a 12 yrs. old car and never been to an accident. I know I need a 609 to work on automobile AC. I am just curious how compressor works in a car. The schematic shows 2 refrigerant pressure switches. There is a clutch. I am guessing the clutch is acting as a contactor. The only thing I can see is that the drier/accumulator is corroded badly from the bottom resulting from the salt during winter months. My gauge doesn't fit so no way to tell if it is low in R12. Anyone works on car before? I need AC in my car. LOL
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Replies:
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| Jet Mechanic
| "Re(1):car AC?" , posted Tue 16 Aug 19:21
OK, here is how it works: Basic air conditioning laws still take effect so I will not mention those. Depending on what type of vehicle you have, you have either a orfice tube or expansion valve. Most GM vehices will have a orfice tube. Your compressor turns on via switch mounted on the dash. Inside the evap box you will have a temp sensor that monitors the temp of the evap coil telling the compressor to cycle on and off. The lo and hi pressure switches are to prevent compressor malfunction due to either a lo refrigerant charge (leak) or a malfunctioning compressor which will cause a spike in pressure and de-energize the clutch. A thing to remember on most new vehicles, the ECM controls the climate control system in the following ways:
engine start up- this disables the clutch during engine startup via a relay.
Lo and Hi pressure switches- mentioned above.
Acceleration disable- when the throttle of the vehicle is placed in WOT (wide open throttle) the compressor clutch is disabled until WOT is no longer active.
Temperature control- the ECM monitors the temperature to cycle the clutch on and off to prevent a temp of 32 degrees.
NOTE: If you have a compressor malfunction on your vehicle and you change the compressor a code 66 will be stored in the memory of the ECM. Code 66 creates a ground in the engine start up relay and keeps the relay closed. This code can be created by a hi pressure sensor being activated. The only way to clear this code is by using a computer to erase the code or to disconnect the battery and wait 5 minutes.
This is the low down on how a auto a/c works. If you have R-12 it would make sense to go ahead and convert to R-134a while you have the system apart to change to receiver dryer/ accumulator. Contrary to belief, you do not have to change your compressor for R-134a. You need to remove the mineral oil from the system and compressor by flushing and adding PAG ester oil to your system. The drier or accumulator and TXV or orfice tube should be changed. Orings should be changed but do not have to be if you add oring conditioner to your system during charging. New R-134a orings are identified by their colors: Green and Blue with white dots or yellow dots (although some orings do not have the dots).
Good Luck
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| MasterTech
| "Re(1):car AC?" , posted Sun 7 Aug 19:25
I dont know much about cars. But if your 22 guages dont fit on low side then i doublt its R12 system. I have an adaptor for high side i think(been couple of years since ive worked on a car(.
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| | beginner
| "Re(2):car AC?" , posted Sun 7 Aug 19:38
I am very sure it is R12 for my vehicle. The manufacturer converted R12 to R134A from 1997 and newer models. When I have time, I will either purchase a new manifold for auto or just get the adapters. I was searching for the contactor in the beginning. LOL Then, I found some literature about car AC. It uses a clutch to start the compressor. This is totally different ball game to me.
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