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When you assign an A/C job to a non specialist

If your shop’s A/C  specialist is busy and you want to get the diagnosis started, you can assign the preliminaries to any technician in the shop. Here is what GM asks a technician to be able to provide when he calls in with an A/C  performance problem:
•  A/C  high and low side pressures.
•  Inside temperature sensor reading.
•  Outside temperature sensor reading
•  Evaporator temperature sensor reading (if
•  Duct temperature sensor reading (if used).
•  A/C  refrigerant charge level.
This is actually  a  tough  one, because we ask, how canhe tell? We’ve said many times that the pressures  won’t  tell  you,  although  if  very  low, could be an indication. MACS recommendation (as it’s been for years) is to use an SAE J2788 recovery/recycle/recharge  machine  and  see how much refrigerant it pulls out.
Assuming you’ve  been  checking  the  scale  calibration, the machine should produce a number that’s accurate, and if the charge was correct, that number should be 95% or more of what’s supposed to be in the system.
If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit for more information.   Visit the MACS website at or email   
You can E-mail us at . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.
Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.

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