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2005 MACS Clinic

TRB on Wed March 09, 2005 12:56 PM User is offlineView users profile


Attended the MACS auto a/c clinic last night and here are a few notes I wrote down. This clinic was pretty darn informative and I would suggest anyone with an extra $ 45.00 considering attending this clinic. has a list of locations and dates.

Enhanced R134a:

This was talked about at the past MACS convention in Las Vegas. Very little information was provided other then to say it could be coming down the road. What I was informed is this is not a new refrigerant but an upgrade in components to achieve better performance and lower leakage. Thus helping comply with the new EU standards that will be fully enforced in 2011 or 20012, forgot the date on that one.

CO2 Systems:
Point was made that one tool which is needed to check for CO2 leaks could run as much as $ 18,000 US dollars!

World shortage was the main issue as to why there was this huge price increase. My personal opinion is if that were the case, why have we not seen this same increase in commercial R134a refrigerant. Same stuff just packaged differently.

Refrigerant R152a:
It was stated that the refrigerant R152a is 100 times less flammable then current HC refrigerants.

BTU Issues:
Information provided stated that it takes 970 BTU’s to condenser 1 pint of water. One pound of R134a will create 70 BTU’s. So depending on the evaporator core size it could take many trips through the system before you remove the humidity and create proper cooling of the core.

VOV Valve:
I thought this was very interesting. It was stated that when using a VOV valve that a systems refrigerant level “must” be adjusted! How much depends on vehicle performance itself and not a set amount. So you could be adding or removing refrigerant for hours before you get proper cooling. Also if there is a small leak in the system this would then effect the charge level creating a improper charge level for the VOV valve, thus poor cooling. It was stated that all OEM attempts to use a VOV valve were stopped. I think someone somewhere in design may still be working with them but it sounds like this is not really an option we will see in future vehicles.

Refrigerant Loss:
It was suggested that in an orifice tube system the loss of as little as 1 ounce of refrigerant a year could create a compressor failure. Vehicles with service caps missing were have said to produce a 1-ounce per year leakage rate. It was suggest that anytime you work on a system that new service caps and Schrader valves be replaced. I would also suggest coating them with Nylog during assembly.

Accumulator Concerns:

Every accumulator has a small oil pick-up tube inside the canister. It was stated that research has shown even a very small amount of debris in the system could plug this oil pick-up tube starving the compressor of oil creating a failure.

Refrigerant Charge Level:

Correct refrigerant capacity should always be followed!

Temperature between the inlet and outlet of the evaporator should be close to 2 degrees when a system is correctly charged.

Condenser Inlet/Outlet Temps:
When an auto a/c system is operating correctly with a proper charge you should see a difference of around 25 degrees between the inlet and outlet of the condenser.

Electric Fan Addition:
Checking the amp draw in an open-air position before installing should be preformed. Then manually place the additional cooling fan in the position you plan to install it. If there is a decrease of 5 to 10 amps you have created a cavitations issue blocking air flow through the condenser. If this occurs you actually are better off not to add the additional fan. Try moving the fan to different parts of the condenser, if you find a cavitations issue.

OEM Tech Links:
For attending this clinic we received a goody package. This package has a dozen or so links to OEM tech sites. Some were suggested as free sites and some were not. They were short on the goody bags so I gave mine to others. They said they would get a goody bag over to me later this week so I’ll posts these tech links when available to me.


When considering your next auto A/C purchase, please consider the site that supports you:

Edited: Thu March 10, 2005 at 4:54 PM by TRB

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