Instructions on Charging over-road-ac unit

June 17, 2018, 02:06:12 pm

I have a 2000 Magna. Found the shrader valves loose and minimal pressure. Charged it up with a gauge set. Now reads 25 pounds on low and 175 on high with 80 degrees ambient. This is slightly low according to the R134 chart but I get plenty of cold air in the rear unit (55 degrees) but the front unit only gets about 5 to 10 degrees cooler than ambient.

If I start it up with the rear unit off, the gauge set only reads about 10 pounds low and 150 pounds high.

I do get a hissing sound from one of the bay units for a few seconds after I shut it down. I know that some automobile systems have a over pressure valve. I don't have any diagram. The only docs I found in the engine bay call for 5 pounds of 134a and 9.28 ounces of oil (PAG).

Not sure it ever worked properly since I bought it 10 years ago. That's life. Maybe a complete evacuation and recharge with oil is needed. Too bad I couldn't convince my former employer to buy the machine.

Any suggestions would be greatly appreciated.

Jon Baum
Magna 2K 5923

Re: Instructions on Charging over-road-ac unit

Reply #1 – June 17, 2018, 03:20:42 pm

Yahoo Message Number: 115281

Maybe the expansion valve or the receiver/dryer for the front a/c. On mine I can see them when I take off the interior facia panel. Pictures attached of the front OTR and rear units.

Bob K
1998 Affinity #5510

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