PeachParts Mercedes-Benz Forum - View Single Post

dmorrison · #36 06-15-2005, 03:25 PM

The PO may have installed the temp switch bolt because he may have hot wired the fan to come on all the time. Or at least when the AC is on. If so then do the following.
Check the system pressures to see is you are low on R134a. If so then fill it.
If not then get the fan on and run it all the time the AC system is on. This may be all you need.

Other posted info.

If you flush the ystem. You can use mineral spirits and then AC flush. Get a compressor and a flush gun or a Under coating gun, this is what I used, and completely flush the system. Get new O rings for the system. If buying new hoses then talk to Phil about the manifold hose. I tried 2 and returned them both. Phil was not happy with the hoses either. He may have found a better source. I reused my opriginal Mercedes hose. If you are going to buy a new manifold hose go OEM ($$$$).
New reciver/dryer. If you get a new compressor. Dont get a rebuilt. And make sure it is Mercedes compatable. Saw an artcle about the clutch assembly being rotated 180 degrees on the Mercedes units compared to the GM (for a GM car) units. The oil hole dumps the oil out if its a GM unit and you loose lubrication in the front seal.
New expansion valve if not R134a compatable.
Flushing the evaporator can be a pain if in the car. It will be, so plan on that PITA job.

GO WITH SYNTHETIC OIL. That way when your not happy with the R134a conversion, you can just evacuate the R134a and then install the R12. the synthetic oil is compatable to both R134a and R12.

ACKITS.com is your friend.

Again I would put some gauges on the system and see if you are low on freon. Get the fan working and see how the system does.

Get a good vacuum pump. If you don't pull a good enough vacuum and water is not completely boiled off then you may have the expansion valve freeze up with water as the system operates. A pain to diagnos and then you have to empty the system, replace the reciever/dyer, add oil, evacuate the system and then add your freon back ( if you had a collector) or buy new freon.

For R 134a they sell the top tap (Oreilly's sells them), but remember you should add the freon to the system thru the gauge hoses. Keep the can upright. Do not allow liquid feon to hit the compressor, vapor only. I run the can thru the hoses and advance the idle to about 2000 rpm. As the can get low put it in a pan of warm water. This will boil off the freon. Tthe water temp should allow your hand to sit in it. 100-110*F should be fine. Place a large fan, a box fan is good, in front of the condensor to cool the engine set up.

Dave