Originally Posted by Fred Jan (Post 4045319)

Will a parallel flow aluminum condenser will boost the AC ? I will take everything a part flush and put back with fresh oil

Originally Posted by Fred Jan (Post 4045320)

Thanks !! shall I pour the whole 7.75 Oz to the compressor itself, or pour some in dryer or condenser ... etc after flushing

Originally Posted by Fred Jan (Post 4045322)

Thanks for the notes !!! appreciate it, to narrow it down I bought a manual valve switch, I will plug it before the metal black hose in M103 engine gloing to mono valve (correct my information if am wrong) I replaced the monoo valve twice, once after market that was a piece of junk, them from apart car,I tested the coil its working and the seals are all good

Originally Posted by engatwork (Post 4045372)

Personally I'll add probably 75 to 80% of oil to compressor then remainder in other parts, dryer, hose to condenser, etc.

Originally Posted by Diseasel300 (Post 4045347)

Not as much as it will a Gen 1 W126 or a W123. The small-tube dual-circuit condenser of the Gen II W126 is quite efficient. It also has the huge benefit that it can be flushed, a parallel flow condenser cannot and must be replaced if clogged or compressor fails.
Use PAO68 oil. It is usable with R12 or R134a. All of it goes in the compressor, the Densos have a sump and do not require the oil distributed around the system.


Replacement monovalve core should ONLY come from the dealer. They're expensive ($130 or so) but the only ones that work and last. An old hardened core will not work, the MTC aftermarket ones typically don't work properly either. Make sure your coolant hoses are routed correctly.

You have not confirmed whether or not the coil is energized with the A/C running, you can only test it properly with everything hooked up due to how the transistor pack in the pushbutton unit does its switching. Adding a manual valve is totally unnecessary, the monovalve should stop all water flow to the heater core when the temperature wheel is set to the blue dot (max cold).

Originally Posted by upod (Post 4045645)

If there is a tear in the rubber diaphragm within the monovalve assembly, then you will get hot coolant circulating in the heater core when you want a/c.

Parallel flow condenser will work **substantiallly** better with r134a than the original tube condenser which was designed for r12. The original r12 condensers the w123 and w126 chassis Mercedes came with will work with r134a but will have lackluster performance in hot weather. You can get universal parallel flow condensers, but you will also need to know how to make custom a/c hoses, which a good a/c shop can do. Cabin temps will be in the 40's with a parallel flow condenser and r134a.

https://www.youtube.com/watch?v=M5lvHxCVxWg

Originally Posted by Diseasel300 (Post 4045707)

Sure seems like a lot of money to throw after a solution that isn't the problem. These Gen II W126's blow mid 40s on a 100+ day running 134a. I don't know what you think the parallel flow condenser is going to achieve since the pushbutton unit switches off the compressor when the evaporator coil reaches 38-41˚ (42-44˚ vent temp). The Gen 1 (Pre-'86) cars are a totally different story.

I'm just waiting for the OP to come back complaining that his $300 coil and $100+ worth of R12 didn't fix his problem.

Originally Posted by BWhitmore (Post 4045995)

When the system is operating do you see any bubbles in the sight glass located on the receiver/drier?

Originally Posted by Diseasel300 (Post 4045151)

You have other problems. The Gen II 126's are easily capable of delivering vent temps in the mid 40s in our heat with the stock system running R134a. You have a poor charge, a leaking monovalve, or a recirculation flap that isn't closing.

Originally Posted by Fred Jan (Post 4046026)

I see one solid yellowish fluid flowing by. Its not clear, I remember my old 1988 VW Passat LS that has the same as Mercedes Benz AC system, the sight was clear on R12, buy I heard you can't get the sight clear in A134A, is that correct ? that was back in the 1991till 2003 when I owned the car

Originally Posted by Diseasel300 (Post 4046041)

Absolutely incorrect. If the charge is right in the weather we're having (I'm in Texas too), you should have a clear sight glass. ZERO bubbles in our current weather. Cloudy/foamy/bubbling/opaque sight glass indicates low charge. Yellow suggests they have dye in the system, that should not be present if the system didn't have a leak previously.


You're obsessed with throwing a LARGE amount of money into converting back to R12 when the refrigerant being used isn't the problem.