I don't have an ETR switch .... but I think you do... If that is malfunctioning it could cause this symptom.

No I did not flush it this time because I had flushed it before to remove the 134? oil they had put in (that's if they did use 134 oil, they might've just put 134 in without flushing when they did the conversion that's why I converted back), I dont think we can trust any conversion to 134 these days since we just dont know what it was that they did. In any case I did'nt remove the oil this time because the ester oil used last time for the freze 12 ( I went from 134 to freze 12) is compatible with real 12 so I though that if I give it a good vacuum to remove the freze 12 traped in the oil it would be ok. I know I've had different refrigerants in there but I'll rather try my luck changing it back to original than to have an improperly done conversion just ruin the whole works.

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

Do you mean the evap temp switch? On the 124 they also have another temp switch for the heater core in front of the heater box and according to the cd's the ccu get imputs from this sensor to control the recirc flap. whooosshh...... another variable

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

My question was directed at the possibility that you have too much oil in the system.... that is one thing which will degrade the overall capacity of the AC...

It is an electrical switch which turns off the compressor when the evaporator gets too cold.

I put in 6 oz during the freze12 charge and then added 2 more during the real 12 charge to compensate for the oil lost when I took out the freze12. I must admit I wasn't 100% sure how much to put in originally but I remember seeing a post sugesting 6 oz for a full recharge.

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

I was also thinking of going back to my a/c books from school and refreshing my mind on how to measure superheat and maybe trying that also but measuring superheat is a PITA sometimes

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

You have all your switches maxed out , right ?

Since you messed with your vacuum deals.... I think you are going to need to eliminate the fresh air vent flap position sometime soon in this quest for colder air.

Superheat won't tell you anything on an expansion valve system. The whole point of the expansion valve is to regulate refrigerant flow the maintain a constant superheat.

You may just be dealing with an old, crudded up evaporator. After 20 years, there is likely plenty of dirt, dust, etc. imebedded in the fins of the evap. This stuff serves to effectively insulate the evap from the air passing over it, reducing heat transfer. I found that replacing the evap and condensor in my 87 wagon tremendously improved the performance of the a/c. Don't have any proof, but I think the nice, clean, straight, shiny fins on the new heat exchangers really help them work better.

When you're checking pressures be sure to have the blower speed on high and the windows down. You want to dump as much heat into the refrigerant as possible, otherwise your high side readings will be low.

- JimY

To clean the evaporator and condenser, what i did was go to Grainger and buy some Alki-foam condenser cleaner (non-acid base) $14 a gallon, the stuff the HVAC guys use. Mix in spray bottle 50/50 with tap water. Use gloves and eye protection.

Remove aux fans and shroud, spray on and let sit 5 minutes, spray off with hose, follow up with a blow gun, be careful as not to bend fins, straighten any that are bent.

Evaporator (w124), remove wiper arm, windsheild drains and blower motor, you will see evaporator (make sure you drain is not clogged) spray on and let sit like before, spray off, blow. alot say this is not good but all of mine drained out the bottom drain tube under the car.

evap and condenser is now bright sivler and clean! did the same for the radiator and oil cooler.

__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

I'm going to try and look at the flap today. I cleaned the evaporator the other day I used wheel cleaner and a lot of water and it really didn't have a lot of dirt on it.

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

Guys I found it . I blocked the coolant hose to the heater core at the fuse box with a flat pressure plyers and ran the car in city traffic and got 44 deg at the vent which is equal to 6.6 Celsius, the cd says 5 deg so am pretty close. I think the monovalve is letting a small amount of hot coolant to get by and of course you dont feel it at the exit point because by the time it gets to the monovalve the coolant is already cooled by the air coming from the evaporator, since the flow is not that much is not enough to totally kill the a/c, that's why I think I still get cooling as opposed to just hot air. Tomorrow i'm going to look for a valve or plug that I can put there while I figure what to do with the monovalve. I'll like to thank all of you for your help.

__________________
87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )