Monovalve? 1987 420 SEL

Hello all, I am new to the forum and have previously posted and got wonderful responses from all of you, Thank You. My MB obsession started back in the 90's when my friend talked me into buying a 1981 240D. The car ran like a top with minimal expense and finally bit the dust,I believe it was the injector pump. Anyway my new (old) ride I am obsessing about is a 1987 420 SEL. Great shape, 129,000 miles and runs like a top. I had an MB indy repair the rear axel ,new tranny filter and fluid and repair center pod and check the timing chain and guides. They came to the conclusion that my timing chain and guides were good,we'll check it on your next oil change. My question to you'all, the AC is fully charged and not leaking(according to a different shop).I can see a couple bubbles in the sight glass when I turn on the AC and then they go away,but the AC doesn't blow real cold,it seems as thought their is some humidity in the system and I am figuring monovalve. I have one on order and am going to replace it regardless. Is this feasible? Any ideas or speculation would be greatly appreciated. You guys know what you are talking about!! Thanks.

[E150GT]

I do not believe the monovalve has anything to do with A/C other than it can overpower it with heat.

It seems to me their is a battle between the AC and the heat. The AC is humid. I am also going to make sure the fresh air intake is closing.We have had a tropical storm so I am afraid to get the car opened up,at that time a squall will soak everything. Does that sound feasible? It has already been converted to 134a from a previous owner.

[E150GT]

How cold is not real cold? What temps are outside? I know that if the monovalve it leaking, then the car would pretty much have full heat and no A/C.

I have not put a thermometer on it,it just isn't as cold as AC should be,and it is humid.When I turn it on it blows out of defrost for a couple seconds and fogs up the windshield,very humid.

[ctaylor738]

Even if the R134 conversion was done correctly (sensors, schraeder valve, etc.), it may not cool a big car like yours in your climate. A friend of mine with a 560SEL is adding a second condensor to get his system to work better.

With that said, does the air blow colder right after the engine is started? That would indicate that hot water is getting into the heater core, or that the flaps are not moving into the "cool" position.

It never really gets that "cool" unless long term highway driving , i am stumped

[ctaylor738]

Well, if your pressures are good, then the system is only working well at higher engine speeds, which takes you back to the fact that R134 does not cool as well as R12.

Are the auxiliary fans coming on? That can make a difference in traffic.

[JimFreeh]

Originally Posted by Gummy67

I have not put a thermometer on it,it just isn't as cold as AC should be,and it is humid.When I turn it on it blows out of defrost for a couple seconds and fogs up the windshield,very humid.

Well, that's another couple of unrelated issues.

You've either got a low amount of vacuum, due to leaking pods, or bad lines.

Fogging is a result of either a leaking heater core, or a plugged condensate drain.

Jim

Plugged condensate line,I will have to check that for sure.I did notice it doesn't create near the condensate my truck does. Could condensate not draing cause my AC to be humid?

I am going to clean the condensor,how do I remove the auxilary fan??