87 300d turbo, new vacuum pods, new filter dryer, 35 oz of r12, pulled a 1.5 hour vacuum, vented hoses before charging, got aux fan direct on high, no leaks, inside temp sensor holds a piece of paper, hose after monovalve feels just a tad warmer than ambient temp, I think is because of eng compartment temp, suction hose sweats up a storm all the way down to the compressor-even the rubber part sweats-, metal part of hose feels very cold, pressures are 29 low side, 148 high side, 73 deg ambient, 87% humidity, I get 50 deg at the vents and 49 deg if I drive around in city driving 2 lights at a time, did not go on the highway. I just dont feel it cooling that well , tonight it was fine but tomorrow in the sun it will be worthless, any sugestions?

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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 FSM AC book only goes to 1985...
1. Where did you get the 35oz figure for the refrigerant ?
2. Were you using the small cans or a big canister ?
3. Did you use warm water on the cans ?
4. What kind of vacuum pump did you use ?
5. Do you know what inches or mercury or microns you pulled ?
6. How did you decide that 1.5 hours was enough time vacuuming ?
7. Did you flush the system ?
8. If you did not flush the system how did you determine how much oil to install ?
9. If you did flush how did you measure the oil you placed in the system ?
10. Did you install a new TxValve ?
11. What happened to cause you to redo the system ?

system takes 2.2 pounds which works out to 35.2 oz, I put in 3 12 oz cans which is 36 oz but you can never get it all in there so I fig I put in 35 oz since not a lot was left in the cans when I disconnected them, I used hot water to aid in charging. I have a 4 cfm vac pump which I must say is a little weak now since it only pulls 27-28 in hg now, I switch back to 12 after trying out freze 12, the system had been converted to 134 with inadecuate cooling so I flushed it and charged it with freze 12 and 6 oz of ester oil, this time I added 2oz to compensate for lost oil during the recharge. How low should the temp get at the vents, I was looking at the cd's and they have a table with diff temps depending on outside temp.

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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 )

Ask Larry Bible... he is an AC pro and has that very same car...

Is fan Hi speed really high speed?
Does airflow feel strong?
Does Recirc help?

Is the sight glass clear and what are your pressures at what temps?

It's great that you replaced the vac pods, but is the recirc door closing? I don't know any way to check it without some disassembly, either pulling the blower motor or dash. It could be that by pulling the glovebox, you can see the edge of the fresh air door. Jim Yuhn would know the answer to that.

At this point, it might be worth disconnecting the hose to the heater control valve (this car does not have a monovalve) and block it off temporarily and see if the vent temp comes down.

Good luck,

I'm not sure there's a problem here. You're getting a 24 degree drop from ambient with very high humidity - that's not all that bad. Try driving it on the highway for 15 minutes and see what happens. You won't get 40 degree vent temps until the interior of the car is cooled down and the blower speed slows down.

The high side pressure looks a bit low to me, but it's only 73 degrees. The MB manual specifies running the engine at 2000RPM for 10 minutes with the a/c on high and windows down - then check the pressures. The 124 shop manual has graphs showing the expected high and low side pressures at various temperate and humidity combinations.

Try pulling the glovebox and seeing if the recirc flap is closing all the way. You can see just a bit of it behind the HVAC box. Shine a flashlight in there and watch as you switch the a/c on and off. Your symptoms do sound a bit like good refrigeration but lacking 100% recirculated air.

- JimY

Try answering all the questions I asked....
Those were not random questions....

Before I did the pods airflow was very little and now feels stronger but still weaker than many other cars out there.

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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 )

Larry, the pressures were 29 nlow side, 148 high side, 73 deg ambient and 87% humidity when I had the hoses on last night. Blocking off the hose to the heater was my next move I was searching for a flat pressure plyers to do a temporary block but couldn't find one this morning so now I'm just going to block it with something else. When I did the pods I was having a problem with the recirc door but I fixed it and it was closing all the way, I'll check again.

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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'll check on that recirc door again.

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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 think I missed 2 of your questions, sorry. I did not install a new tx valve mainly due to the lack of time to replace it as it looks very hard to get to on this car, I think the 123 - 126 are easier to replace I remember seen it on my prior 300sd, I also fear the notorious evaporator on the 124's, I fear that while trying to undo the screws on the tx I might spring a leak on the evap from a weak spot that might have been there already from vibration since that's what must make them leak over time. The other thing question I think I missed was how I determined how long to pull a vacuum, from what I can see on the forum and from doing other cars one hour is good in most cases so I pulled a vac for 1.5 hours because my vacuum pump can not pull 30 inches, it only gets to 27. I also let it sit for about 40 min to make sure it held a vac and the needles did not budge at all.

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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 )

In warm weather and hour and a half of evacuation should be adequate.

Although I have not looked at a p/t chart, you high side sounds low to me. Are you running the engine at 1,500 ot 2,000 RPM? Is the sight glass clear?

Good luck,

Immediately prior to putting in the refrigerant you have now..... did you flush the system ?

I was running at about 1300 to 1400 rpms since I couldn't get somebody proficient enough in diesels to keep it steady at 1500 to 2000 you now they tend to take off after 1500 rpms specially the 603 with the alda adjusted, my cousin was doing it for me and he kept on letting it rev to over 3000 and the compressor would cycle off I guess from the evap getting too cold so I told him to keep it under 1500, I guess if it was hotter I would've gotten enough boiling at the evap to keep the comp from cycling. I figured since it was night time and the temp was only 73 then I wouldn't get so much head pressure. The sight glass was cristal clear, the bubbles would desappear after about 10 to 15 sec of the compressor coming back on. That's one of the things that's wierd, the evap does seem to get saturated and the compressor cycles off after a while just like is supposed to but I just dont get the right temp at the vent.

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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 )