I picked up a Honda Prelude pretty economically with a non-working a/c system (r134). I replaced the compressor, condenser, dryer and expansion valve. Charged to the correct charge and the low side pressure was constantly swinging between 0 and 40 psi. Pulled the evap (takes less than 30 minutes on this model) and found the discharge line full of these little gray pellets, anywhere in size from a shot to a bb. In addition, they were in the expansion valve. Blew all this out and replaced the exp valve and put the system back together. Vacuumed down and charged and it is cooling somewhat. I am running about 40 psi on the suction side and around 180 on the discharge side. I'm not sure it is where it is supposed to be though and will probably pull the expansion valve/evaporator and take another look at them tomorrow afternoon. I'm getting a pretty good stream of condensate out of the drain. The cold seems to go away when I am running down the interstate and goes back to blowing as cold as it gets at idle. I'll bet I have evacuated and charged this system at least five times. One of the things that I am puzzled about is that I flushed and blew this whole system out prior to installing the new parts and I found the discharge line plugged up. I am thinking it is some kind of sealant chemical. Any thoughts/guidance will be appreciated.

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Jim

I would say those pellets are from the old filter drier. We cut one open from a Honda at the beginning of the sommer and thats what we found. I remember reading an article that said that was a problem on honda's.
Your pressures sound great and should cool just fine. has someone bypassed the evap temp sensor on this thing? If so the evaporator could be icing up and preventing airflow. That would definatly kill coolling performance.
Did you weigh in the correct charge? Just a thought bin bit in the ass more than once just charging till it "looks good"
Post back with ambient temp and humidity

I did weigh in the correct charge.
Ambient is about 97 dF with 80% humidity.

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Jim

After a thorough analysis of the sample it looks like the dryer went bad. Got another one coming and will install it tomorrow. My plans are to pull the evap and blow through the discharge side between the dryer and evap while it is apart. I drove it to work and it was coming and going today. At certain rpms it blows cold like it is supposed to.

I will say it is alot less pia to get parts for the Mercedes than the Honda.

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Jim

I have a 5th generation, and yours is a 4th, but I have the FSM for mine. If you need/want anything out of it, I can scan whatever you need.

Also, if you wanted the FSM for yours, they are made by helm ( www.helminc.com ). Mine was $62 I think.

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1984 300TD

Could you please post your a/c pressures after the fix. It seems to me the high side is low for your ambient temp but your not low on charge. It seems to me one of the most important things a mechanic can do is look at data from good running systems so you can identify bad systems/ A/C electrical transmission whatever.
Make sure you blow out the outside of your condensor and radiator. It's amazing howmany cars I see with a/c problems and thats all that is wrong. I know that would give really high, high side pressures but it doesnt hurt.

I hooked the gauges up to a '94 Honda DelSol that was blowing cold under the same ambient conditions and got 225 hi, 40 lo on it.

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Jim

Went through it again, pulled evap and dryer, blew out the line between the dryer and evaporator, replaced the dryer and am vacuuming it down as this is being typed. There were some more of those little pellets in the system and expansion valve that I cleaned out. I sure hope that is all of those bothersome little sob's.

I finally pulled the passenger side air bag to allow easier removal/installation of the evaporator. I should have done it that way the first time. Oh well, I am on somewhat of a learning curve on this car.


Update - just got back from a test drive. I have it as good as I am going to get it. Man, what an ordeal.

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Jim

I cleaned out the discharge line between the dryer and evaporator two times this past weekend. This involves removing/installing the evaporator. I blew it out while I had it outside the car. I am still getting those little balls in the expansion valve. I'm thinking there can't be that much more of them. From idle up to around 70 mph the system does fine. The cooling falls off past about 70. My theory is that the higer rpm pressures force those little balls into the expansion valve where they accumulate at the end of the discharge pipe. I don't have a clue where they are coming from but they sure are a pia to get rid of. I am considering replacing the discharge line from the dryer to the evaporator. I have already picked up a new evaporator and will install it this coming weekend.

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Jim

you might consider a condensor as well there is no way to get those little balls out of it. The balls are from the filter drier which has come apart.
I still dont know why the high side is so low 225-250 seems right and is what I have seen all summer on good working 134 systems. I threw the guages on a camry today about 95 in the shop. 250 high side 35 low side at idle. on the test drive 38 deg outlet temp.

I replaced the condenser when I replaced the compressor. In addition, I flushed the condenser out this last time and did not see any balls come out of it. I will install the new evaporator this coming weekend. The more I look at the arrangment/layout of the evap the more I suspect it is partially plugged. Something is reducing the flow at higher rpm/pressure.

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Jim

I talked to my boss today ( he's a good a/c man) when I told him about the pressures he said it sounds like a weak compressor and to me that makes sence. You dont have enough high side pressure. Too low high side pressure wont turn the refrigerant into a liquid, So your trying too cool vith vapor only. I think to prove this you can soak the condensor with a garden hose and measure the outlet temp. It should drop to where it should be. Let me know what happens.

Low side pressure looks good
high side too low

I'll pick up another compressor to try. I am going to install a new evaporator this weekend too.

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Jim

Man, this thread reads like a horror story. I hope to never encounter this on any of my cars!

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

reads like technical issue to me. Think how fast this could be solved if we could look each other in eye and actually both touch the car as its running. When you get stumped you can immediatly turn to someone else in the shop for an opinion. Bet you he's gonna be hangin meat in this thing by the weekend!