Questions on replacing A/C components
 

The A/C system in my 89 300TE has had a hose disconnected and since it is starting to get warm here in Houston I am thinking it is about time to get it sorted out.

Since it has been open what will I need to replace?

What will need to be done?

Since I don't know what has been done or replaced and everything looks original what should I be replacing?

Also...I will be replacing my heater core and figure since I am going to be doing this I might as well go a bit deeper and replace the evaporator...Would this be recommended? My wagon has 130,000 miles on it.

I basically need to come up with a list of things so I can come up with a game plan and list of things that I will need to be purchasing.

The receiver/dryer should be replaced. The evap is probably a good preventive step, but I can't say on your car how much extra work it is or the cots (I guess $200). Also, it would depend on how much longer you plan on keeping it.
Generally, you would get the system vacuum tested and that can help identify other leaks.

That's what I was looking for....I just wanted to know if I needed to replace the receiver/dryer and the evaporator.
I have seen where others tell the owner to not mess with the evaporator unless it is leaking....but I figure I am that far in and knowing my luck I will button everything up from the heater core install and a month later I will be needing to pull it all apart because the evaporator started leaking.....That logic just did not make much sense.

So replace the pieces that you mentioned, take her to an A/C shop and have em pull a vacuum so we can test if any lines are leaking.

Also, I have seen mentioned that people switching to R134 (they say the right way to do it) should go through and completely change their components, and I am guessing seals and hoses as well (I am not sure cannot find the posts I found).

Would this include a new compressor?

Do they make parts that are for use with R134 and replacing these would make the system better, cooler, or more efficient.

I do not mind using R12 and I am planning to go through whatever hoops I have to so I can buy the stuff....but I would rather have all my vehicles R134 so I can service them and not have to purchase a recovery machine for both refrigerants. I have a 65 Beetle that I would like to have A/C in, a 65 and 66 Mustang that are definitely getting A/C, a Jeep CJ-7 that is definitely getting A/C, and my Wife's new Saturn Vue that I would like to be able to work on....So getting a machine, training, and one type of refrigerant would make things so simple.

Keep the r12
 

r134 compatible seals and oil is the real issue with the conversion, so one does not change every component, including the compressor. Thorough flushing is critical, and always a new receiver/dryer of course.

No "they" don't.

With my experience with a converted TE done by the PO, I would make all efforts to stay with r12. The wagon is like a green house, and IMHO the MB A/C system is woefully undersized for double the load of a sedan.:(

Also, replace all of the vacuum control pods while the dash is out and the heater box open. I used the all aluminum ACM evaporator when I replaced one, and not the MB copper/aluminum part.

I've always wondered why you just can't get a condenser off of a 1995 E300/320 and install in the earlier models and go with r134a. If you are replacing the heater coil I would also recommend replacing the evap and all of the vacuum pods that are in the dash.

I don't think you have to go any deeper to replace the evaporator than the heater core; they are exactly the same job. And it's a big job, most folks here report ~20 hours of labor.

The evap used to be $200; I would expect it's gone up in the few years since I last looked at the price. Get one with a pre-installed expansion valve; you need to change it anyways and this will save you some time/trouble/effort.

Replace every o-ring in the system while you have it open. Brittle old o-rings are a common source of leaks.

The connections are not the same, so you'd need to do some custom hose work to get it plumbed. I also think the dual electric fans with the shroud are equally important to get good low speed cooling.

Ironically the later 124 cars that came with R-134a from the factory have among the better a/c systems I've experienced; they really make a lot of cold air, even a idle on a 100F day.

For my VW and Audi I was able to get expansion valves which were set up for R134a instead of R12. I'd imagine similar parts exist for the Mercedes.

-Jason

I agree with keeping the R12 system. This is how the car was designed.

Since you are changing the evaporator, you should change the expansion valve too, as the two are connected. If you didn´t want to change the evaporator, then you could always flush it out. Since the system has been open for a long time, you should flush the condenser too.

As long as everything is open, change the seals as well.

R12 must use mineral oil where 134 uses PAG oil.

Who is this "They" that I am mentioning and why don't they make the parts, Is is a conspiracy?

Sorry, this post got kinda long, I hope you stick with me.

Thanks 280EXRider...I new I forgot to ask something and your answer was to the question I forgot.

The pods are getting replaced, the heater core, all of the mentioned A/C components one of which is the all aluminum ACM evaporator with a pre-installed expansion valve, and all new seals.

So what about the hoses? Should I keep using them as long as there are no holes in them? If I do need new ones can't a local business make me some new ones at a much lower price than the ones available online.

If the piping and hoses are the only with the install, as mentioned above, I could find a local shop to make the necessary hoses.
Now, as far as the duel fans, What can be done to put dual fans in?

Also, If the later W124 cars came from the factory with R-134a and works good why can those parts be used, purchased, and made to work???


Hopefully this week I can find some time to do whatever needs to be done so I can purchase R12. I have been reading many threads and it does seem the way to go and I will probably go that route....but I like tinkering and the idea of making a different compressor working or pulling a system from one model year to another is just calling me (like I need another project)

Is it believed that if the early W124's (with r12 and completely stock) had dual fans that it could make a big difference in the cooling. From a comment above it seems like that was implied, but how many changes did they make to the A/C system.

Suggestions on what brands to use for the climate control components?

For the evaporator it was already recommended to use the ACM with the expansion valve installed. The other choice is a Rein shich I would have to buy the valve and install it myself.

For the condenser I have a choice between ACM, Behr, and Valeo but it looks like whether I use the Behr or Valeo will be dependent on the production date of my wagon.....Why would that matter?

For the Dryer I have the choice of ACM, Behr, or Hansa.

And for the heater core I have the choice of Behr or Nissens.

So can anyone make some recommendations? I thought the Behr parts would be more expensive but was surprised to see that some of the alternative brands were the more expensive ones.

shameless plug.
http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html
it's my a/c thread in DD, and your questions and answers could do well over there.
I'll keep an eye on the thread here, and copy good answers to mine.

Thank you for the link, I don't have time right now but I will be checking it out tonight.

and anytime a system is left open for much duration, the ENTIRE system should be flushed, and PRESSURE tested, not vacuum tested!!!
also, since it's impossible to properly flush a compressor, I recommend replacing it as well.
you CAN push fresh clean oil through a compressor by carefully filling the suction line, and turning the crank BY HAND SLOWLY until all the oil is pushed out of the compressor. it's usually better in the long run to just replace the compressor.

vetech, thank you for the added information.

What is used to flush the A/C system?

Are there compressors from other models that can be used? Not happy about having to replace it, but if it is best to do it then I will.