My recently acquired 1980 240 D does not have a working air conditioner. I noticed that there was no drive belt on the compressor, so I installed one and turned on the compressor. A loud, screeching, metallic noise ensued, and before I could turn the compressor off, the belt broke.

A friend, who was watching the compressor, said the clutch engaged, and the pulley turned slowly until the belt died a quick, but smoky death.

My local air conditioning repairman checked the car and says that the system is currently charged, and that he could install a new pulley; however, he is not completely ready to rule out a bearing problem in the compressor itself. He suggested that, given the relative difference in price between the pulley and a new compressor/pulley combination, I might want to opt for the latter, as well as a new dryer and a retrofit to R134a.

I live outside New Orleans, and after searching the tech help archives, I’m concerned about whether this conversion is a good idea, given that it’s VERY humid here, and that I need lots of cool air to survive the summers. On the other hand, the compressor is 20 years old, and will certainly have to be replaced someday, and I will be forced to convert then anyway.

Does anyone have a suggestion as to my best course of action?

Thanks,
Ken Mitchell

Look for a gentleman named Larry Bible under these posts. he lives in Texas and is somewhat an AC expert. I'm undergoing the same thing with my 83 Mercedes Benz.(Freon 12 to R134)

Ken,

Well you found me, but I'm certainly no expert. However, we both live in climates that force us to be A/C experts. We know very well how to turn them on.

I have been through this firedrill several times. My experiences in changing to R134 have not been very good except for the price of the refrigerant being much lower. That's what drove me to change over a few.

I still have two vehicles that I have changed over, and they both leak. One is 16 years old and the other is 22 years old, so that in itself could have something to do with one or both leaking.

To start with, you need to determine where the problem is on your existing system. If it were mine, I think I would want to take off the belt(sounds like that's no problem right now) and see if the compressor will turn, or if it is frozen. I would think that if something was locked up enough to break a new belt, it would be the compressor not the idler. Use a socket on the center bolt to see if the compressor will turn. It should turn relatively easily. If it doesn't, I would expect that the compressor is locked up. I am assuming that when you refer to pulley, you're talking about the compressor clutch, not the idler pulley. Check the idler pulley while the belt is off by turning it with your hand. It should turn smooth and not have any bearing side play. The clutch is probably as expensive as the compressor, your A/C guy should be able to tell whether you need both.

Unless I'm mistaken, the '80 model has a York/Tecumseh type compressor. These are very good compressors, and are relatively inexpensive. But, I've never gotten the folks at the automotive A/C supply house to tell me that they will hold R134. I may not have gone to the right establishment. It could be that there are some that are rebuilt with different seals or something.

Another downside to using R134 is that Benzmac warned a few months ago about the oil drying out, and they need to be recharged with an oil change every two years, something I need to see to on mine. I think this is only on changed over systems, because of the different oil. Speaking of oil, if you do change to R134, there are two types of oil used in 134 systems, PAG and ester. Ester is what you must use, PAG is for systems that have never seen R12.

There is a loss of cooling capacity when changing over to R134. I hardly ever take short city hops, so the loss of capacity has not bothered me at all. If you take short hops, stoplight to stoplight, R134 may not be acceptable.

As far as changing only the clutch, I don't know if there is a possibility of ruining a new clutch if the compressor is locked up. I don't think that there is, but one of the pro's may have some warnings to offer.

Good luck,


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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

From your description of the event you have a locked up compressor. If the belt turned free until you turned the compressor on.

If you have a 1980 240D then you have an R-4 compressor which is so cheap anyway that it might be more costly to replace the clutch.

We have retrofitted hundreds of these cars and the results are fairly predictable. If you had good A/C before (which you won't know) then you probably won't tell the difference. Thermodynamically you should loose 5% efficiency. As it turns out the air flow over the large condenser on that model seems to keep that out of the equation. The larger determinant of good air on the 123 body seems to be the volume of air. There are multiple ways that reduced airflow through the facia ducts reduces volume on 123 body cars. This often is a greater effect to total cooling than the refrigeration capabilities.

We usually make new barrier hoses on that model when we retrofit with a new compressor so we haven't had the hoses eating the oil but that is an interesting note I picked up from benzmac. I will keep it underconsideration on other vehicles we do.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 04-05-2000).]

Same prob with my recently acquired 81 300D. No belt on compressor; compressor does not turn. Got new compressor (R4, $295) & dryer ($55) from ADSIT month or so ago. AC tech planning to replace units next couple of days or so (ASAP). I'm keeping R12.

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Wilton Strickland
Goldsboro, NC
91 350 SDL. 81 300D

Ken

I converted to R134 about two years ago after
my compressor went south. Haven't had any problems except one fitting was not tightened
down enough. Cost was under $1000 (included
new compressor, rcvr/dryer, 1 new hose, expansion valve, purging the system, etc). So far have been pleased with the cooling capability.




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Charlie Porter
'80 300SD 368K+ miles

Got new compressor (R4, $295) & dryer ($55) from ADSIT month or so ago.

I'd be glad to sell you new R-4s and driers for $268 and $43 all day long.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks, Steve, where were you when I needed you. I'll certainly try to keep you in mind for later - didn't know where to find you month or so ago; got taken, again, didn't I? Thanks for the info.

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Wilton Strickland
Goldsboro, NC
91 350 SDL. 81 300D

Keep in mind that I wouldn't sell that compressor for that price if I were installing it. We usually get around $350 retail. We also would not install that compressor for you if you had bought it mail-order.

A service shop will make a significant part of its operating overhead trough parts mark-up. A good independent will offer service and warrantee with that part that has got to be part of the job.

We do not install any customer supplied parts as we will not accept partially warranteeing a job. Our work is 100% warranteed no exceptions. If we installed a customer supplied part we could become involved in a warrantee dispute. By supplying the parts we are able to avoid that.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Steve,

Good points to keep in mind - thanks.

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Wilton Strickland
Goldsboro, NC
91 350 SDL. 81 300D