Uh oh, AC work coming up soon.
 

The Delco AC compressor in my 300D has just about ate it. The bearings are frozen and it won't spin at all. The belt was making a terrible squealing noise and I smelled burning rubber (not from the tires this time) so I cut that belt. This was at the end of last summer. I figured I could live until next summer without AC. Well, with some nice hot California weather approaching, it's time to get that AC going again.

Being silly, I bought a new receiver dryer, AC compressor, and expansion valve. I figured I could install it by myself, but it doesn't seem likely. The compressor is in a really awkward location, so maybe it's best left up to someone who knows what the heck they're doing. The best price quote I got was $400 for labor, and figure another $100 or so for a fresh charge of freon. And this was from one of the FEW places that would even touch parts that I bought. Should I keep looking, or does this sound like a fair deal?

Oh, if anyone in the Bay Area would like to help, I wouldn't mind! :)

Since you already have purchased all the parts the price ($400-$500) sounds pretty much in line.

I agree - $400 is not a bad price.

The compressor is not as hard to remove as it would first appear - if I was not 3,000 miles away I would glady give you a hand with it.....

Tim

AC
 

The compressor is pretty easy to replace, as are the rec/drier and exp. valve. Put the front drivers side up on a ramp or jack stand and you will have plenty of room to access from underneath.

Just a note....you may have leaks on hoses (if original, they are 20 years old). Check all threaded and compression fittings for signs of oil leakage from the system...if oil is leaking, so is freon. While it does get pricey, if you plan on running the car for several more years and want AC, this is a good time to change hoses. The most expensive hoses are the ones with the bent metal components. To save money, you can re-use the metal parts (assuming no damage) .... a good AC shop can rebuild the hoses by brazing on crimp fittings and replacing the rubber sections...you need to find a shop with tube brazing and crimping tools. (I found a place to do this after I bought new hoses!) I bought aftermarket AC hoses at a significant savings...they are no different than OE. Also note that all new hoses will be R134 compatible.

Also check your condenser..this sits right up in front of the car and takes the brunt of beating from road sand and debris, especially at the lower front. If the fins are all beat up and there is a lot of corrosion, you should probably replace it.

Chances are the evaporator is ok since it is protected in the dash. Its a good idea to take a look....remove the blower fan housing (easy) and use a flashlight and little mirror to view inside the front of the evaporator....if you find dirt and debris in there, you may have serious corrosion. Its more likely that you will see a nice clean unit.

Are you going to convert to R134 or stay with R112? If you are going to stay with 112 you will be fine. If you are going to convert, I can offer some suggestions regarding system mods and flushing. I converted to R134 and I am very happy with the performance, although probably not as good as R112. But much cheaper from here on for recharges.


Good luck.

Mark

Freeze 12...
 

Just arrived back on the east coast from Texas driving a 300CD bought from a fellow poster. One nice thing is that the AC seems to blow cold, and the former owner replaced the old refrigerant witn something called Freeze 12. Don't know what the deal is, but this is the first time I've ever been chilled in a diesel Mercedes.

You might look into this Freeze 12 stuff. Good luck.

Mark, many of us are studying up on the 134 conversion right now.... so we want to know what you suggest for the "system mods and flushing".. Thanks,Greg

I agree with TimFreeh and others, this compressor is not that tough.

Jim B,

I would HIGHLY recommend that you get the Freeze 12 out of your new (to you) car. Freeze 12 is highly flammable. If the compressor were to seize and make a spark, you and your family will be inside a car bomb. This stuff should be made more illegal than R12.

I would blow the charge, thoroughly flush the system, replace the filter-drier and assuming it is an R4 Delco compressor, drain as much oil as you can get out of the compressor and put 6 oz. of Texaco Ester oil in the compressor, reassemble and charge it with r134.

Please don't take any chances with this stuff.

Best of luck,

In Boston or Washington DC, I expect that r134 will work out pretty good. If you are in Texas or Florida, etc, you will lose enough capacity that you will be uncomfortable most of the time unless you drive only long trips. You can regain the lost capacity from the conversion by adding about 20% more condensor capacity. I'm not sure if a condensor that large will fit in the location available.

If you are converting, it's nice to change to barrier hoses, but not usually totally necessary. The main thing is to flush the system, use compatible o-rings, an r134 drier and drain the oil out of the compresser. You then put in r134 compatible oil. If you have COMPLETELY flushed the system in the conversion, you can use PAG oil. If you're taking the shortcut and not flushing and replacing the drier, you will be forced to use ester oil to be compatible with the left over mineral oil. Oh yes, go to www.acsource.com and get the brass adapter fittings to go from 1/4" inverted flare to the bayonet type r134 fittings.

A great source of information is the bulletin board at www.aircondition.com, the best source for auto a/c goods that I've found www.acsource.com.

BTW, for flushing, you can get a cannister with air chuck and schrader valve that lets you pour in the flush, pressurize the cannister through the shrader valve, then spray with the spray chuck throught the opened components. When resealing everything, use the green r134 compatible o-rings. You can get a kit of o-rings and special glandular lubricant for $20 or so. It is well worth it.

Best of luck,

Ok, Larry, I have been itching for an excuse to make my own condensor...

How can I design it so that it is one of these 'parallel flow ' condensors.. I have the contrucion technique down...

Is this like the change in radiators from the up down flow to crossflow ?

are there any hidden things inside a condensor that I need to know about... ?

Of course , in addition to having more capacity mine will be made from stouter stuff...copper and brass.... Greg

system mods for R134
 

I dont consider myself an "expert", but at the time I did the AC work on my 85 300D, I was skeptical about the effectiveness of R134, and made various decisions to maximize the effectiveness of R134. I cant guarentee that other configurations wouldnt work as well, or if all of the "mods" i did were necessary. Here is what I did:

Vertually every component of the AC system, EXCEPT the evaporator, was replaced with new stuff. So the evaporator was the only thing that needed flushing. I intended to use PAG..the prefferred lubricant for R134, but in order to use this, you must flush all mineral oil out of the system. Otherwise you need to use ester as the lubricant.

I flushed with lacquer thinner, and coleman fuel (extremely volatile (and flammable) in order to ensure easy removal). Dont use low volatile mineral spirits....more difficult to remove.

To flush, I drilled out the old expansion valve and reconnected to the evaporator (using it as a service connection) and the two old hoses leading to the engine compartment, and flushed via these hoses...pour in a cup of solvent with a funnel and blow out with compressed air. Flush forward and backward several times, blow out both ways, then pump air through over night for a couple nights to ensure removal of solvent. Done.

All AC components (except evaporator) were replaced with either OE equipment (NEW R4 compressor, exp. valve, rec.drier) or aftermarket (most hoses and condenser). The condenser I used was an aftermarket universal parralel flow condenser, mounted with "L" brackets....I used the biggest one I could fit in. One of the limiting factors in using R134 is the capacity to condense, so I went with a parralel flow unit ensuring good condensing and low "low side" pressures.

Because the fittings on the condenser were not the same as OE, I had the two hoses that connect to the condenser custom made to fit.

Another mod was: I wired the aux. fan via a relay to the compressor, so that whenever the compressor is on, the aux fan goes on.

ANother mod: since the temp/pressure profile for R134 is different from R12, the temp cutoff switch on the rec./drier would not necessarily work properly, so I place of the OE low pressure cutoff switch (also on the rec./drier) I replaced it with a hi-low pressure cutoff switch (I forgot the pressure cutoff points)....this gives me an appropriate high pressure safety cutoff instead of a temp cutoff designed for R12 (this is only a safety feature, and does not effect performance).

The only performance-related mods were the par. flow condenser, and wiring the aux. fan to engage when compressor goes on.

I put in 5 3/4 oz. high visc. PAG into the compressor when I installed it. I lubricated all green o rings with mineral oil. Brought to AC shop, evacuated system under vacuum, then charged with 24 oz. R-134.

Center vent temps go down to 39 deg. F, when outdoor temps are in 90s, and fairly high humidity. When humidity is at 100%, center vent temps go down to 43-45 deg. F.

A major limiting factor in this AC system is the relatively small evaporator. Its just not big enough to blow snow like the good AC systems in good old american cars!!! It seems that the German philosophy here was similar to other systems (radio, dash lights, AC....not necessities and not safety features, therefore underdesigned)

Good Luck,

Mark

I converted an 81 240D to R134 two years ago. I did not do as complete a job as MarkM but I basically took a similar route.

Larry is correct R134 is fine for service in northern climates - it just seems like up here the sun does not hit as hard as it does in Texas and the southwest. I'm not sure if its the humidity or pollution in the air but you guys down south are in a totally different league than those of us north of the mason-dixon line. I know it the same old sun but down there it feels totally different to me.

I get center vent temps in the mid 40's - the only thing the system does not do too well is cool things down when you are going for a short (5-10 minute) drive. For anything else it seems to work fine. I think R134 in a W123 chassis would work fine in northern California.

Tim

What does it take?
 

I think I want to go to R134, but I know it is not as cold as R12. And even the R12 I have isn't as cold as I would like on hot days. Would putting a stronger compressor make it colder? What allows max performance in these cars?

on acsource.com or aircondition.com they talk about a VOV replacement for the expansion valve that is stock...it does not list MB ... but some of the components on some of the MB are GM , etc, right ?

Can one of these be used in the MB system ?

they have a heavy duty one that is specifically listed for places like Houston.... using 134a ..they do show it for a lot of normal cars.... anyone know what I would have to do to the evaporator to fit this to it ?

To: Larry Bible

According to the following web site, it claims Freez 12 is non-flammable and contains no CFC's.

http://www.freeze12.com/

I did about 2 minutes of digging on the web and found that Freeze-12 is 80% R134a. The remainder is either R124 or R142. At any rate, it's pretty darn inert and certainly inflammable. Whether it works, I don't know, don't care. I'd just do an R-134a conversion before using this stuff - it's not that hard to flush the mineral oil out of the system.

Larry may be thinking of an R-12 substitute which used to be sold here. OZ-12 was the name. It was pure hydrocarbon - a mixture of propane & isobutane - about 60/40 as I recall. Cools fine, and it's great at carrying mineral oil through the system. It is a wee bit flammable, though. Since the EPA banned hydrocarbon refrigerants in mobile applications, I doubt anything like it can be found anymore. Nothing out there has more than ~2% hyrdrocabons; not enough to worry about, in my opinion.

Still, there are hackers over at aircondition.com rolling their own refrigerant out of grill gas & camp stove fuel. I'm not about to use hydrocarbons, but you gotta love the price - about $0.50 for a full charge...