no AC, any advice - PeachParts Mercedes-Benz Forum

mzsmbs · #1 05-12-2004, 02:08 AM

Ok, it's getting hot here and the AC is just not doing it. Since the AC belt wasn't on the car when I bought it I put one on the other day to try out the system. Well the air is not cold; felt kind of about the same as the outside so wanted to get some ideas from you guys on how I should proceed. I am guessing the system was designed for R12. I saw 134a conversion kit for $35 but I read that it just doesn't compare. So, can I still get R12 somewhere? If not how do I go about converting to 134a? Is it hard to do or is it a DYI job.
Any help would be appreciated. I don't know anything about AC but sure would like to have it working. It's only gonna get hotter.
Thanks and appreciate your help.

stejm · #2 05-12-2004, 03:05 AM

Do not, repeat, do not even consider the conversion kit. Take your car to a local Mercedes mechanic and ask them to check the system. The belt was off my 250 and I was blowing ambient air, so I called around town and found an indy that stocked R12. Took me a while, and word of mouth, but after I passed the test they reconnected the belt, charged and pressure tested the system, and I was blowing 41 in the vents after the day was done.

Converting requires extensive knowledge of AC systems, tools, the luck of Yahweh if you're a newbie, and several cases of beer to dull the pain of a failed operation.

Make sure your AC support bracket (no idea what it's called) has all the bolts connected. My York shook like the San Andreas on a testy afternoon before I discovered I was missing a bolt. I mean, the lads in the lowriders on Sunset were intimidated by my bouncing car due to the internal movements of the trusty York.

Granted, you might have a leak, and if so, expect to pay major $$$. The hoses are apparently constructed from rare earth metals only mined once a year in the dead of night.

The conversion kits will create Black Death... Don't do it.

ctaylor738 · #3 05-12-2004, 08:22 AM

The table stakes to get a long-dormant AC system working are to charge it with enough R12 to get the compressor to work, with dye added to check for leaks. If there are no leaks and the compressor works, then they would probably pull the R12 out, replace the dryer bottle and evacuate and fully charge the system. If there are leaks or other problems, the cost will make you think about how much you really want AC.

The hoses can be rebuilt, using the fittings for a fraction of the price of new ones, but you need to find a shop that will work with you on this.

BTW - the PO converted my 280C to R134 in 2000 and it still works very well. The total cost was $507, which included a new dryer bottle, a rebuilt hose, a pressure switch, and schraeder valve.

#4 05-12-2004, 12:32 PM

Was the replacement of such parts necessary to convert your system to R134a?

I have the standard York system that appears to be excellent shape but blows non-cooled air, after being dormant for some time. If all the components are found to be in good shape, is a conversion simple? I have a local guy who does A/C work all the time (non-mercedes) and he said to find out if my system is easily converted.

Thanks
Will

ctaylor738 · #5 05-12-2004, 12:54 PM

There are a lot of posts on this on the Tech Forum. The 123 cars have the same basic system with the York compressor.

My understanding is that you need to change the schraeder valve and pressure sensor to get the system to cool well. The dryer gets changed to get rid of the old oil. You need to drain the compressor and use ester oil.

But if you look at the posts, you will see that opinions on what you need to do are all over the map.

j9fd3s · #6 05-12-2004, 04:02 PM

what you need to change depends on whats bad and who's working on it.

for example the tv show 'crank n chrome' aka 'two guys garage' aka 'shadetree mechanic' their ac diagnonsis was to change everything except the evaporator....

you should at least replace the reciever drier, part of its job is to absorb moisture, and if the system is open (leaky) then its full

Tomguy · #7 05-12-2004, 05:40 PM

Charging an R12 may be difficult because it's hard to find, you need to leak test, etc... sounds expensive... BUT it's cheaper than R134a by light-years! If your system leaks you need to get it fixed for R134a anyway, it runs higher pressure.

The whole system needs to be flushed thoroughly because the oils used with 134a and 12 are incompatible.

Then you need to change out components - dryer, valve(s), and pressure sensor(s). Once that's done, you need to fill with R134a and ester oil. The refridgerant is a crapload cheaper and easier to buy, but it's a lot more of a PITA to convert the system than it's worth.

The original MB owner's manual for my '72 actually says to run the AC (every month?) even in the winter to keep the system at optimum levels. I assume this is to prevent pressure-equalization and leaks/backflow in the system.

I need to get mine working soon, too. Belt's off it but I know it needs a charge - it didn't even blow cold in the winter!

I won't put up with the cost and/or hassle of conversion - I definetly don't want/need to do all that myself, and I don't have the cash to pay someone else.

Properly maintained, your system should hold a charge for over 10 years - my Jeep's AC system (R12 or R43?) hasn't been charged once, and it's a '92 (though I think it might need a little, just for better efficiency)

mzsmbs · #8 05-12-2004, 07:08 PM

Sure sound complicated. Darn.. I'm gonna have to look into it further. Thanks for all your commments. I'll check in with this thread from time to time and I'll let you all know what I decide to do if anything.