Whats the dash look like?

I believe 79 was the change over year....early had the huge york in front of the air cleaner....late 79 had the small compressor under the power steering pump..

 

It has a single A/C dial in the center, I'm not sure if it's the later design.

 

That is the early style. The later 240D had a wheel similar to the CCU on the 300D. Your car should have had the york compressor like this.

 

79 was a split year for a/c compressors - early used the yorks and late used the R4. I have had both. My 80 240d has the dash like in the picture with a R4 compressor. I have a 79 with a R4 and a 79 with a york. The block has an 'extra' hole if the R4 compressor was/could be used. look under the P/S pump and see if that hole is there. Many of our cars have had engines replaced and some shops/owners un-knowingly installed the wrong blocks for R4 compressors.

 

Looks like mine is under the power steering pump. All this time and I never noticed, I'm actually a bit disappointed in myself. It spins freely, but no belt, so I'll pick one of those up soon. So, this is an R4 compressor?

Thanks everyone for the help! You guys are awesome!

 

yep you have the R4 compressor. Make sure not just the pulley spins freely, but that the magnetic clutch plate in the front of the compressor [which turns the 'innards'] is spinning with just light friction. Its usually the compressor that fails not the pulley and bearing. If the paint on the pulley or plate is yellow in colour the compressor is bad.

 

Good to know, I'll check it after work tomorrow. I looked these up on eBay, ouch! Just in case it's bad, any chance a compressor from a 1980 380SEL (W126) would be the same? I can get one for $30 that way. Also, can the compressor be rebuilt without special tools?

 

Might be wiser, just to take the car into an ac shop and see what they would charge to diagnose the system..

 

I would if it weren't for having no money and getting ready to go on a three week recovery after surgery. That means any money I make for a while will be used for catching up :crybaby2: On the plus side, after surgery I can quit this minimum wage job and start making money again

So, for now, I'll have to do stuff like this on my own and hope for the best.

 

About the best pictorial I've seen:

How to Repair Your A

 

This is going to help a lot, thanks!

 

personally, i would NEVER consider a used R4 compressor, nor would i consider rebuilding one either. the 'experts' who rebuild these compressors have issues putting them together so they last. it's an aluminum cased unit which is hard to press back together without damaging the unit. i learned this the hard way. the tutorial is great uberwasser, thanks for posting it. the expression 'pay-me-now--or-pay-me-later' applies here. a few extra dollars spent here is well worth the price of doing it a second time. i have found places that offer 2 year warranties, look around...

 

Well, there is a bit more than a few dollars between $260(minimum) and $30-$50. I could buy five used compressors and swap them out when they go bad compared to a new one that could go bad anyway.

 

here are two listings... one for $170 , the other for $120 shipped. how much is your time worth not to mention the freon and oil and the cost of flushing the system again and again...


80 1980 Mercedes 240D A/C Compressor - Climate Control - Four Seasons - PartsGeek

78 79 80 81 82 83 84 85 Mercedes 300D 300CD Compressor | eBay

 

Don't give up on your R4 yet. Since it was last running w/ freon and mineral oil, it shouldn't have degraded by sitting, as long as water didn't get inside. If there is still refrigerant pressure inside, even better. You can spin the inner shaft by hand and feel at the high-pressure outlet for pressure w/ your thumb and for suction at the low side. You would have to break a tube fitting open for that, but best to change the O-rings on those fittings anyway.

The AC belt on my 1984 had broken a few years ago, so I assumed the compressor had seized, though I could spin it by hand. It still had some pressure so I kept the filter/drier, poured in 4 oz of Duracool's "Oil Chill" PAO 68 (to add to the PAG oil I assume was there, had been converted to R-134A), charged w/ Duracool refrigerant and have been running cool for over a month.

 

Good to know, thanks. Just noticed, is my control for the earlier compressor? Will it still work on the R4.

 

Can't think of any reason why it would not work. I haven't seen any compressor, even on the latest cars, that isn't a simple +12 V "actuate clutch" wire. Often, they ground the return to the body of the compressor (bad ground was for my 82 Aries "no AC"), but M-B went better and added a dedicated ground wire (brn). There is a pressure switch on the filter/drier that enables the clutch, but that would work for any AC compressor. Check the basics first, like that the connector didn't fall off the clutch, measure the resistance of the clutch, connect 12 V to it w/ jumpers and see if it actuates, bypass pressure switch, etc.