W126 300SE AC Compressor

[Rose Chap]

I’d like to pick the brains of the knowledgeable types on here about a particular problem with the AC on my W126 300SE.

A few weeks ago a horrible noise started from under the bonnet. Subsequent investigation by a mechanic revealed this to be a faulty AC compressor, so this was removed and a shorter belt installed so the car ran as normal – just without AC. A replacement compressor was ordered, though this didn’t fit the mounting position available.

Even more further investigation revealed that whilst my 300SE had AC from new, it had at some point since being built in 1989 and my buying it in May, the AC compressor had been replaced with one compatible with R134a, but the compressor in question was not an OEM part, and to make it fit had been mounted onto a bracket. Attempts to source a direct replacement AC compressor have not been successful – apparently the unit isn’t made any more.

Once this was figured out, my tame mechanic found that the bracket holding the AC compressor was removable, leaving holes in the engine casing(? – not sure if my terminology is right here but hopefully you understand my point) that presumably the ‘proper’ (Mercedes) AC compressor would bolt into.

Unfortunately, there is confusion about what AC compressor should go on. Would one from a W124 300E work? Does it have to be from a W126? Is it the engine that dictates the AC compressor? The model year? I’ve seen a few available second hand and from spare parts websites, but I don’t want to order the wrong one.

Also, how hard is it to fit the replacement compressor? Hopefully it’s just a case of bolting it on, fitting the right poly V belt, reconnecting the AC pipes and getting it recharged. Am I being hugely naive here or is it really that simple?

All help gratefully received!

RC

 

[219]

I'm a little shocked that there might be a need to 'replace the compressor with one compatible with R134a' .

I was looking at getting the ac on my 500SEL converted ( still the old R12 system and has not been working since I got the car almost a year ago - but not the highest priority job ) - when I enquired about it at a local indy I was told 'system has to be evacuated , all seals changed , new receiver/drier fitted' ; then there 'might' be other problems that could come to light once system is charged ie condenser . There was no mention whatsoever about changing the compressor . Since they weren't even prepared to give me 'best case/worst case' ballpark figures - I was not about to hand over the car with a blank cheque . I've since found a couple of local specialist air con engineers who come to your house , so I'll try one of them next time - maybe during the winter when I imagine they'll be less busy ( possibly cheaper ? ) .

To come back to your original question - I don't know , but besides my 500 , I have a pal with a W126 280SE which has air con - I'll compare his compressor with mine , if it looks the same / has the same part no then it is probably a reasonable guess that all W126's will use the same compressor . There is a 300SE breaking in a yard near me , but without air con - I just got the alterator out of it for my 190E 2.6 and the passenger seat base to fix my sagging driver's seat , plus a few other small parts - but the car is still substantially complete , and this yard seems to get 126's in from time to time ( this is the 2nd one I've seen there ) . They also seem to get quite a few 'interesting' cars in - the corner where the 126 was also had a Rover SD1 , MG Midget , Beetle convertible , Morris 1000 , Cavalier Convertible plus a few other less common cars .

The Russian website may be helpful to show which other models use the same pump .

 

[jaymanek]

Do you have all the original buttons inside the car?

You dont need to change the compressor for R134. probably some other reason it was changed,,

I have a used compressor here from a 380 SEC that would probably fit?

 

[Rose Chap]

Many thanks for the excellent tips so far.

The button on the dash is original and matches exactly the button location and operation in the manual.

R134a was written on the old compressor so maybe it was part of a conversion to R134a undertaken during the cars life?

 

[219]

Ah !

When a conversion to R134a is carried out , the engineer is supposed to put stickers on near the ports to indicate that the conversion has been carried out . Maybe this is what you saw ?

Mine just has a red sticker , with 'R12' amongst the text , on the landing panel .

 

[Rose Chap]

Do you have all the original buttons inside the car?

You dont need to change the compressor for R134. probably some other reason it was changed,,

I have a used compressor here from a 380 SEC that would probably fit?

Sounds good Jay, I'm interested. What's the best way to go from here?

 

[jaymanek]

Well if you could pm me your chassis number ill check that the part I have is the same.