1987 W124 air conditioner problem

[260E]

Hey everybody
I'm having trouble getting my a/c compressor to work.
In the beginning of this summer, I checked the refrigerant at an independant shop, and had to add some, because of a leak I'd rather not look into (all it takes is a refrigerant refill once a year, I think it's simpler than spending time to look for the leak).

Once the refrigerant was refilled, I tried to use the air conditionner. The compressor started, worked for a minute (really, a minute, 90 seconds max) then got turned off, never to start again.
The following day, the same problem occured: the car gets cold for a minute, then the compressor stops.

I'm guessing it is a Klima relay or sensor related issue, but I don't know where to start looking.

Does any of u have the wiring diagrams of the 260E W124 1987 air conditionning system, or a schematic of its klima relay [here's what I copied off the relay when i took it out:
002 545 13 05 (I guess this is the number)
6ZYL
Siemens 5WK2 266
12V]

I am asking for the Klima relay drawing in order to be able to bypass it, or at least determine what sensor is faulty if that is the case (if I know how it's wired, and where the pins are going, maybe I can figure out where the problem is)


any help would be greatly appreciated.

 

[219]

Hmmm , while I am no expert on a/c , with only a rudimentary knowledge of these systems , I wonder if you have had the correct gas put in for your system ?

If you had it topped up this year , you would only have been able to get R134a , but I wonder if your system was not designed for the older R12 gas ? My 1986 500SEL and '84 280SE have R12 systems which will need conversion . Since your car is about the same age , I wonder which gas your system was designed for and whether it has subsequently been converted ?

Trouble is , if you just put R134 into an R12 system without having any other work done , the new gas can damage some of the seals and hoses in the system , giving rise to leaks . It is possible to have a UV dye added along with the gas , which will show up the location of any leaks under a UV lamp - this might be a good place to start . There should be a sticker under the bonnet indicating which gas is suitable , if the system has been modified , there should be new stickers indicating this - in any case the ports for each type of gas are different , but some people have been known to just screw on adaptors .....

There is a pressure switch , which will stop the clutch from engaging the compressor if there is insufficient gas pressure in the system - given that you already had a leak this is quite possible , and even with a top up , you may already have lost gas pressure . Leaks do , unfortunately , have a way of going from 'slight' to 'major' overnight and are never going to get any better , so I'd be inclined to start with a pressure test and , if as is likely the pressure is down , add some dye to pinpoint the leak . You might be lucky and find the leak is somewhere easy to fix , but even it it isn't , you will at least know what the problem is .

The 'sensors' , I believe , are just pressure switches , so should either meter out as open circuit or closed .


Good luck .

 

[Howard]

Don't know if the w124 systems are the same but on the w208s etc , when the system senses a loss of pressure it disengages the clutch to the compressor to avoid damage to the system.

Yours might just be on the cusp of the level that triggers it therefore it runs for a minute and then disengages the clutch ?

Perhaps your leak has got bigger ? searching for it is easy , the AC place will pump a dye into the system and then look for where it is exiting under your bonnet with a UV light , job done.

 

[balge]

hi
assuming this is original equipment a/c? Did a bit of research, as my 300TD has an aftermarket Diavia system, but if yours actually has a klima relay it must be stock?
Attached is a test procedure for the klima (its not really a relay, its an ECU....ask me how I know) should help locate the problem, and a pinout for the klima - its a US market I think but probably the same? Basically all the sensors inputting the klima have to be right before it will turn a/c on and if all the sensors are right and a/c still doesn't come on then its the klima...and you're in a world of pain

This is as near as I got to a wiring diagram,

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1987/260E/WIRING DIAGRAMS/

might help!

cheers!

 

[balge]

pinout

hmm, seem to have left out the pinout diagram, try again!


cheers!

 

[260E]

Thank you all for your help!
@Pontoneer: thank you but this isn't the problem, I have an R12 system that I recharged with R12 compatible refrigerant
I checked refrigerant, seems adequate, so the leak could not have caused the problem.

As for the pressure switch issue, I wanna thank Howard and balge for ur advice. I'm gonna use the testing layout you gave me (the .doc file) first thing tomorrow, I'll tell you about the results.

 

[balge]

No worries, it took me ages to sort out all that, then I worked out it wasn't really relevant, so it's good to see someone else getting use out of it!
Any luck so far?

cheers!
balge

 

[bolide]

Have you got the correct weight of gas in the system? If you have, are the pressure switches working OK?

These are simple systems and a test light or voltmeter will find most faults. Look at corroded fuses too

Nick Froome
the independent Mercedes Estate specialists

 

[giovanni.t1973]

I have a mercedes 250E (w124 year 1989).
Do you have the AC system wiring diagram?
Please help me
Thank you

 

[grober]

This might help its for w201 models but likely to be similar. http://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/20003.pdf

 

[JohnSA]

W124 Air con problem

I have a 1989 W124 200, the aircon on which has stopped working. The light on the selector illuminates but the compressor does'nt run.The system has recently been topped up and tested for leaks. I have found a ceramic covered resistor(?) marked BERU 0110610 030 just behind the left headlight unit. The ceramic covering has disintegrated. WHAT IS THIS UNIT AND COULD THIS BE THE PROBLEM?

 

[94mattda]

Hi, I have a similar problem where I have had my A/C recharged at one garage and it was blowing ice cold air. My car is a 1995 W124 E220 Coupe. Next day it was not cold! I took the car to an MB specialist who after checking advised there was no refrigerant, they then pressurised and vacuumed the system and it passed both tests with no loss in pressure in over an hour.. then nitrogen with oil and dye was added and again no loss of pressure and no dye could be found. The car was recharged again with refrigerant and I had ice cold air, next day no gas left and no cool air. There must be a leak abut after a second search with due they still cannot find anything. Any ideas where it may leak that’s hard to see or can’t be seen?

 

[alabbasi]

Put gauges on it. They may have over charged it

 

[94mattda]

Put gauges on it. They may have over charged it

Finally found the leak from the compressor, hard to see originally but finally got it. Will replace compressor with new or remanufactured if I can find one as MB main dealers don’t stock it any longer.

 

[alabbasi]

At least for US cars, the OE compressor is a denso 471-1224 which sells for about $250 US.
Check the part # on the compressor itself, you might be able to find an aftermarket alternative for less

 

[94mattda]

Thanks will do, seem some new ones online, going to stay away from second hand as don’t know the condition, apparently need to change the drier st the same time.