I have a 1987 560 SEL 230,000 miles. The air conditioning does not work well at idle or low RPMs. When driving at 40 - 50 mph the it does a reasonable job. Other than refridgerant what should I look at?

 

The aux fan. At speed you have air moving across the condenser at idle the aux fan should be pulling air. also might need to clean the condenser as bugs and road grime can clog it.

 

I've looked at the auxillary fan and it does not run at all. The fan wheel turns freely, but I can not get it to run. The fuse for the Auxillary Fan is good, I checked for voltage at the connector while the engine was running anf the A/C on. No voltage. I'm trying to chase down the control circuit, but the circuit diagram I have is very grainy and hard to read. I'm trying to locate Relay K9 - Auxillary Fan Relay, K10 - Auxillary Fan Preresistor Relay and R15 - Auxillary Fan Preresister Group. Any suggestions. What are the conditions for the Auxillary Fan to run?

Thanks for any help

 

Put 12 volts to the fan to verify it works but you checked for voltage and there was none so it is probably ok. I had the exact same problem. It was the switch at the receiver/drier. With the A/C on I shorted the wires coming from the switch and the fan came on. I replaced the switch http://www.autopartswarehouse.com/sk...2.html#reviews Only problem was I had to pump it down and then recharge the A/C. Luckily I have a vacuum pump. Now it works

 

I forgot to mention normal operation. The fan comes on when the vehicle exceeds 105C or when the pressure reaches a preset in the A/C at the receiver drier. Your problem is poor A/C performance at low speed so the pressure switch isn't turning on the AUX fan.

 

Thanks for the advise, the switch was bad. Jumpered it out and the auxillary fan runs like a champ. The cooling is still not as good as it once was. Is there a test to verify the electromagnitic clutch on the compressor is engaged?

 

You can visually see the clutch engage. When engaged the entire thing rotates, when it isn't engaged just the outer portion with the belt rotates. If it doesn't engage it will not be cool AT ALL not just marginal. At this point you should have someone with a vacuum pump evacuate the system, change the switch, clean the condenser and refill with the correct quantity of R12. Possibly install a new drier as you will be right there installing the switch. You have done all you can do without a vacuum pump and gauges.

 

Read the above posts, they are all right. I had a simialr problem, the cooling wasn't what it once was... I have had a bunch of these cars, as r12 is hard to come by most people switch to r134a, the cooling performance is horrible and it takes its toll on the compressor. I have converted over 14 w123, w124 and 126 cars to propane with fantastic results. Look into it, it has a lower operating pressure, relatively safe and far cheaper, you don't need to replace the drier or replace oils

 

Thanks woodboat and hellspangwl911 for the information. I'll check on the clutch. hellspangel911 where can I find information on converting to propane?

 

By the way, my expeience has been if the clutch is bad it will be covered with dust, like brake dust, and the whole surrounding area... Sometimes tricky to see if your engine bay is filthy. Also a weak clutch will work at idle and not at higher rpms.
As for the propane, you will see I posted various writeups on BMW and Mercedes forums, just search gOogle with my username and propane the hardest part of the procedure is rigging a freeflowing connection for the tank. Go to your local hardware store and buy a BBQ propane hookup tube, check if it has a built in regulator, if it does, yo need to remove any regulating attachment. Have a shop recover the R12, then charge it with propane on the low side to arround 45 psi at 1500 rpms