Climate Control

[hifeverz]

RE: 300SL 1990

I would like to remove the climate control unit with the least possible damage to the wood trim. Can it be pulled from the front?? . . . or are fasteners located in rear?? From some of you experts out there some Procedures and hints please.

Is there a means to check if the unit is operating properly??? bench test?? an independent service company that does this for low $$.??

I've read many of the threads on erratic A/C operation. Mine is similar to those I read about. My A/C blows cold for as long as an hour(2 hours when I drove from L.A. to San Francisco) then only HOT air gradually takes over. I noticed that the clutch to the compressor is engaged and still pumping . . . something. I was intending to change out the climate control unit (as I have an extra) and if unsuccessful, will replace the expansion valve.
The expansion valve is accessed on the passenger floor area??

I'll replace the interior temp sensor if the above doesn't do it. And this all fails I'll take it to a shop and pay.

Thanks,
HZ

[bobterry99]

The controller easily pulls straight out once you push down on two catches which engage its bottom side. But you have to remove the radio to access the catches. Diagnostics for the controller are explained here: Climate control diagnostics on '90 - '95 R129 SLs

The expansion valve is in the engine compartment on the firewall close to the brake booster. You will need to remove many of the components in front of the windshield to access it.

[hifeverz]

bobterry99

Thanks for the info. on removal of the unit.

The Diagnostics codes are helpful and I already have those from a diagnostic manual I acquired copies from. My climate control did NOT display any relative code to the listing. Am I to assume that it is defective?? Do u know of any test procedures that I could go through without getting this one rebuilt. I learned of an individual that would rebuild it for $300. I would prefer to try to change out this one with another (not sure if it is good) one I have before sending either one off.

How many hours do u estimate for the R&R of that expansion valve??

Thanks,
Hz

[bobterry99]

Referring back to the first post, there is no point in arbitrarily replacing the interior temperature sensor. You can so easily check if it's working through diagnostics.

When your compressor is running and you are getting warm air through the vents, the only way I see the controller possibly being a problem is if it is opening the monovalve and flowing hot coolant to the heater. You can run diagnostics and verify this is not happening and that the heater is at roughly ambient temperature.

Your problem is more likely low refrigerant or a bad expansion valve. If you see bubbles in the site glass of the receiver, then your A/C needs a charge and may have a leak. And if you measure low and high pressures with a set of gauges you can diagnose both low pressure and a faulty expansion valve.

It takes about two hours to remove and replace the expansion valve.

[BobH]

HZ,
I have a 1990 300 SL and had those identical symptoms.I had the expansion valve replaced in June, 2002. I haven't had a problem since then.

Bob