91 350 sdl have had problem with center vent flaps closing on AC and diverting air to defrost flaps. At times I can adjust by turning temp wheel to the red area, center vents will then open. Any ideas of problem?
Next probelm compressor froze, broke part of serpitine belt, broke wires to compressor. Replaced compressor, no power to compressor, jumped reply, compressor works looks like needs new reply. Now the center vents will not open at all, help!

The power supply to the A/C Compressor Clutch is fed from Fuse #5, so check that first. That fuse also supplies power to the ACC (Automatic Climate Control) and that in turn controls the vents. It has been reported here by a number of people that when the Compressor seizes (which overloads the Clutch) this can damage the ACC.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

Swapped Climate Control unit have the same issue with flaps.Any suggestions?
Would the relay have any effect on the ACC?

There is a large Black relay mounted on the firewall toward the centre on the drivers side. This is the Klima Relay and it controls the power to the A/C Compressor. It takes its signals from the ACC. If the Klima Relay is damaged it may be messing up the ACC unit, I'm not sure. Is the fuse OK?

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

The fuse is OK, the relay had a bad diode, resodered got power to compressor but will not turn off even with the ACC turned off. Looking to replace relay. Had flap problem previous.

If ACC is really OK then Flap problems may have more to do with the vacuum actuators.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

This is strangely ironic - I read this forum last night, then TODAY had the same problem with the center flaps and A/C!! The side flaps work fine and the air is still pretty cold, but all the cold air is diverted to the defroster vents on the dash! The only thing that immediately preceded this problem was this - 2 small pieces of black foam rubber insulation blew out of the vents... Could this have something to do with it??? After a while the vents open and the cool air is split between the dash and defrosters, but it doesn't seem to close the defroster vents completely. Any advice would be GREATLY appreciated - I am a saxophonist living in Las Vegas and the projected high for tomorrow is 111F!!! I need my A/C!!!

For all of you with flap problems, the usual culprit is that one, or more than one, of the vacuum pods that actuate the flaps have a leak. When this happens, the pods don't function at all or function marginally. The default position is always defrost, because the defrost pod requires vacuum to close.

You fellows need to do a proper check of the pods by getting to the set of vacuum switches. The six switches sit directly to the right of the CCU and and extend downward toward the radio. To access them, you need to remove the passenger kick panel and the carpeting along the transmission tunnel on the right side. Then, you'll see them immediately. For greater access, remove the two screws that hold the group to the body.

Now, you can properly test each circuit with a Mityvac. The horizontal leg of the vacuum switch goes to the vacuum pod. Disconnect it from the switch and pump it up. The circuits that don't hold vacuum require that the pod be rebuilt and/or replaced.

You can get at most pods via removal of the glove box liner. A couple of them are accessed from behind the CCU. One of them is accessed via the driver's kick panel.

If you don't want to chase down the defective pod, you can disconnect and plug that circuit.

You can also route full vacuum to the dash vents, thereby bypassing the control of dash vents by the CCU. You then get air from the dash under all conditions, and can modulate it via the sliders. It's a great modification which I recently did on the SD. However, the pod on the dash vents needs to be functional for this to work.

If you have defective single pods, you can rebuild them cheaply. If you have defective dual pods, you'll have to bite the bullet and purchase new. The rebuild kit doesn't provide the proper travel when you get finished with the install.

It'll take you a bit of time to sort out this system, so don't dive into it under pressure of time. It took the better part of one week for the SD..........disassemble, diagnose, order parts, install, reassemble, return to service.

Air not coming out of center vent in my 90 sdl was a vac hose had come loose.
When my ovp relay retired the a/c would blow warm.

__________________
82 300D....went to MB heaven
90 350 SDL....excercising con rods

If the compressor locked up, you will need to replace the reciever/dryer, expansion valve, and do a complete flush to removed any metal shavings that are created just before the compressor locks up.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D