AC question on my 86 300SDL..... - Page 2 - PeachParts Mercedes-Benz Forum

tangofox007 · #16 08-17-2009, 03:09 PM

Quote:

Originally Posted by daw_two

The monovalve "rebuild" kit is easy to replace. I did it. If you are standing on the passenger side of your car next to the battery, the monovalve is toward the driver's side looking over the battery. If memory serves me correctly, you don't have to remove the entire valve (it's a boxy kind of looking thing with 2 rubber coolent hoses and an electrical connection). You can unplug the electrical connection and take the 2 screws (do NOT drop) out of the top. The thing "pops" open (is there a spring in there? I don't remember). Inspect the diaphram on the top of the brass looking shaft --- It probably has a tear in it. Coda's did.

At this point, there is nothing that suggests that a monovalve repair kit is needed. A torn monovalve diaphragm does not typically cause the symptoms presented.

Hip001 · #17 08-17-2009, 03:27 PM

Quote:

Originally Posted by tangofox007

At this point, there is nothing that suggests that a monovalve repair kit is needed. A torn monovalve diaphragm does not typically cause the symptoms presented.

I'm not sure about the dash lights or the fuses. I will check them when I get home from work.

Daw_two, Just waiting on a slip to bust someones b@lls aren't ya! LOL! Good catch my friend!(I did the edit correction)

I will double check the fuses and the 10A on the OVP. and for grins double check the monovalve location/connections. If I understand correctly it is sounding more like electrical issues now.

Brandlj, There are no indicators on the dash showing anything different than normal.

Can someone tell me what "KLIMA" is?

brandlj · #18 08-17-2009, 03:55 PM

KLIMA is the relay that controls your A/C compressor. On our 300sdl's we have certain things that go through the KLIMA relay that lets the compressor know if it should be on or off.
1. Belt slippage on the A/C pulley. There is a RPM sensor that will shut off the compressor if the belt slips or if the belt falls off etc...
2. Wide open throttle microswitch. When the throttle is wide open, foot to the floor it actually touches a microswitch in the engine compartment that shuts off the compressor.
3. High temp switch. Once the engine reaches 105 degrees a temp sensor in the housing on the engine by the upper coolant hose sends a signal to the KLIMA to shut off the compressor and turn on the high speed electric fan in front of the condensor.
4. Pressure switch on the drier. If the pressure in the A/C system is too high or too low it sends a signal to the KLIMA to turn the compressor off or not to turn it on.

If there are any more that I have not touched on, please add them.

daw_two · #19 08-17-2009, 04:06 PM

Quote:

Originally Posted by tangofox007

At this point, there is nothing that suggests that a monovalve repair kit is needed. A torn monovalve diaphragm does not typically cause the symptoms presented.

I concur --- I was merely suggesting to him how easy it is to replace the monovalve IF it were the issue.

daw_two · #20 08-17-2009, 04:12 PM

Quote:

Originally Posted by brandlj

KLIMA is the relay that controls your A/C compressor. On our 300sdl's we have certain things that go through the KLIMA relay that lets the compressor know if it should be on or off.
1. Belt slippage on the A/C pulley. There is a RPM sensor that will shut off the compressor if the belt slips or if the belt falls off etc...
2. Wide open throttle microswitch. When the throttle is wide open, foot to the floor it actually touches a microswitch in the engine compartment that shuts off the compressor.
3. High temp switch. Once the engine reaches 105 degrees a temp sensor in the housing on the engine by the upper coolant hose sends a signal to the KLIMA to shut off the compressor and turn on the high speed electric fan in front of the condensor.
4. Pressure switch on the drier. If the pressure in the A/C system is too high or too low it sends a signal to the KLIMA to turn the compressor off or not to turn it on.

If there are any more that I have not touched on, please add them.

KLIMA probably stands for the first letters of a phrase in German that when translated means something like one of the following:

"The mother thing that must work for the AC to work"
"The queen mother component of the AC circuit"
"The ('B' word) --- why did those Engineers design this thing?"

Well, you get the idea. The engine lives by and the AC dies by the control under the KLIMA.

I just thought of something for Hip001 to check. I bet when he is not experiencing #1 in brandlj's post, he is experiencing #2.

No wonder his AC compressor isn't on.

Hip001 · #21 08-18-2009, 09:28 PM

ok, go figure this dam thing started working somewhat on the way to Pierre's shop. but something was still not right due to some of the air flowing out the defroster. Pierre is getting me some kind of actuator something to direct the flow better when we test drove it we smelled smoke

electrical smell. looked in the fuse box and the blower fuse was melting but not blown

, he said the blower resister or something like that was prob the issue.

brandlj · #22 08-18-2009, 10:41 PM

I have a mid 86 model that has the blower fuse mounted externally from the fuse box in a separate 30A fuse holder. This mod was performed by the factory on mid 86 and on 126's to prevent the melting of the fuse in the fusebox on your car. The upgrade is still available and very reasonably priced. I updated my blower fuse on my 85 380se this summer. Apparently as our blower motors age they draw more current than the original 25A fuse and fuse holder in the fuse box can handle.
I still think you have a CCU problem, but that is just my opinion sitting at desk and not even looking at your car. I am sure Pierre will get you fixed.

Good Luck

Hip001 · #23 08-19-2009, 08:04 AM

Brandj, Yes Pierre did mention the external fuse mod. I will look into getting this done too. I feel like you about this being a multi issue problem and not ruling out the CCU yet.
On my 300D he had to replace the vacuum actuators(I think it's called) behind the controller for proper vent flow.

myself I'm not convinced that the monovalve is working 100% due to the temp coming out of the vents.

brandlj · #24 08-19-2009, 08:31 AM

I agree about the monovalve issue. Early last year in the winter I had an issue with my car's climate control system. It was winter and I had no heat at all. It turned out to be a rip in the monovalve's diaphragm. It was a very,very easy 15 minute fix with a new monvalve insert kit.
The strange thing was that at the same time that the monovalve diaphragm ripped from old age, my car would start to only blow air out of the defroster vents. I found out that by turning the car off and turning it back on, my CCU would reset and all would work well for about 5 minutes and then back to the defrost mode. After doing research on this I learned that the CCU units in the 86 on 126's have a default mode that when the CCU fails, it automatically reverts to defrost only. I also learned that a failing aux water pump ( which sits attached to the monovalve) can draw more current than the CCU can handle. A lot of people have put a 1 Amp inline fuse in the power wire to the aux water pump to keep it from drawing too much current and burning the CCU. We are somewhat lucky in our 86 and on models that when this happens in our cars, the built in circuit breaker in the CCU will trip and then our cars will have defrost only.
I then looked at my aux water pump and it was toasted. I replaced it but still was having difficulties with the CCU to work correctly. I hoard parts that I have found in wrecking yards and had another CCU from a different car, and installed it and all is well now.
There are companies that rebuild these units if yours has failed. I believe Programa has a website that actually has a troubleshooting section that you could use to check your entire CCU system. I did this with a simple ohmmeter by disconnecting the two large wire harnesses on each side of the CCU and then using the wiring harness of the car to check all of the assorted sensors that send signals to the CCU. It really was not as difficult as it sounds and the website has the instructions on which terminals you use to test the different sensors.
By the way, just for your information, on the PRE 1986 cars, when the aux water pump seizes and draws too much current, you will actually burn up the circuit board in the CCU. Search this site and there are many, many posts on this occurring.
Good Luck and keep us posted on your progress.

Hip001 · #25 08-19-2009, 10:20 AM

Brandj,
Thank you for your input! the car does not switch completely to the defrost but is more like 70%vent/30%defrost right now.

I'm not familiar with the Aux water pump? where/what is it? Where do you put the external fuse?

Soon as I get my two windows(Fr & Lr) working, I'm gonna have the windows tinted like my 300D. this will help too in this Florida Sun.