123.133 Climate Control (Is there a True Master?)
07-17-2015, 01:12 PM
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1982 300D
123.133 Climate Control (Is there a True Master?)
1982 300D
I have been troubleshooting this system for a months, i've studied it thoroughly and built it form the ground up.
Here is what right with the system:
- New compressor, lines flushed, condenser and evaporator cleaned and
flushed, new reciever/dryer
- All new heater hoses, core cleaned and flushed
- All vacuum actuators repaired and tested, duct assembly cleaned/rebuilt
(new rubber/seals on all flaps etc...) unit tested out of car,installed and
tested again, new drain, body vent plenum cleaned/drains cleared.
- Vacuum switchover valves tested and verified off car.
- Tested temp sensors off car with heat/cold to verify resistance.
- Mono valve rebuilt and tested off car and again on car
- All wiring tested (resistance and voltage)
- Aux pump removed/bypassed water flow is excellent without it (the cheap
replacement leaked so I sent it back)
- Temp dial overhauled and tested off car (the wiper points wear out)
- All electrical pins/jacks/plugs cleaned and tightened
- All fuses/ grounds are good
- Fan resistor set resistance checked and good
What I have not done:
- Replace CC module, temp reg module, and fan control.
All flaps work properly in operation
Fan speeds cycle through various speeds when in operation.
I did inspect these internally and replaced two questionable transistors
on my spare temp reg module.
Now for the operating parameters/symptoms:
- Defrost works properly
- Off works properly
- T/V (Total Ventilation) works properly (both hot and cold)
Now the problem
- Normal all flaps work properly/cycles center at the right time
compressor runs
monovalve works properly
Fan runs for about a minute then stops
- EC (economy) same as Normal except compressor
Fan runs for about a minute then stops
In other words everything works properly EXCEPT FAN IN NORMAL AND ECONOMY. It runs first try for a short time then stops, after that it will not work at all if I switch to stop, T/V, or DEF then back to Norm or EC after the first try fan does not come on.
Earlier (before I got the Temp dial/sensing circuit right) the fan worked strangely in Norm and E/C It came on and stayed on sometimes and at other times if I "tricked" or "jump started" it by switching to DEF or T/V for a few seconds then back to E/C it would start and stay on.
By the way this problem applies to all positions of the fan switch (High, Low and Auto). High and Low bypass the temp regulator and go straight to the fan controller which would seem to eliminate the temp regulator as the cause and the fact that the fan works in DEF and T/V would seem to eliminate the fan controller.
I hate to easter egg the system, it's not who I am, so I'm not going to start slappin' new parts in to see if it works. New "Genuine Mercedes" parts are too expensive and I don't know whether to trust the outfit that is rebuilding them (if anyone has used them I would appreciate feedback on the quality of their work).
If the electrical schematics were better and included the internals of the circuit boards and chips I could troubleshoot down to a gnat's A$$. I could download the schematics of the chip internals but I would still have to desolder every component to check them and I'm far too lazy to do that.
I suspected the CCU (Climate Control Unit) micro switches as there is a different path through the CCU when Norm and EC and depressed than for DEF and T/V. Maybe it works until the contacts heat up then breaks the circuit, but if it did that it should work again after the contacts cool.
I also suspected the fan control, it always works in high for def (which bypasses) but Norm and EC will try to lower speeds so maybe the Fan Controller or Temp Reg Unit is not able use the middle speeds. The problem with that theory is that I've seen more speeds than just high and low in T/V mode.
Which brings me right back to the CCU switch contact theory The CCU is very difficult to disassemble without damage. I have 2 more apart that i can experiment with to test the theory with.
If nothing else it has been good to write it out as it puts it all straight in my mind. I will post the solution when I find it.
Dan
I have been troubleshooting this system for a months, i've studied it thoroughly and built it form the ground up.
Here is what right with the system:
- New compressor, lines flushed, condenser and evaporator cleaned and
flushed, new reciever/dryer
- All new heater hoses, core cleaned and flushed
- All vacuum actuators repaired and tested, duct assembly cleaned/rebuilt
(new rubber/seals on all flaps etc...) unit tested out of car,installed and
tested again, new drain, body vent plenum cleaned/drains cleared.
- Vacuum switchover valves tested and verified off car.
- Tested temp sensors off car with heat/cold to verify resistance.
- Mono valve rebuilt and tested off car and again on car
- All wiring tested (resistance and voltage)
- Aux pump removed/bypassed water flow is excellent without it (the cheap
replacement leaked so I sent it back)
- Temp dial overhauled and tested off car (the wiper points wear out)
- All electrical pins/jacks/plugs cleaned and tightened
- All fuses/ grounds are good
- Fan resistor set resistance checked and good
What I have not done:
- Replace CC module, temp reg module, and fan control.
All flaps work properly in operation
Fan speeds cycle through various speeds when in operation.
I did inspect these internally and replaced two questionable transistors
on my spare temp reg module.
Now for the operating parameters/symptoms:
- Defrost works properly
- Off works properly
- T/V (Total Ventilation) works properly (both hot and cold)
Now the problem
- Normal all flaps work properly/cycles center at the right time
compressor runs
monovalve works properly
Fan runs for about a minute then stops
- EC (economy) same as Normal except compressor
Fan runs for about a minute then stops
In other words everything works properly EXCEPT FAN IN NORMAL AND ECONOMY. It runs first try for a short time then stops, after that it will not work at all if I switch to stop, T/V, or DEF then back to Norm or EC after the first try fan does not come on.
Earlier (before I got the Temp dial/sensing circuit right) the fan worked strangely in Norm and E/C It came on and stayed on sometimes and at other times if I "tricked" or "jump started" it by switching to DEF or T/V for a few seconds then back to E/C it would start and stay on.
By the way this problem applies to all positions of the fan switch (High, Low and Auto). High and Low bypass the temp regulator and go straight to the fan controller which would seem to eliminate the temp regulator as the cause and the fact that the fan works in DEF and T/V would seem to eliminate the fan controller.
I hate to easter egg the system, it's not who I am, so I'm not going to start slappin' new parts in to see if it works. New "Genuine Mercedes" parts are too expensive and I don't know whether to trust the outfit that is rebuilding them (if anyone has used them I would appreciate feedback on the quality of their work).
If the electrical schematics were better and included the internals of the circuit boards and chips I could troubleshoot down to a gnat's A$$. I could download the schematics of the chip internals but I would still have to desolder every component to check them and I'm far too lazy to do that.
I suspected the CCU (Climate Control Unit) micro switches as there is a different path through the CCU when Norm and EC and depressed than for DEF and T/V. Maybe it works until the contacts heat up then breaks the circuit, but if it did that it should work again after the contacts cool.
I also suspected the fan control, it always works in high for def (which bypasses) but Norm and EC will try to lower speeds so maybe the Fan Controller or Temp Reg Unit is not able use the middle speeds. The problem with that theory is that I've seen more speeds than just high and low in T/V mode.
Which brings me right back to the CCU switch contact theory The CCU is very difficult to disassemble without damage. I have 2 more apart that i can experiment with to test the theory with.
If nothing else it has been good to write it out as it puts it all straight in my mind. I will post the solution when I find it.
Dan
07-17-2015, 03:12 PM
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1982 300D
I forgot - New fan.
I just went back out to the shop after I convinced myself while writing that it could only be the CCU. I had another with no temp dial so I swapped the known good temp dial to the spare and put it in. The system now works 100% for the first time since 1999.
it could only have been weak contacts in the micro switches.
I just went back out to the shop after I convinced myself while writing that it could only be the CCU. I had another with no temp dial so I swapped the known good temp dial to the spare and put it in. The system now works 100% for the first time since 1999.
it could only have been weak contacts in the micro switches.
