Easiest test: Transfer switch and recirculating door actuator. I suspect these don't fail very easily. After these the vacuum control switch and then remove the dash and refer to FSM.
Check valves are at this area. They are also easy to test.
Auto temp 2 :(
- Thread starter Giovanni1776
- Start date
Easiest test: Transfer switch and recirculating door actuator. I suspect these don't fail very easily. After these the vacuum control switch and then remove the dash and refer to FSM.
Check valves are at this area. They are also easy to test.
More information:
Better picture of Defrost Actuator installed with shims. Located over the throttle pedal. Other option is to bend the bracket but I thought that would risk ripping off the heater case.
My system was missing the vacuum tank initially. 71-73 Ford Vacuum Can would be very close to the original, but since it was not readily available, I put Dorman 47076 (or similar).
Cold engine lockout valve connectors were leaking. I bypassed entire valve and connectors by 1/8 tube for test purposes. It could be left bypassed depending on preference. This affects directly to Master Switch circuit and minimizing the leak risks here is also beneficial.
ATC Park feature did not work initially because some previous stereo install guy had cut Red-Tracer wire from +12V supply on back of the radio. Park position missing seems not to affect system dramatically.
Better picture of Defrost Actuator installed with shims. Located over the throttle pedal. Other option is to bend the bracket but I thought that would risk ripping off the heater case.
My system was missing the vacuum tank initially. 71-73 Ford Vacuum Can would be very close to the original, but since it was not readily available, I put Dorman 47076 (or similar).
Cold engine lockout valve connectors were leaking. I bypassed entire valve and connectors by 1/8 tube for test purposes. It could be left bypassed depending on preference. This affects directly to Master Switch circuit and minimizing the leak risks here is also beneficial.
ATC Park feature did not work initially because some previous stereo install guy had cut Red-Tracer wire from +12V supply on back of the radio. Park position missing seems not to affect system dramatically.
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commando1
Old Man with a Hat
I’d keep looking for the metal can. The heat in that area is impressive on these 440s.
Great job. Love the thread. Keep it up.
Mr C
Senior Member
To be clear:
AutoTemp II version 1.0 with the under hood servo/ coolant combo assembly ended in 73;
AutoTemp II next gen, 2.0 whatever was 74-78, included separation of the leaky underhood assembly by putting the servo inside the car on the heater box.
For years (literally) I struggled with a situation where all my vacuum issues were under control but I could not get the different modes to work (I only could get defrost air, not air through the dash etc). Turned out to be the amplifier not sending electrical signals to the servo.
Now my system works, but then I had a freon leak (condensor). It's always something...
ImperialLeBaron1969
Member
Thanks, I have never seen that system. I think Autotemp I is quite a nice system. The servo/ coolant combo in the version II seems not like a good combination.
Is it possible to get a new amplifier or to have it rebulit?
Yes you can have the Amp rebuilt or exchange for a reconditioned unit. Contact Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care - Home | Performance Analysis Co.
Has anyone rebuilt Amplifier themselves? There's only few "Through hole" components on PCB and there has to be an electrican here. If single component has been visibly fried, it could be replaced, right? There is not even potting material to be removed. PCB schematic with component information could be handy. I bet a professional could reverse engineer schematic by looking the PCB.
What I learned about 74-78 ATC II
Thread contains almost all necessary information on the system. Sorry for posting messages with duplicate info earlier.
What I learned about 74-78 ATC II
Thread contains almost all necessary information on the system. Sorry for posting messages with duplicate info earlier.
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Mr C
Senior Member
By the way when the system is functioning, it's quite impressive.
Example, One cool morning I had the car (77 T&C) set to "Vent" and the temp swing arm all the way to the left or 65 and noted that there was no fan action...I immediately panicked and thought that the Autotemp II gremlins had struck again, but no. Turns out it was colder outside than 65 that morning, so the system did not push air. Once it warmed up outside to 65 plus, the system came on pushing vent air. Also the fan intensity ramped up with the temperature differential as the day went on.
I think it's very cool to see the system operating to keep the temp where I set it.
Example, One cool morning I had the car (77 T&C) set to "Vent" and the temp swing arm all the way to the left or 65 and noted that there was no fan action...I immediately panicked and thought that the Autotemp II gremlins had struck again, but no. Turns out it was colder outside than 65 that morning, so the system did not push air. Once it warmed up outside to 65 plus, the system came on pushing vent air. Also the fan intensity ramped up with the temperature differential as the day went on.
I think it's very cool to see the system operating to keep the temp where I set it.
Gerald Morris
Senior Member
YES! I would seriously consider replacing the old vacuum controls for one of these systems entirely with modern, electronic thermostatic controls. Mind you, that's a little bit of engineering, but if I were afflicted with a '70s auto AC, that's the path I would take if much of the old system controls were worn out.
Update and conclusion to ATC II repair from my side:
I got the system working. Thank you all for your help.
Further actions in engine compartment.
- Reman RV2 compressor was installed by some of the previous owners. Manufactured around 2004. I installed new steel gaskets to inlet and outlet and checked the ETR-valve. New o-rings to all hose connections. New A/C schrader-valves everywhere.
- New receiver drier (FOUR SEASONS 33340) and cutoff switch (GPD 1711254). C-body drier was not available so truck version is used.
- Evaporator core and expansion valve were stuck. New expansion valve (GPD 3411284). Core and pressure hoses cleaned both directions by compressed air. Found out that 1974-78 Mopar had different style expansion valve seals (DORMAN 488-102) compared to the newer steel gaskets.
- Filled with R-12 substitute refrigerant Isceon 49 (R437A)
The only problem left that I'm aware or is that on LO- and HI-AUTO modes once the system enters heat mode and returns to cooling mode, A/C doors do not open anymore and cold air goes to heat channels. Starts working again if OFF is pressed. I suspect something going on in heat/AC door vacuum lines or mechanism.
I got the system working. Thank you all for your help.
Further actions in engine compartment.
- Reman RV2 compressor was installed by some of the previous owners. Manufactured around 2004. I installed new steel gaskets to inlet and outlet and checked the ETR-valve. New o-rings to all hose connections. New A/C schrader-valves everywhere.
- New receiver drier (FOUR SEASONS 33340) and cutoff switch (GPD 1711254). C-body drier was not available so truck version is used.
- Evaporator core and expansion valve were stuck. New expansion valve (GPD 3411284). Core and pressure hoses cleaned both directions by compressed air. Found out that 1974-78 Mopar had different style expansion valve seals (DORMAN 488-102) compared to the newer steel gaskets.
- Filled with R-12 substitute refrigerant Isceon 49 (R437A)
The only problem left that I'm aware or is that on LO- and HI-AUTO modes once the system enters heat mode and returns to cooling mode, A/C doors do not open anymore and cold air goes to heat channels. Starts working again if OFF is pressed. I suspect something going on in heat/AC door vacuum lines or mechanism.
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Hopefully Giovanni1776 has got help for his original topic.
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