Climate control-constant heat issue
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Climate control-constant heat issue
I'm starting to work on several issues my old '82 SEC has. Frist I'm looking into the climate control system. I have constant heat unless I roll the dial all the way up to get the AC to come on, and then it blows cold. I've checked the monovalve inside and all looks good; rubber is in fine shape with no cracks or deterioration, and the solenoid works the plunger. I did notice that the solenoid is active (plunger extended) no matter what setting the system is on. Is this correct? Are there any other rubber components within the monovalve body itself that I couldn't see?
My next stop in this diagnosis is resoldering/cleaning the control board. The blower works on high/low speeds, but not all the time in all switch settings. This seems like a needed thing to do on a 20+ year old car. What else can I look for if this doesn't take care of the problem?
Cliff
My next stop in this diagnosis is resoldering/cleaning the control board. The blower works on high/low speeds, but not all the time in all switch settings. This seems like a needed thing to do on a 20+ year old car. What else can I look for if this doesn't take care of the problem?
Cliff
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From: Nashville
300SEL
Originally Posted by homeline
I have constant heat unless I roll the dial all the way up to get the AC to come on, and then it blows cold.
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Yep Black Wagon, that's pretty much it. Just this evening I took dash apart and removed the control box. It's got a date code of 2001 and a "www" address, so it's obviously been replaced. Thats not to say it could still have a problem, but I kind of doubt it. Since I can see behind dash now, I'll ivestigate some of the vacuum valves to see if they are working correctly. Maybe a temp sensor somewhere is faulty?
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From: Nashville
300SEL
Originally Posted by homeline
Yep Black Wagon, that's pretty much it. Just this evening I took dash apart and removed the control box. It's got a date code of 2001 and a "www" address, so it's obviously been replaced. Thats not to say it could still have a problem, but I kind of doubt it. Since I can see behind dash now, I'll ivestigate some of the vacuum valves to see if they are working correctly. Maybe a temp sensor somewhere is faulty?
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Originally Posted by schwarzwagen
could be the temp sensor, it's mounted on your early 126 in the center of the dash. is the control unit a reman from ProgRama Inc ? i've had several parts from them, nothing has given me any fuss yet. since the obvious place, the monovalve, is not the problem and the control unit is newish. i would check the temp sensor now. the MIN detent overrides any readings coming from the temp sensor and basically is just the MAX COOL function found on other cars.
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From: Nashville
300SEL
Originally Posted by homeline
I do believe Programa is the name. And yes, from what I've learned (from Mercedeshop) the I/S sensor is over ridden by the MIN detent. It's been suggested to look at the O/S temp sensor. Now I just have to locate that O/S sensor.
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From: Kentucky
500E's
If the problem is with the heater blowing a constant heat on the INSIDE of the car -- always hot -- why would the outside temp sensor be an issue here?
I am having the same problems. They replaced the blower motor (not the problem at $400) so I am now looking at the two inside components. Either the Climate control unit or the Inside Temp Sensor. Is there anything else that is in that system that would make the Auto setting just not work and the only way to keep the car comfortable is to turn the system on and off to maintain a normal climate?
Also, Homeline, is that you Cliff?
I am having the same problems. They replaced the blower motor (not the problem at $400) so I am now looking at the two inside components. Either the Climate control unit or the Inside Temp Sensor. Is there anything else that is in that system that would make the Auto setting just not work and the only way to keep the car comfortable is to turn the system on and off to maintain a normal climate?
Also, Homeline, is that you Cliff?
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[QUOTE=I am having the same problems. They replaced the blower motor (not the problem at $400) so I am now looking at the two inside components. Either the Climate control unit or the Inside Temp Sensor. Is there anything else that is in that system that would make the Auto setting just not work and the only way to keep the car comfortable is to turn the system on and off to maintain a normal climate?
Also, Homeline, is that you Cliff?[/QUOTE]
Yep, this is Cliff. Who's this? I can't hide anywhere!
I'm controlling the temp the same way; turning on and off. I'm going to try and check all components of the control system to get this straightened out. If I can't find culpri I may take to a dealer and have them diagnose the problem.
Right now this is on hold; I've got a heck of a leak from the transmission pan gasket. I know the mechanic over torqued the bolts. When I loosened them up, a substantial reduction fluid loss was noticed immediatley. But I still have a constant drip in a certan spot. I think the pan may bent. I see some kind of goop that was squirted in there at that spot. Probably will wind up dropping it and examining. It's ture what they say, "If you want something done right, you better do it yourself"
Always something!
Cliff
Also, Homeline, is that you Cliff?[/QUOTE]
Yep, this is Cliff. Who's this? I can't hide anywhere!
I'm controlling the temp the same way; turning on and off. I'm going to try and check all components of the control system to get this straightened out. If I can't find culpri I may take to a dealer and have them diagnose the problem.
Right now this is on hold; I've got a heck of a leak from the transmission pan gasket. I know the mechanic over torqued the bolts. When I loosened them up, a substantial reduction fluid loss was noticed immediatley. But I still have a constant drip in a certan spot. I think the pan may bent. I see some kind of goop that was squirted in there at that spot. Probably will wind up dropping it and examining. It's ture what they say, "If you want something done right, you better do it yourself"
Always something!
Cliff
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From: Stouffville, ON Canada
2004 S500; 1991 300SL
If as you say, the monovalve is activated all the time and you still have too much heat, then the monovalve is most likely the problem.
Do the following tests with a cold engine to start:
- disconnect the electrical connector to the monovalve and connect a volt meter, an analog one is preferable.
- start the engine and push the climate control 0 (off) button and you should have constant 12 volts and no heat
- select a fairly low temparature and observe the meter. It should go to zero and then should alternate between 12 volts and zero volts once the set temperature has been reached.
- if this is the observed behaviour, then all the sensors and controls are normal and the monovalve is leaking despite the solenoid working. get the repair kit and replace.
I just repaired my system 2 days ago. Same symptoms as yours. A rivet like stopper had come off the monovalve plunger end and travelled through the engine water passages to the thermostat where it jammed the thermostat open.
Do the following tests with a cold engine to start:
- disconnect the electrical connector to the monovalve and connect a volt meter, an analog one is preferable.
- start the engine and push the climate control 0 (off) button and you should have constant 12 volts and no heat
- select a fairly low temparature and observe the meter. It should go to zero and then should alternate between 12 volts and zero volts once the set temperature has been reached.
- if this is the observed behaviour, then all the sensors and controls are normal and the monovalve is leaking despite the solenoid working. get the repair kit and replace.
I just repaired my system 2 days ago. Same symptoms as yours. A rivet like stopper had come off the monovalve plunger end and travelled through the engine water passages to the thermostat where it jammed the thermostat open.
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Originally Posted by elbe
I just repaired my system 2 days ago. Same symptoms as yours. A rivet like stopper had come off the monovalve plunger end and travelled through the engine water passages to the thermostat where it jammed the thermostat open.
Cliff
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From: Kentucky
500E's
Cliff,
It is Mark that bought your interior panels on ebay.
I just checked the dealer price for monovalve is $99 and temp sensor is like $79. I think we can do better. I have the two climate control units coming in this week and will see if these send better signals to the blower. Not sure if it is the problem but I just have a hunch. Hopefully I will know what is going on by the weekend.
I played with the blower that the mechanic took out of the car and it really was in bad shape. I guess 200,000 miles of blowing will do that (insert joke here).
And elbe, thanks for the instrument reading tip. That will be first on the agenda this weekend. Hopefully it will be above freezing.
It is Mark that bought your interior panels on ebay.
I just checked the dealer price for monovalve is $99 and temp sensor is like $79. I think we can do better. I have the two climate control units coming in this week and will see if these send better signals to the blower. Not sure if it is the problem but I just have a hunch. Hopefully I will know what is going on by the weekend.
I played with the blower that the mechanic took out of the car and it really was in bad shape. I guess 200,000 miles of blowing will do that (insert joke here).
And elbe, thanks for the instrument reading tip. That will be first on the agenda this weekend. Hopefully it will be above freezing.
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Posts: 169
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From: Kentucky
500E's
Elbe
Thanks for the headsup on the monovalve price, i just got quoted 99 from stealer before MBCA discount. Yikes
Also, I got a Climate control unit in the mail today so this weekend should be testing time. I will update, with pix when I am either done or in way over my head. Either way, it should be fun.
Thanks for the headsup on the monovalve price, i just got quoted 99 from stealer before MBCA discount. Yikes
Also, I got a Climate control unit in the mail today so this weekend should be testing time. I will update, with pix when I am either done or in way over my head. Either way, it should be fun.
