I just purchased a 1985 300d. They have the blower motor hot wired straight from the battery ( I since have put an inline fuse in that line)with a new switch which causes it to run at max all the time. My problem is I have no climate controls or blower controls. I have power to one of the pins that connects to the right side on the controller. If I manually energize the vacuum solenoids my flaps will move but I am not getting anything to work through the controller to them or the fan. I did try another controller and still same outcome...nothing! What would be the first thing for me to start trouble shooting? The fuse at fuse box has power on both sides. I have no idea if the ac works, if that would cause any effect. I know there are sensors in the ducts and under the driver seat but I'm not sure if these would cause nothing to happen. About the only thing I have not done is pull out the blower resistor box behind the glove box. I am new to this automatic climate and really would just like it to work manually if possible and not have to worry about all these sensors.
Remove the passenger kick panel and look up toward the vent. There will be a silver looking box with a red fuse on top of it, this is the overvoltage protection relay. Remove the silver box from the prongs it sits on by pulling straight up and rocking side to side ever so slightly and inspect the fuse.
I do know that the A/C not working has nothing to do with other climate control functions. I did however have a problem with the auto blower switch on the control unit, the white button. It seemed that the control unit would reach the correct temp but when it signaled the blower to reduce speed, there would sometimes be a shit ton of clicking going on behind the control unit. The fan speed would never drop back down on its own so i always had to manually push the low setting.
I pulled the CCU and opened it after I realized the warranty was up on the rebuilt unit. The first thing i saw was a burnt strip metal. I soldered it after cleaning it and now, the fan speed works as it should on the auto setting. I'd say open the box up and see if anything looks burnt, its a common problem.
I opened my ccu up and I did not see anything wrong. It even had sealing tape on it so I imagine it was rebuilt at some point. I have power 12vt at pin 4 on the right side on the unit, some pins have less voltage, should there be more power supply to run the controls and blower? Anyone know what wires should have power with the key on? I have no control of the vents or blower. if I energize the vacuum solenoids the flaps all work so I know no power is making it through the ccu. checked all fuses and strip fuses and they are good(only strip fuse I found was under the steering column). Would the Temp control Module behind the glove box have anything to do this this problem? I have checked
I had that problem and and while fixing a separate issue concerning vacuum lines it fixed itself. In fact when I decided to block out the door system, I replaced all the connections under the hood from the source at the T from the main line from the pump. many things just improved after that. when my shopping list for AZ autopart or whatever the name is Ill order the main door lock valve in the drivers door, shippings to high for a $30 part, gotta bulk up before ordering lol. good luck!
1977 300 D 200K mi
1980 450SL 110K mi
Thanks but it does not seem vacuum is my issue as nothing electrical works on my ccu and blower fan. If I jump power to the solenoids all my flaps work so thats telling me vacuum is there. Does anyone know what pins supply power to the ccu? I only have a full 12 volts at pin 4 on the right side. Some others have less than 12 volts. My fuse in fuse box looks like it melted at some point but I do have 12 volts on both sides on the copper. I have read that at some point the blower fuse was moved to a strip fuse somewhere. Anyone know where that would be located? I found a strip fuse under the steering column but I think thats for the glow plugs.
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