Hey guys,
New to mercedes shop. I am having climate control problems. In Oct of 2001 i replaced the climate control unit. I then had the car sitting from Jan of 2002 to Aug 2004. Now the blower motor works occasionally. when it does work, it either works perfect, goes on and off as many times as you want and blows cool air in the cold setting, or it switches from hot to cool, and will not shut off unless pushing the EC button, and off button repeatedly. Most of the time you switch the system on in the EC setting, no blower motor. If you shut the car off repeatedly, and turn it back on you can usually get it to work. I have replaced the blower motor brushes with the kit from Mercedessouce.com along with the brass fuse upgrade kit. Could it be the temp sensor at the blower motor? I have read in the service manual that this could cause the blower motor to shut off. I know there is also a temp sensor on the evaporator, and also in the cabin. I have replaced the one in the cabin. I'm starting to think it is the climate control unit because of the erratic behavior, ie. not shutting off, blowing hot air even though it is in the cool setting, having air blow out the wrong vents based upon the climate control settings, etc. Even when the blower motor doesn't come on, you can here valves opening and closing in the dash. I've also replaced the monovalve that controls coolant to the heater core. I'm hoping it is not the climate control unit, because the new one has only been used for a few months. Thanks for help in advance.

Mike

Mike, what is the model and year of the car that is causing you trouble?

Sorry Guy's,
It is an 86 300E.

Mike

Since the brushes have been replaced, check the bar fuse near the master cylinder. Don't simply look at it, nudge it gently to see if it is separating at the ends. Sometimes it will stress crack and look like it is making contact, but will do so eratically.

If you are CONVINCED that this fuse is SOLID, then do a search and find the posts that have to do with climate control diagnostic. Use an LED and a jumper wire to see if there are any diagnostic codes stored by tapping at the diagnostic connector near the battery.

Good luck,

Hey Larry,
Thanks for the info. I looked for the bar fuse, and could not find it. I saw some connectors, but no fuses. Could you describe it and location a bit more or post a pic? As far as LED, jumper, and checking for codes goes, I'm not familiar with this. Could you describe this procedure in more detail? Thanks for all the help.

Mike

Describing the procedure for drawing the CC system diagnostics is a very lengthy and detailed post. To save me a very long time in writing it, could you please do a search on Climate Control Diagnostics or some such to find the threads. There are some threads that go into this in great detail.

The fuse box is a rectangular, black plastic box that is in the area near the master cylinder It is about a 1 1/2 inches long and a half inch wide with a cover that snaps loose to unhinge and reveal the fuse. This is a strip fuse that is about an inch or more long and a 1/4 inch wide. There is a screw on each end of it. At the screw is where it will stress crack sometimes and give intermittent contact.

I am trying to get ready to go out of town on a business trip so I don't have time to take a picture. If you were to search on blower motor fuse, you will probably come up with a thread or two where a picture has been posted.

Good luck,

Hey Larry,
Thanks for the info, I think I now know where the fuse is. I will also search for the diagnostic. No need to write something that is already out there. Thanks for the help. I will keep updating the progress.

Mike

Hey Guys,
I really want to thank the forum for help. Between the help of Larry, and reading some posts I figured out the blower motor problem. It turned out to be a pretty easy fix. The ignition tumbler was the culprit. After all that work all I really had to do was jiggle the ignition lock. I'm not sure I'm out of the woods with everything yet, The system needs a recharge, so I'll need to do that before the AC will work, but at least the blower motor now works. I did have to unhook the aux water pump because it was going from hot to cold, but after that was unhooked it blew cool air. I'm still not sure if the aux pump blew the cc unit, will have to test it to see if it works properly. Thanks for the help guys,

Mike