87 300D Climate Control woes - PeachParts Mercedes-Benz Forum

jevansx1 · #1 09-20-2018, 02:43 PM

All my vacuum pods are leaking, and my blower will not turn on unless it feels like it. I am going to fix my vacuum pods, but my main problem now is the poltergeist climate control. None of the buttons seem to work, even defrost. If I leave the climate control on, and I simply start driving, occasionally the blower will start running in unison with the recirculation light blinking on the dashboard in some in rhythmic on-off-on-off. Eventually that cycle ends with the blower off. Other times, the blower will just start working on defrost only. Heat and monovalve seem to be working fine. The heat being generated thru the heater core and the car moving is comfortable when the dial is in the white range - not too hot or cold.

I would like to troubleshoot and fix the ACC before it starts getting too cold out, as I need the blower to defrost my windowshield at least. I have done a bit of searching, but I can't seem to find the answers I need for my particular case. At some point I came across a link to a pdf download for FSM troubleshooting guide for the climate control, but the link is now dead. Does anybody have a current link to the manual? Does anybody have some suggestions on what to try next? I know the blower works, and I know the climate control can and does (occasionally) tell the blower to come on. I am leaning toward the ccu as being culprit, but I would like to deduce this with some certainty with testing before I start throwing money and ProGrama for a remanu'd unit.

Some other facts - Aux water pump is dead, terminals test open. It has probably been dead throughout my ownership. It is unplugged currentlyClimate Control was working up until about 2 weeks ago.

vstech · #2 09-20-2018, 03:12 PM

Lift passenger footwell carpet... open plastic cover.

Unplug computer see if things work.

renaissanceman · #3 09-20-2018, 05:20 PM

Quote:

Originally Posted by vstech

Lift passenger footwell carpet... open plastic cover.

Unplug computer see if things work.

Im case this is not clear -- I think he's talking about the "alarm" computer that starts causing issues after the contacts in your driver's side door lock stop working. Mine's been unplugged so long I forgot it even existed!

jevansx1 · #4 09-20-2018, 06:16 PM

Quote:

Originally Posted by renaissanceman

Im case this is not clear -- I think he's talking about the "alarm" computer that starts causing issues after the contacts in your driver's side door lock stop working. Mine's been unplugged so long I forgot it even existed!

Yeah, I was a little unclear. I didn't even know there was computer living under the passenger side matt. I will give that a try and see if things start functioning again and update this tread. Thanks!

jevansx1 · #5 09-21-2018, 02:11 AM

Well... Unplugging the computer that lives under the carpet did nothing whatsoever. But what really did make a difference was replacing the freaking blower fuse. I checked it several times, but looks can be deceiving. When I pulled the old one out, the bridge broke apart in my hand. It must have overheated over time and was hanging by the smallest of threads, allowing the blower to work intermittently and causing erratic behavior. I got real suspicious of the fuse after the blower stopped working completely this evening. Pretty embarrassing... but glad it turned out to be something simple.

renaissanceman · #6 09-21-2018, 11:19 AM

Quote:

Originally Posted by jevansx1

Well... Unplugging the computer that lives under the carpet did nothing whatsoever. But what really did make a difference was replacing the freaking blower fuse. I checked it several times, but looks can be deceiving. When I pulled the old one out, the bridge broke apart in my hand. It must have overheated over time and was hanging by the smallest of threads, allowing the blower to work intermittently and causing erratic behavior. I got real suspicious of the fuse after the blower stopped working completely this evening. Pretty embarrassing... but glad it turned out to be something simple.

Those can be really tricky. Mine blew last winter while it was really damp and foggy. Luckily I was able to get home before the entire windshield fogged since driving fast forced air into the defrost vents.

30 years for the original fuse is not bad...and I have 12 extra fuses laying around since the fuse was something like $0.30 and the shipping was $7...so I should be good to go for another 360 years, haha.