[W124] [Mercedes] I'm sticking with my current MB for a while, so a new and challenging question

[Steve Nervig]

On Dec 20, 2007, at 12:40 PM, Alec Cordova wrote:


> I didn't get that 1980 300SD on eBay, but I did get something

> interesting out of my 89 300CE the other day.

>

> The climate control air recirculation button, up on the dash with the

> rear defrost and rear light buttons, started blinking at a consistent

> rate, somewhere around half as fast as my turn signals blink. What the

> heck does this mean?

>

> Car is an 89 300CE (US model) with 231K miles. Climate control only

> partially works. I get decent temperature control, but the fan doesn't

> work, and the system has virtually no control of the vents. Ram air

> comes through the side vents, the defrost vents, and the floor vents,

> although I do seem to get a little more from the floor vents when I

> select bilevel A/C instead of just Econ mode.

>

> It got warm again here in central Texas just a week or two ago (low

> 80s), and I heard a cyclical snapping sound from behind the dash

> (slightly toward the passenger side?) that could have been the ACC

> trying to change the air routing, but with no success. It was at least

> a week after that event, which has not recurred, that I got the

> flashing recirc button, and it happened while driving home in the

> evening, so the system was in heating mode. While flashing, the air

> coming from the side and defrost vents _almost_ felt a little hotter

> than usual, and it may have been coming out of the defrost vents more

> than usual, although I rarely feel up there to see how much air comes

> through.

>

> Selecting the Off switch on ACC did not stop the flashing. It was gone

> the next morning when I started the car, and it has not yet returned.

>

> Anybody know the answer, other than just guessing that my climate

> control pushbutton unit had a minor stroke?

>

> Thanks,

> Alec Cordova

> Taylor, Texas

> 89 300CE, 231K


Alex, I found this thread pertaining to the W126, but the systems are  
similar. Not real sure if it answers the question:
<http://www.benzworld.org/forums/w126-s-se-sec-sel-sd-sdl-class/1310594-why-my-air-recirculation-switch-blinking.html 
 >

This link seems a bit more definite - suggest low voltage (alternator  
brushes?), but also suggesting that you have connected a diagnostic  
tool (hmmm):
<http://mercedesshop.com/shopforum/showthread.php?p=1657902>

I have read about a similar situation with seat heater switches -  
blinking LED means not enough voltage.

How are your brushes?

Regards,
Steve
1992 300CE Sportline