e36 automatic air conditioning controls

97' 328i sedan 50k miles

Recently the automatic air conditioning control system and blower fan
have been giving me problems. For example, this morning when I turned
the car on there was no power for the control system, I couldn't turn
the heat on, the air-conditioning, defroster, change the temperature,
adjust the fan speed; none of the buttons worked the fan wouldn't turn
on, there was no air supply and the screen to the control system was
blacked out, the whole system had no power. Five minutes later as I
was driving to work the automatic air conditioning control system
suddenly had power and the blower started pushing air through the
vents. I ruled out a blown fuse and assumed it was some type of
electrical short. The weird thing is after the whole system had power
the automatic air conditioning control system would short out or lock
out, and this time the fan would still be supplying air and the
control system would lock out into some safe mode. The control system
still had power but the led lights and the screen lights were dimmed
and locked into the original temperature settings befor the short.
I've driven long periods where the whole system worked fine, where the
whole system had no power and also when the whole system was locked
into the original temperature settings. ?? I guess my question is,
first if any one understands my problem, second, if any one knows what
my problem is or has any input on the matter, third, how could I gain
access to the back of the automatic air conditioning control panel to
see if there are any wires shorting out or crossing, fourth, if no one
knows what the specific problem is what should I do to have it
checked.

Thanks for taking the time to read my problem,

On Thu, 14 Oct 2004 10:05:30 -0700, Q boy wrote:

> 97' 328i sedan 50k miles
>
> Recently the automatic air conditioning control system and blower fan
> have been giving me problems...

Coincidentally, I just fixed this very problem on my car ('99 328is, 120k)
last night. The problem is the climate control computer module in the
dash, and I found instructions on the web (search Google for 'E36 climate
control fix') to fix the problem. It does involve some soldering, and
replacing a failed capacitor (less than $1) on the circuit board.

All in all, it's a pretty easy and very cheap fix, even for someone that
has never done electronic work before, and if you have to buy all the
tools. If you don't want to tackle it yourself, I've also seen people on
eBay selling the service of replacing the capacitor for around $40-50. If
you don't repair your existing module, the only alternative is a new
climate control module costing hundreds of dollars, even from the cheapest
online sources...

Good luck!

I agree with Hrrm on the capacitor problem. I did this fix for a friend
earlier this year. One of the excellent articles you will find on the
web cast some doubt about whether the capacitor should be 47 uF (micro
farad) or 0.47 uF. The correct value is 0.47 uF. Furthermore, ceramic
capacitors of that value often have horrible temperature
characteristics. (X7R dielectric is fine with +/- 15% over -55°C to
+125°C, but Z5U +22%/-56% over +10°C to +85°C and Y5V with +22%/-82%
over -30°C to +85°C will not work in a car environment.

If you can get a ceramic cap with the X7R characteristics, you can use
it. Better yet is a polyester film capacitor, like part number P4671-ND
from http://www.digikey.com or part number 75-MKT1826447064 from
http://www.mouser.com. Tantalums can be used, but you have to observe
right polarity. That means figuring out what IS the right polarity;
Since the original cap is not polarized, the circuit board has no
markings for polarity.

Hrrm wrote:
>
> On Thu, 14 Oct 2004 10:05:30 -0700, Q boy wrote:
>
> > 97' 328i sedan 50k miles
> >
> > Recently the automatic air conditioning control system and blower fan
> > have been giving me problems...
>
> Coincidentally, I just fixed this very problem on my car ('99 328is, 120k)
> last night. The problem is the climate control computer module in the
> dash, and I found instructions on the web (search Google for 'E36 climate
> control fix') to fix the problem. It does involve some soldering, and
> replacing a failed capacitor (less than $1) on the circuit board.
>
> All in all, it's a pretty easy and very cheap fix, even for someone that
> has never done electronic work before, and if you have to buy all the
> tools. If you don't want to tackle it yourself, I've also seen people on
> eBay selling the service of replacing the capacitor for around $40-50. If
> you don't repair your existing module, the only alternative is a new
> climate control module costing hundreds of dollars, even from the cheapest
> online sources...
>
> Good luck!