contact148

Ok my 2003 c240 4matic wagon the ac works fine nice and cold no problems with it

I leave it in auto all the time

today when i left work it was off so i pressed it it ran for 10 secs and shut off again it did this 3 times then i just turned the fan on manually ac worked fine

tried auto again turned off waited 5 mins all was well

it did this 2x about a month ago but thought nothing of it

works fine in manual but auto is hit or miss any ideas??

control unit is the analog one

LILBENZ230

Mine has been doing this for 2 years now, I just leave the fan manually on 1 and then hit "AUTO" and it works fine. It's a problem with the control module.

jcnash

The battery being low on power also causes this.

When this happened on my coupe a year or so ago, I switched off all environemntal control (fan/ac), rolled the windows down and went for a nice long drive on the highway to charge the battery up.

Worked like a charm.

mleskovar

+1 I've noticed it happens more when the battery is low as well.

LILBENZ230

My battery has been low on power for 2 years? Nah.. mine definitely has a different issue common on the facelift cars which have different units than you guys.

Viper98912

Auto in my car is blow full speed regardless of how cold it is in the car, so I always run it in manual. But in manual, there are rare times when the A/C randomly shuts off, blowing zero air. It'll kick on a minute or two later. I have no clue what it is, I wonder sometimes if it's low on R134 or something. I live with it I guess, as long as it comes back on I feel it's nothing major.

contact148

battery is 1 year old MB battery

worked fine yesterday all day.....

ericgoh

I think it's a dirty/old potentiometer (or stepper, not sure which one it is).

When left on 0 and Auto, I think it makes intermittent contact and turns the system off. Just leave it on a setting other than 0 and Auto and it should go away. We just leave it on 3 and Auto all the time and the problem doesn't happen.

Next time I have the center panel apart, I'll take that entire unit apart and figure it out. The pot probably just needs a little Deoxit spray.

jcnash

I didnt say it might be a "bad" battery causing it. I said a battery that is low in power/charge might cause this same issue.

Also if it worked fine yesterday, maybe the battery had time to charge up. Try charging it by driving long range with as many power consumers as possible (like AC etc) turned off. See if that fixes the issue

d1no

Mine does this too, 05 c230 kompressor 6spd it drives me crazy. The ac shuts off and after a when I open the window it kicks back on. I don't want to take it to the dealer because they charge too much. Like over 300 to recharge the a/c.. wtf

LILBENZ230

Turn the fan speed to something manually, then use the Auto feature all you want. It'll work fine. Mine has for 2 years now.

vdubpower

mine did that, when i lived in florida, cant recall the issue, goto dealer, tehy will fix it

Shadow5501

Problem sounds like the common issue with the blower fan motor and blower regulator. The blower regulator is the electronics which drive the fan and control its speed. It's located with the fan so the airflow cools the electronics. As the fan wears, it draws more power. The regulator will shut the fan off if it is drawing too much power - which happens when the auto climate control ramps the aging fan up to maximum speed to cool the car down.

Symptoms are the fan stops for 1 second, or 1 minute, or 5 minutes - it's random. If the fan works fine when manually controlled on lower speeds, but cuts out when turned up to maximum speed, this is likely your problem.

A quick check is to pull off the left-hand dash endcover to expose the fuses there. Pull the 40AMP fuse and look for signs of heat damage - melting plastic and such. This is a sign the fan is pulling too much power. I had this problem in my 2004 c240 and while the fuse did not blow, it was melted and basically welded into the fuse holder. I had to get a new fuse and move it to a free spot in the fuse block.

BTW, a replacement fan and regulator run about $300 mail order, and are an easy DIY replacement.

There are a couple of threads in mbworld discussing this problem, search is your friend here.

LILBENZ230

Mine works fine in Auto mode, even at full blast never cuts out, as long as I have the manual dial set to at least the first notch below 1.

Shadow5501

Good input, that does sound like it's a problem in the control unit. My point is that if it quits in auto, and quits when you manually turn the fan speed all the way up, then you have a blower/regulator problem.

mleskovar

Both the fuses for the blower motor on my fuse map are 20A. and they both looked good. Does the blower fan physically start to get hard to turn when this condition comes up?

Shadow5501

Strange. On my '04 203.276 there is one 40A fuse in the dash fusebox which powers the fan. You can easily trace that it is the same wire running from that fuse straight over to the regulator.

I couldn't tell any difference between the old fan and the new fan. Given that it was getting to be summertime in Texas and I really like cold air, I ordered and replaced both the regulator and fan at once. Not willing to try just one or the other at the risk of putting up with no cold air for a few more days.

In my case after replacing the fan & regulator I was rather surprised and disappointed to find the new fan didn't blow cold. After exercising my mechanic's vocabulary for a few minutes, I checked for power at the regulator, and there was none. So went to the fusebox and found the damage described previously.

From what I can tell, this type of problem is not uncommon. Google up something like "melted fusebox" and you'll get a lot of hits, describing all kinds of cars.

johnkshop

had a similar problem with my 05 c230k with 105k miles. a/c would shut off for about a minute then automatically would come back. it didn't matter if i had the a/c at 0.5, 1, 2, or auto. dealer found the problem to be the blower motor regulator.