Air Con fan stays on even ignition switched off

[JJ CLK430]

Any help or advice would be greatly appreciated!

The air con fan on my CLK430 (2000) won't switch off even when the ignition is switched off which in turn keeps running my battery flat. I have had to disconnect the battery now and can't use the car until I manage to fix it

Any ideas?

 

[daves_trip]

on my '97 c230, the same thing happened when the air intake for the heater/air con filled up with debris from the trees in front of my house, plugging the drain holes. the whole front floor filled with water and I am still having problems because of that. the grill in front of the windshield should come off allowing you to clean out the drain holes that prevent this potentiall expensive damage from occuring. under the passenger side dashboard (glove compartment) there was a plastic cover easily removed revealing the heater motor box and pollen filter which were both filled with water.

not sure about your model but I don't imagine that they reinvent the wheel each time. I did the same thing as you, disconnect the battery until I could look at it. after dryin git out the heater went back to normal and some but not all of my warning lamps went out.

now my guages stopped working... f***...

 

[JJ CLK430]

Thanks for the advice.

I will check this to see if this is the problem. I had assumed it was purely an electrical fault but I am certainly no expert on these things!

 

[JJ CLK430]

No Joy So Far, Any Other Ideas?

No joy I'm afraid - have checked the drain holes which appear to be completely clear and I can't see any signs of water in the pollen filter or heater motor box.

As far as the a/c control panel is concerned, i can change temperature ok but the blower is stuck on full whether i have the fan control on 'auto' or any setting between 'lo' and 'hi'. if i switch it to 'off' the fan keeps going but with a different tone (and only blowing out of the middle vents) which i assume means that the a/c controls work, just not the fan control.

does this sound like a fault in the heater control panel and if so would this be something i could fix or replace without having to involve a dealer? recent dealership experiences have been anything but pleasant so i would like to avoid if poss...

 

[petes350]

Try taking the fan fuse out (if you can find one) so at least you'll be able to use the car.

The contacts in the fan switch may be broken or (perhaps a relay, though I wouldn't of thought there would be one).

Other than that, I'm afraid I don't have any other ideas.

 

[jberks]

The fan is controlled by an electronic regulator. The switch, whether digital or manual simply sends a small variable voltage to the regulator which then controls the fan speed. when they fail, these can make the fan do anything, including run flat out all the time or even speed up and slow down randomly.

Its pretty easy to test if you can find it - on the E its under the fan cover in the passenger footwell. It has a 3 pin multiplug - 2 for power (+-)and 1 for control voltage. At the sides there are 2 spade connectors feeding the fan. If the switch voltage is 0 and the output at the spades is still a full 12v - you need a new one.

 

[JJ CLK430]

Thanks very much for all your advice.

I tested the electronic blower regulator as recommended and it had indeed blown. Have now fitted a new one and all's well again!

Thanks again.

 

[sporty]

JJclk430- Have u any pics of ur 430 ? how many miles has it done?

 

[Jinksy]

Heater fan stays on

Hi Guys, I am a Benz mechanic in Australia and I too have had the dreaded fan issue, I just wanted to say thank you for the advice on the regulator as I was able to quickly repair my customers car where star diagnosis was unable to assist me. I had another fan issue with a C class 1998 W202, the fan would stay on full no matter where you selected the speed at the switch, except it would turn off when the key was turned off, Turned out to be the actual switch panel as the temp wheels were making heat no matter where they were also. I replaced the control unit and all was good again.

 

[television]

Hi Guys, I am a Benz mechanic in Australia and I too have had the dreaded fan issue, I just wanted to say thank you for the advice on the regulator as I was able to quickly repair my customers car where star diagnosis was unable to assist me. I had another fan issue with a C class 1998 W202, the fan would stay on full no matter where you selected the speed at the switch, except it would turn off when the key was turned off, Turned out to be the actual switch panel as the temp wheels were making heat no matter where they were also. I replaced the control unit and all was good again.

Hello and welcome,, another fault where the engine fan runs all the time, is water in the front SAM in the fuse box

 

[Zorgos]

I had same kind of problem. one day i just found my car with dry flat battery. When i got new battery and installed it i noticed that fan is running with engine off. Well make long story short i did search forums and found that sensor may be broken or burned. So i got new one replaced it and Bingo its working perfect. aha for few month. then one day finishing work getting to my car trying open the doors and ..... battery is dead. Borrowed booster from friend, boosted it up car starts and blower run on full blast. While driving home its went back to normal (you can hear it by the nose and speed) when i got home i decide to not take a rist and just pulled out the fuse. So only solution comes on my mind is to put some sort of interrupter on the positive poser leading to the sensor. It solved the problem but speed of the fen is excessive. So I am just wandering. its cant be just a sensor. Some thing else causing this problem. New sensor died in about 2 month no way. I do not see any signs of water in there. Does any one have any idea what could be the problem beside the sensor or what cause sensor to die?

 

[television]

Water can get into the control box down behind the front bumper.

 

[Zorgos]

Hello and welcome,, another fault where the engine fan runs all the time, is water in the front SAM in the fuse box

hi there. Can you be a bit more specific where is that box? just to make sure i am looking at the right spot.

 

[television]

Follow the wires down from the fan and they go to a box behind the front bumper.

 

[Zorgos]

hitter blower fan is under the dash there is no way to follow the wires lol

 

[television]

So you are talking about the heater fan motor, this can only be the reg pack short circuit if the heater motor is running when all turned off.

 

[Zorgos]

exactly. one of the problem was the sensor what is sitting on the motor under the dash. but after i replaced it it lust for 2 month and same problem started again. So I am just wandering what can cause this.

 

[television]

This reg pack must be mounted on a clean surface using heat sink compound.

There are some fakes floating around

 

[Zorgos]

Yes I know that part. but even all that did not prevent it from damage in short period of time.

 

[television]

If the heat sink was not good it would overheat and self destruct