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2001 c320, ac blower fan on all the time even with no key,

already replaced blower motor and...
2001 c320, ac blower fan on all the time even with no key, already replaced blower motor and regulator with new part, got it online, didnt work, bought a used part original, didnt work. Whats next?
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Answered in 5 minutes by:
4/3/2018
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 6,080
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
Verified

Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

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if you have a new regulator and the blower is still on all the time i would suspect the ac panel module .

that is the only thing that controls the speed request to the blower/regulator.

that or the wire is shorted.

let me check a diagram to see what wires to test.

Lou

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Customer reply replied 3 months ago
Thanks. Forgot to mention that already replaced panel with a used ebay part and didnt help.

ok, then this is an odd one lol

unplug the control unit and verify pin 13 white wire pink stripe has good continuity and no shorts to ground to the resistor

also pin 5 blue with violet stripe.

then if they test ok, i would clip them both one at a time, and do what we call a wire overlay, run your own wire from the ac panel to the resistor and see if the blower then functions correctly.

Lou

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Customer reply replied 3 months ago
Ok so i checked continuity on boths cables, was good, clip them but still the same. But i did found both are shorted to ground since ground wire 16 has continuity with both of them. Does it make any sense?

you cant check continuity through the module , are you checking with the module unplugged?

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Customer reply replied 3 months ago
Only way to make it stop is removing fuse num 30 from interior fuse panel

i have to step away for a call, i will return as soon as i can.

sorry for my delays

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Customer reply replied 3 months ago
Module is unplugged

i am back my apologies,

so with the module and the resistor unplugged do you have continuity to ground on either of the wires?

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Customer reply replied 3 months ago
i do have continuity. Already clip them and run new wires, same problem. As soon as i put fuse back it starts spinning like crazy

ok,

does it still run with the wires removed?

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Customer reply replied 3 months ago
Which wires? If i unplugged control panel it doesnt run

sorry, the wires from pin 18/5 that go to the resistor.,

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Customer reply replied 3 months ago
it does the same

ok, if those wires are not connected and it still runs that tells me its the resistor.

hmmm

where did you clip the wires at?

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Customer reply replied 3 months ago
2 inches from plug

plug on module side or on the resistor side?

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Customer reply replied 3 months ago
Both

ok, then there should be no reason for the resistor to supply power to the blower.

where did you get the new part from?

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Customer reply replied 3 months ago
New part its a cheap new part that i got online, then i got a used original part and does the same.

ok,

so on the resistor there are 4 wires yes?

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ok

  1. brown
  2. white pink stripe
  3. red green stripe
  4. blue violet stripe

those are the pins in order, can you verify?

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Customer reply replied 3 months ago
Correct.

ok,

is there a part number on the ones you have that are oem?

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and the blower should plug into the resistor , there are not any other wires tapped into the blower wiring right?

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Customer reply replied 3 months ago
Actually there are 2 black wires on pin 1 and 3 attached to a little black box

nope, can you send me a pic?

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nope, can you send me a pic?

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not sure why that sent twice lol

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ok, get those black wires out of there

they are not factory.

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looks like they are jumping power and ground FROM the blower to whatever that black box is, can you see where the other end of those wires are going to?

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shoot maybe capacitor lol

that is the problem, it HAS to be.

maybe they did that to help dry the ac system?

customer has to know something.

this dont fall out of the sky and install itself lol

clip a wire, it has to be it. i bet its a capacitor.

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whats the part number on there?

i can see beru, cant make out the number.

that is not in my wiring diagram and i dont ever remember seeing those.

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Customer reply replied 3 months ago
No luck!!! Cut it, soon as i put fuse back start running like crazy with no key on. Tried with 2 different blower resistors.

hmmmm

what is your vin?

and the part number of the resistors that you have?

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Customer reply replied 3 months ago
WDBRF64J51F108008Part number ill send it later. Even with the original does the same

right understood.

this is a good one.

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A2308216351

oem part number

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let me opt out. i think the resistor is the issue , even though you have a new one or used one.

but i am not there to diagnose and i am not sure what else to try since you clipped the wiring.

to me if you clipped the wiring it should have stopped blower activation.

best of luck, please let me know how you make out.

hopefully another tech picks this up.

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Customer reply replied 3 months ago
Thanks for your help.
Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 55,216
Experience: Bosch Certified Master Tech. Over 35 years experience.
Verified

Hi, different expert here. My name is***** you still need help with this?

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Customer reply replied 3 months ago
Hi. Yes i do.

Ok, let's bench test the blower regulators. Remove the regulator and connect ground to terminal 1 and 12V to terminal 3 in the 4 pin connector then measure the voltage at the 2 pin blower connector. You should not have voltage at the connector. If you measure 12V your blower regulator is defective. Make sure you connect power and ground to the correct terminals. They are numbered in the plug.

Let me know what you find.

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Customer reply replied 3 months ago
Ok. Just checked the original regulator and the new one i bought online and none of them have voltage on pin number 2.

Not sure if you understood the instructions. You need to put ground to terminal 1 and power to terminal 3 then place a voltmeter across the 2 pin connector where the blower plugs into the regulator and measure the voltage there.

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Customer reply replied 3 months ago
i understood. Used power probe to put ground on pin 1 and power to pin 3 and used voltmeter to check voltage on pin 2 and had no voltage.
Customer reply replied 3 months ago
Hold on one swc
Customer reply replied 3 months ago
Now i understand, got confused with pin nunber 2
Customer reply replied 3 months ago
Alright, all 3 regulators have voltage at the 2 pin connector.

Then all 3 regulators are bad.

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Customer reply replied 3 months ago
Lol ok. I will get a new one original and let you know. Thanks.

You're quite welcome.

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Customer reply replied 3 months ago
Just got new one i bought, i did same test with same results, im still getting volatge on the 2 pin connector. So just to make sure im doing it right, im using power probe, ground to pin 1 and power to pin 3, now voltmenter black on battery and red at pin inside 2 pin connector, and i get voltage.

You need to put your voltmeter across the 2 pins in the connector for the blower.

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Customer reply replied 3 months ago
i guess i was checking it wrong, voltmeter across 2 pins has no voltage

Is that the case on all of the regulators? Make sure that the brown wire in your 4 pin connector is going to pin 1 and that the red/green wire is going to pin 3 on the regulator.

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Customer reply replied 3 months ago
Good morning. The cheap new i got online has voltage, the original one i got yesterday has no voltage but it does the same, blower keeps running.
Customer reply replied 3 months ago
Just found that white/pink wire coming out control panel, has voltage all the time even with no key.

If you disconnect the climate control panel does the blower turn off?

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Customer reply replied 3 months ago
it does
Ok, did you reinstall the original climate control panel along with a good regulator?
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Customer reply replied 3 months ago
I did it and it does the same.
Customer reply replied 3 months ago
Update. Control panel has 2 plugs, small plug with 3 wires, if i unplugged that, everything works fine. One cable has ground and the other 2 wires low voltage. Is that right? Any ideas?

What color are the 3 wires?

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That small plug is for your flap positions. It shouldn't be affecting your blower motor. You should measure 12V from pin 1 to 3 in the small plug.

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Customer reply replied 3 months ago
Pin 1 brown - ground
Pin 2 red/black - 2.2 volts
Pin 3 blue/black - 3.0 volts

You should measure 12V from 1 to 3 with the connector plugged in. You should have no voltage on the 3 pin connector with it disconnected.

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Customer reply replied 3 months ago
Those readings i sent are with plug disconnected.
It sounds like that harness may be connected incorrectly. Was any work done in the dash?
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Hi, just checking in. Did you ever get this figured out?

Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 55,216
Experience: Bosch Certified Master Tech. Over 35 years experience.
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Marty and 87 other Mercedes Specialists are ready to help you
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Customer reply replied 2 months ago
Hi. You were right, that 3 pin plug was connected incorrectly, apparently car had work done before. Right plug (black wires) was hidden behind radio. I ended up replacing control unit as well cause it wasnt working.
Thanks for your help!!!
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