Help I can't switch the Blower off! (W140)

[callum]

Hello ,

1992 500SE (W140)

I need some help here!

I fitted a new regulator on my AC/Heating Blower yesterday.

Brilliant it sprang to life and everything seemed great, not at all, i now can't switch the blower off without disconnecting the battery.

No matter the position of the switch, Min Auto or max it blows full pelt.

Is there a relay somewhere before the regulator, that someone knows about?

I tried all the fuses associated with the blower, even removing these doesn't switch it off.

Surely the new regulator can't be faulty as well?

Anybody any ideas???

Thanks in advance

Callum

 

[BlackC55]

Mega money those regulators.

This is a strange one. Put the old one back on. Be careful not to touch that white grease as it is carcenagenic. (spelt wrong I know) and see what happens.

 

[callum]

Thanks

Thanks Mate,

I am now at a loss again, I refitted the old regulator, now the Blower works! albeit at a very low speed, but it works, even more confusing.

Now i can at least turn the blower off with the ignition and the 0 button

just wish i knew what was going on, and why would a new regulator cause the blower to run continuously even with the ignition off?

but at least i can get heat now and clear the windscreen.

Thanks again

Callum

 

[Diesel Benz]

Can you confirm that the new regulator was a new one, not a used part? When my blower regulator failed on my W210, the blower went to full speed (the regulator may get short circuited when it fails, often the case with semiconductors).

Can you disconnect the control line and test it (measure the control voltage)?

 

[callum]

New Regulator

Hi Mate,

definitely a new regulator, out of a sealed bag from rotogrip in Birmingham.

i dont have a meter to test the voltage, but surely a good idea, and probably the first thing a garage would do.

strangest thing this original regulator didn't work at all before, now does at slow speed.

could be short lived, same thing though, the min auto max wheel has no effect on the blower speed.

Thanks for the advice, and you are right, checking the voltage would help.

Callum

 

[grober]

read this article http://www.mercedesshop.com/Wikka/W140BlowerMotor

heres some sample quotes :- REMEMBER - there is power to the motor even when the switch is OFF. The blower motor on a 140 is controlled by the NEGATIVE pole. I understand that a lot of cars use this same technique. So the closer the negative on the motor is to a short circuit (0 volts), the faster the motor runs. Keep that in mind.

Remember - these motors are controlled by varying the ground potential voltage - NOT the positive voltage. The positive voltage to the motor is always a direct circuit to the battery (via a relay/fuse I believe). It's also hot all the time and never switched.

 

[callum]

thanks mate,