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Discussion Starter #1
I true fashion, something fixed, something else gone wrong - please someone tell me if I am having fun yet!

RAVE talks about the BeCM controlling the speed of the blower fans, but I have not yet figured out if the actual speed of the motors is controlled by the BeCM directly or via a relay somewhere - Im guessing it could be a relay as in operation the rpm is not infinately variable but increases in steps?

Mine have been a bit intermittent in operation, and now are pretty much not working at all, the actual motors are free to turn and 12v is present at the red lead/black lead on the motors so why dont they turn? Does the BeCM provide a sort of Pulse modulated signal to vary the motor speed - this may explain why there is voltage but no rotation? It is possible that both motors have failed together but a bit unlikely methinks?

There could be a loose connection somewhere as it I give the rangie a good thrash up my very rutted farm drive the motors occasionaly fire up and work as they should. Without the engine running I can hear a sort of click from the RH motor housing as if some sort of thermal overload switch is tripping out shortly after the HVAC fans are selected on in manual with ign key in pos 2. If a themal swith is in there this suggest the motor is faulty? - not yet figured out if this happens on the LH motor too

Does anyone have intimate knowedge of how the fans are controlled, how robust the motors are, also, does the HVAC system need a signal from the coolant temperature sensor before it will signal the blower fans to come on? my truck has 120k miles.

On the posative side my distribution motor and blend flaps are now 'unstuck' `) and I have seat back heating `) - if not a warm bum yet, all thanks to this forum! Cant imagine what I would have been doing without this resource!! Perhaps ignorance is bliss :p

Gordon
 

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1995-2002 Range Rover P38A
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Hi

In the motors are speed controllers. Via the hevac ecu a signal towards the blowers is given. The lower the voltage from the ecu the higher the fan speed. The electronics inside the motors, supplied with the 12 VDC from the black and red wires will output the difference voltage between the ecu and the 12 VDC.

If you have your fans coming on after driving over a hump, this indicates that the carbon brushes inside the motors are gone and need replacing. In some other posts I have given some info on how to open the motor and how to change the brushes complete with some photos.
I am on a very slow internet connection now so can not give you the links but do a search and you should be able to find them.

Good luck

Jos
 

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Discussion Starter #3
Great, that looks just what I need, I did search earlier but found nothing - I will look more closely this time.

Thanks again.
Gordon
 

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Discussion Starter #4
I found the photos Jos posted. Can I test my blower motors in situ by running a lead from the neg terminal on the motor direct to the chassis? my thinking is that if the motor speed is determined by the voltage difference between the red and black wires if the black is earthed direct to the chassis then the motor will see the full 12v difference and run at full speed???? - assuming the motors are good of course.

Or will I blow something [expensive] up?

Gordon
 

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1995-2002 Range Rover P38A
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Hi

If you disconnect the connector towards the electronic control and apply a path to ground from the black connection on the motor (direct connection from the carbon brushes) towards the chassis the motor should run on full speed.
To test this check first if you have the 12VDC on the red connection. If not then check relay 6 or 7 and fuses.

Make sure that you do disconnect the electronics as you could short them and cause damage to components. The motor is designed for 12VDC operation and will be able to take the 12VDC without any problem.

Good luck.

Best regards

Jos
 
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