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Discussion Starter #1
Happy Christmas all..
I thought id spend some free time fixing the passenger blend motor problem on my 51 plate.

The motor wasnt turning at all so picked up a second hand one from fleabay.

On inspection the replacement motor had teeth broken so ive swapped gears from the original but im not sure on the setup.

The grear on the top of the Pot and the big gear that drives the heat control flap have small arrows on so presume there is some set up timing.

Ive guessed, but its not playing ball.

DO i need to reset anything ?

When I turn ignition on the motor looks for a home point. If I move the pot to about half way it will stop. Turning the pot left then right will make the motor change direction so I think the motor is ok. If the pot turns all the way around the motor stops and wont then turn until the ignition is turned off and on.

Cheers for any advice :mrgreen:
 

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No clue what a "51 plate" is. Such regional slang does not equate in the rest of the world. Please ad your Rover's year and model to your signature.

When assembled there are markers on the gears that must be aligned. On the home pages and/or previous posts Ron/P38arover showed how to change the gears.
 

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Discussion Starter #3
Its a 2001 4.0l "Westminster" edition.

Since playing a bit more..

The passenger motor moves when the driver heating control are adjusted ! Thinking now a control problem. ( have fit a manual rod for now LOL)
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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When controlling one side for temperature, the opposite motor will also move slightly. I believe this is to do with it's 'strategy' of there being a max of 8 degrees (Celsius) difference side to side. So to keep it within that, if you crank one side up, it will move the other side incrementally.

The gear position is as you have found with the arrows pointing to each other on the potentiometer gear, and the final drive gear.

Manually moving the potentiometer to the ends will probably put it out of the HEVAC's expected range. If a blend motor is thought to be out of range, or doing something strange, then it shuts down using that motor, and won't try to move it again until the ignition is cycled, as you've found.

If you are getting a lot of 'hunting' from the motor(s) moving back and forth, then it is worth checking the potentiometer - with a multimeter. Between the center pin (the wiper) and one end of the track you should get a pretty linear movement of between 0 and 10K ohms. If you move the second probe to the other end of the track, then you would get 10K back down to 0 ohms as the pot moves.

If you get any jumpiness or dropouts when it's moving, then chances are the track on the potentiometer is iffy, and that can cause many random problems with the HEVAC aswell.
 

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+1 on getting the small arrows pointing towards each other. This ensures the potentiometer knows where the output shaft is pointing.

Left & right flaps should move fairly independently, except when the L-R temperatures are set more than 6degC different.
 
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