dipping rear view mirror

[Marshall]

Just another P38 question...

when I reverse, the side mirrors dip, and when I go forward again, they should come back up to the right angle... The problem is, they regularly either go back to a randomly selected angle, or keep moving until they can't move anymore... This would happen in about 25% of cases.

Any idea what's wrong?

[p38arover]

Possibly faulty feedback potentiometers in the mirrors.

If they weren't coming back at all, I'd suggest broken ball couplings on the racks.

Good ball joint:

https://www.aulro.com/afvb/images/imported/2011/07/1027.jpg

Broken ball joint:

https://www.aulro.com/afvb/images/imported/2011/07/1028.jpg

[Marshall]

Thanks Ron,
would this just be a question of a clean or would new ones be required? Are they even available? Or is a whole mirror required?
Pete

[p38arover]

I've not pulled one apart, Pete.

I doubt one could clean the pots but they may be replaceable. I'll grab one from my local LR workshop and see if one can access the pots. Hang on, I may have one in the garage. I'll have to have a look.

In the meantime, you can turn off the dip feature.

[p38arover]

This (from Rangerovers.net) might be useful:


I think you're all barking up the wrong tree!
The symptoms described match problems I had with both mirrors when I purchased my HSE a year ago.
Plenty of readings and many tests later the faults were diagnosed.
But first - How it works...
Vertical and horizontal positional data (analog voltage) is fed back to the electronics from embedded ceramic potentiometers (pot) within the motor drive sub units in the mirror assembly. When reverse dip is selected there is a dc offset applied to the feedback loop to reference the new dip position. This only applies to the vertical adjustment. When reverse is deselected, the offset is removed and the motor runs until the feedback pot provides the original position. This is called a servo circuit.
Common fault is that the ceramic feedback pots crack / break. This means that the mirror dips using the stored offset but gets lost when the offset is removed as there is no feedback. I tried superglue, epoxy fibreglass but each time I tried to rebuild the motor sub assemblies the ceramic backplate cracked. Doner unit provided the parts in the end. Works a treat!

[Marshall]

guess I will have to pull the glass off this weekend and have a look... but it definately sounds like I need a new "pot"

[p38arover]

If the pots are integral with the motor, then it won't be an easy fix.

[Marshall]

Is there a way to disengage the automatic dipping feature of the mirrors (when reversing), but still be able to use the switch to adjust them if necesary?
How does the mirror know that you have selected reverse? is there a wire running from the gearbox selector or is it from the ecu?

Pete

[DT-P38]

Is there a way to disengage the automatic dipping feature of the mirrors (when reversing), but still be able to use the switch to adjust them if necesary?
How does the mirror know that you have selected reverse? is there a wire running from the gearbox selector or is it from the ecu?

Pete


Hey Pete,

That function is user programmed.

Refer to your owners manual for instructions on how to set the mirror dip function to the level you want... it can stay same or dipping to whatever you want to set it at.

Hoo-roo, Dave