I have the dash off my RR.
Q1. The blend and distribution motors were 90% ok before I started (periodic service book symbol), but anyway, now that I have everything out the HEVAC is showing me “Feedback circuit on RH blend motor faulty” (or some such – reporting via Nanocom).
I'm not an electronics expert, but possibly know enough to be dangerous. I can move the motors back and forth with a 9V battery. I took the 10k ohm pot off the board of the RH blend motor (ie desoldered it), and it goes all the way from 0 to 10k ohms (measured on multi-meter), but when I soldered it back to the board it goes from 0 to 3k ohms mid-range, and back to zero again (measured at the circuit board) - looking at the ETM there is a dotted line going from the pot to the motor, so maybe something is messing with the way the DMM measures resistance. Thing is all 3 blend motors seem to be like that (I didn't remove the pots from all 3 though!!). I’m just measuring this on a Uni_T multi-meter 20k ohm range – the fact that all 3 are the same may just mean my meter’s getting it wrong. Or maybe my test is wrong (just measured between the white/ wiper and one of the reference legs of the pot)?
Anyway – if the feedback error is not due to a dodgy pot then what else ? wiring? I think I may scrap the RH blend motor anyway, as the case has been cooked by a hot heater matrix manifold at some point (although the innards look fine ) but the principle is so simple that it then annoys me I can’t crack it !! As future-proofing I'm considering just installing 3 brand new ones at this point - just because accessing the blend motors is such a PITA.
Q2. Has anyone had any luck freeing the Distribution mechanism - I've greased all the pivots i can see, but it's still quite stiff - the gearing in the blend motor shifts it without complaint though. There seem to be two black toothed wheels driven by the main grey one, how do the black wheels come off ? Pull hard? I found a link to someone who had dismantled the whole heater box to do this, which i'm not very keen on.