No solution for you I think, sorry, but some insight:
blend motors are basicly servo's built into a gearbox with a variable resistor inserted into the housing. When the blend motor changes position, the gears also move the variable resistor to a different position. By putting a voltage on that resistor the HEVAC can measure the current/voltage and that way determines the position of the bled flap. The blend motors can be recalibrated by using one of the many P38 tools (I have a faultmate extreme for example).
Having said that, it seems unlikely that the HEVAC would not throw a maintenance book if the servo's were out of whack. The reason for this is even if the variable resistor would read differently or somehow was slower than the rest of the cogs, changing the HEVAC from LO to HI would force the servo's to run through the entire range from open to closed blend flaps. If the resistor were to lag behind, you would never reach the "high" end and the servo would jam, the HEVAC would detect a high current (stall) and throw an error.
I have recently had a similar experience though, it seems that the bled flaps never close properly and with a hot engine on a warm day, the air coming out of the vents seems pretty warm but not hot.
Anyway, I know of no situation in which a fault as you describe would occur, without throwing an error.
Cheers,
-P
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