Heater valve jitters

[FFMan]

One of the motors of the heater control in my 1994 Griff has the jitters. Its the one that sits in the left hand low edge of the passenger footwell, and controls a flap into the body.

I'm not sure what this one does, none of the controls seems to alter it any way, and it just jitters constantly. I've disconnected it for now but what does it do and what can be done to cure it ?

thanks

[DarkMatter]

It controls the fresh air/recirculating air flap, and from memory it should be operated by turning the lower left of the four 'heater' control knobs. The flap should be closed to draw 'fresh' air into the heater unit, otherwise it draws in air from the cabin.

You may need to move the battery out of the way to see the control closely, and you may find that a wire has become unsoldered. There it a potentiometer there and a couple of micro switches on the back. On my car the potentiometer had fallen off, I put it back and used a small amount of glue to hold it in place.

[FFMan]

my battery mount has been modified for easy access so i was able to get assembly off quite easily. i see the micro switches and the pot but all wires seem intact but motor does not turn when control is operated.

i guess i need to strip and clean and see what is going on. i expect the pot is at fault - are these available from somewhere ?

[DarkMatter]

FFMan said:

i expect the pot is at fault - are these available from somewhere ?

I think I've seen it mentioned elsewhere that they are a fairly standard item that you may be able to source from Maplin or RS.

Maybe you can dismount the potentiometer to see whether the motor goes round when power is applied. As I recall, when the potentiometer was hanging loose on mine the motor just went round and round.