hvac module

[JamesARBrown]

Hi does anyone have info on hvac and particular how it controls the stepper motor?

On stepper identified that

1) it moves to 4 positions, but only two matter

2) its position is identified by 4k7 pot which enables it to reach a position (demounted) without a physical stop

But when demounted it performs 180deg sweep... Is  this right at new? Do lotus really just let it pull constantly against physical stops.... Does not seem right

[LotuStuart]

Hi

I've had problems with this setup before, and do again.

with the arm removed from the motor (or fallen off) the shaft cycles endlessly between two positions when I put the vent selector switch to "AC". with the arm fitted, it used to jam up against one of the stops, and stop. I adduce from this that the end stops make a difference.

I think mines fallen off again-someone on here previously found a model airplane part that will fix my problem, so I'm going to try and find that.

Is it a b!tch to remove the stepper motor unit, clean up the pot and refit? My guess is "Yes, of course it F-king is" but might take a look at that....

 

 

[LotuStuart]

Having played around today...

stepper motor has three positions. 

Vac operated valve has two. 

Setting button has four positions 

on mine, 2001 MY, 

1-feet, screen and side vents

2-centre and side vents small bit of screen 

3-side vents, screen, small bit of feet

4-side vents and screen. 

I think my position 3 might be faulty and there should be more air to my feet. 

Or is this normal?

Also, the a/c comes on regardless of the 4 position sensor, and the air coming from the side vents appears to be cooler. 

My flap selector lever is broken, so I jammed it on as best I could and then tightened it on with a small jubilee clip. Holding at the moment. 

[LotuStuart]

Further to this, as there are three positions for the motor-and the motor controls a flap. 

Logically, the 3 position flap should be set to allow

air=up

air =up/down mix of both

air=down

so to set the motor/arm you have to point the selector to the mid position (which is blue arrow out) then position the arm in the mid point. 

I assume the HVAC module senses the stops by an over current and uses the variable potentiometer just to find a middle position. 

Next time I'm upside down in the drIvers footwell ill set it accordingly-this also means the Aircon will mainly blast out  oF the centre vents but also be directed up to the screen and down to the footwell a little which makes sense

finally, the side vents are always open. They can be controlled by closing them on the vents themselves. 

What doesn't make sense is that I have two positions which do the same thing. It's as if the control wire fr the motor flap is attached to my position 3, when it should be position 4. This way would make the symbols on the dial make sense and correspond to the way the air moves. Now I need to double check the hvac diagram and see if there really is a wire in the selector that does this! I doubt it. 

[LotuStuart]

Nb. The centre point is the one controlled by the variable pot as far as I can tell. Then the motor moves the spindle until it fouls on the end stops. 

I think the OP's diagram is not for the my2001/2 because the flap selector switch has three positions but mine has four. 

any comments on my posts appreciated. 

[JamesARBrown]

I think I concluded only two positions used by lotus on the stepper and they just let it push continually against the stop. There is a resistor in series with motor inside stepper and that prevents motor burning on lockup.

The final part of the solution is a separate vacuum switch and second flap (mine had a split elbow). I seem to recall on rhd it's on passenger side of airbox

 

Between the two valves achieves the necessary air flows

Last valve is vacuum mounted on top of airbox to do the recirc flap found under bonnet, and through bonnet is way to access it...cant see under dash

[LotuStuart]

The stepper motor definitely has a centre position. It is this that allows air to be split up and down. If the arm falls off, you can hold it in the centre position to confirm this. 

The separate vacuum switch controls air to the middle vents. 

The other vacuum switch controls he recirculation valve under the bonnet  

im taking my radio out at some point to see if I can work out the connections and how they affect it all  

 

 

[JamesARBrown]

Maybe.... sorry can't recall. I do remember selecting a switch position fitting the arm so it was right and then testing each way.
Yes radio out I put my arm through to hold screwdriver. Hard but much easier and more light.

 

[LotuStuart]

Thanks James. I took the radio out and have had a play with the switch but am no clearer. THere seems to 25k ohms in one setting!

ill figure it out.