Heater Dial Tooth Mechanism

[cRaig 273 1 Cars]

After refurbing my heater box, and swapping over to what (I thought) was a good dial mechanism/backplate, I've now discovered when I try to go from recirc to fresh air with the fan speed dial, the mechanism makes a horrible crunching noise, and then pops out.

Is it possible to swap the mechanism parts from one backplate to another? as I think the one I have is specific to the a/c spec, and therefore difficult to replace. Or has someone come up with a better solution? I don't think the problem is that my flap is too stiff (oooh err!) as it was fine when the box was going back together. Again, think the cable is fine, just a bit miffed now its all back together its stopped working!

 

Anyone else had a similar problem and solved it?

 

Did idly think it might be worth looking into 3d printing or machining the toothed parts in something more hardwearing..?

[farmer 328 1 Cars]

When my back plate played up, I changed the cog piece over from a spare unit I had.

 

One screw and it was swapped over

 

Servicebox does list a different part number for air con circuit boards though.

 

They are sided to work on a specific side on the board as I found out to my cost.

 

Fitted wrong side and it just wouldn't work something similar to your troubles.

[cRaig 273 1 Cars]

Cool, I'll try swapping the cog over, and will see how I get on. Thanks for that

[2-Pugs 57]

The problem is that the aircon and non-aircon backing plates are different, as you have found out, and the gear pieces are different. On non-aircon, you have from the top of the dial all the way down the left side to the bottom (sort of '7' position on a clock face) to move the flap from open to closed. So you have plenty of mechanical advantage with which to move a sticky flap, so to speak. On the aircon system, the system changes from fresh air to recirc mode in a very short gap at the top of the dial, so its essentially doing exactly the same thing, just over a much shorter distance, so the force required is much higher and the gear slipping you describe occurs readily.

 

It's a problem on every single one I've ever seen, and as of yet I have never really satisfactorily cured any I have owned, partly due to the inaccessibility of the bits when fitted in the car. All I can suggest is to examine the linkage carefully and lubricate and ensure there are no sticky joins, and do this before you fit the heater box, if possible.

[cRaig 273 1 Cars]

Thanks for the reply Rob. I am fortunate that I spotted this problem after refitting the dash box, but before refitting the dash, so can still easily remove the dial back plate to inspect. I will have a look at it, and see if it can be improved/repaired in any way. As you say, finding more aircon backplates is no easy task, so a more long term fix may be preferable!