cRaig 273 1 Cars Posted January 2, 2015 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..? Share this post Link to post Share on other sites
farmer 328 1 Cars Posted January 2, 2015 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. Share this post Link to post Share on other sites
cRaig 273 1 Cars Posted January 3, 2015 Cool, I'll try swapping the cog over, and will see how I get on. Thanks for that Share this post Link to post Share on other sites
2-Pugs 57 Posted January 6, 2015 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. 1 Share this post Link to post Share on other sites
cRaig 273 1 Cars Posted January 6, 2015 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! Share this post Link to post Share on other sites