My logicon went out and I suspect the air mix motor. I have yet to test it, but my questions are semi-hypothetical, so just go with it...

1. Is the air mix motor rebuildable/fixable if it's broken or am I stuck with buying a new/used one?

2. If I buy a used one, is there a way to prevent it from breaking or increase it's longevity?

 

Probably depends on what's wrong with it - I haven't managed to get mine out to see if it can be split apart, but like the flipup headlights, if the problem is corrosion on the contacts you can brighten them up with sandpaper. I didn't have time to take the dash out, so I took a piece of coathanger, bent it and hooked it to the motor, push in for cold, out for hot. Yeah, it's ghetto, but it got me AC in the summer and heat in the winter until I get time to take the dash apart and get to it.

 

I just don't want it to screw up another logicon. I require heat!

 

I'm gonna go ahead and get another used one. However, I'd still like to know if there's a way to rebuild or at least make it more reliable so I don't lose another logicon.

 

Have you checked to see if the motor is good?

 

Sweet, you'll be in a prime position to find out. Once you put the new motor on, take the old one off and see if it's rebuildable. Just please post your answer back here for the next guy. (And me, I've got a blown air mix motor, too) Your procedure would be awesome, too!

 

No, but I'm getting a good deal on it and would like to have a spare to tinker with anyways.

Yeah, good idea... except there's a small problem. My knowledge of electronics is this big: |---|.

 

I'll help you out as best I can, but understand this is all theory of operation, your results may vary. - it's most likely just like a flipup headlight motor. Once you have it, if you can actually open it up, then it'll have a set of 3 concentric rings with gaps in (probably) the innermost and outermost. Like an almost closed C.

In a nutshell, if you apply voltage (it would be stupid if it weren't 12volts) to the outer two rings, the motor will turn on and make the little arm go one direction until it get to that gap (interrupting voltage and stopping the motor and the arm). Then putting the voltage on the inner two rings should make it go all the way the other way until it gets to the gap.

Those two gaps are full open and full closed on the door, which opens and closes the door between the blower directing air over the heater core or over the evaporator coils in the dash. Since you can have several settings in between, it may not look exactly like this, but I'd be surprised if it doesn't look very similar. You may have more rings and more gaps, for example.

Number one failure of this type of motor is those rings and the little metal arm contacts getting dirty. Hit them with contact cleaner and see if they clean back up to shiny. If not, use sandpaper or emery cloth to put the starch back in their shorts. Something pretty high grit though, because a rough surface will eventually build up carbon again faster than before.

The other common failure is that the metal arm contacts break off. Then you MIGHT be able to rig something up in their place, but test it thoroughly before reinstalling. Because if you make something work in that case, it'll usually fail pretty quick.

And if the motor won't turn at all (you can ohm it out with a multimeter and should get low resistance, but not zero, and definitely not infinity) then you're done. The only thing you could possibly do is find out who makes that motor and try to buy it from that company or find one that'll fit, which is again, usually more trouble than it's worth.

 

Good information. I'll try to get some pictures this weekend.

Where the hell is Icemark when you need him?

 

Or you could just put 12 volt to the lead that had the GR/W wire on it and ground to the yellow one. The arm should move all the way to one side. Reverse polarity and it will go the other way.

 

No need to take the unit apart. That worked for me.

 

I know how to test it, I just haven't yet.

My questions are:
a) assuming it is bad, is there a way to rebuild it?
b) if it's not bad, is there a way to help guarantee that it doesn't mess up?

 

The biggest cause of that failing (in my experience) is from the actual flapper being a pain in the nuts to move.

Reach up under your dash on the driver's side and disconnect the actuator rod from the flap arm...then try to move the arm (up for hot, down for cold) it should move like butter more or less. If it takes some good effort - thats what burnt out your air mix actuator.

edit: as far as if its rebuildable (the mix motor itself) beats the hell outta me, I would just buy another used one. I would *imagine* it can be rebuilt, but at what cost?

 

Well, considering a new one is ~$150... it might be worth it.

Like I said, I got another used one. But, I'd rather make an older one "like-new" than just put another 20 year old part on my car that's bound to fail sooner than later.

 

I just took mine apart and cleaned the grease off of the contacts where it had kinda scorched on there. It worked fine before I did that but I like to take things apart. I resoldered my logicon last night and now everything works except the air mix motor.
I think its the transistors on the main board. Where is Icemark?