Yes, I did search 'logicon failure.'

The car is a 1991 vert, fairly stock. I recently had the dash out to install a newer carpet, so that may have something to do with it.

basically, I'm getting a constant blast of very hot air coming into both driver and passenger seating compartments, it seems to be coming from where your inside knee sits (ie underneath the center console). At higher speeds it gets worse, and it has briefly stopped a few times, so it's intermittent. I've checked thoroughly under the hood, and don't see any torn grommets etc.....it sure as hell FEELS like engine bay heat.

I know my FD inside and out, but this is something different.....any ideas?

 

Check the shifter boots. If they are torn they will let heat and or trans fluid vapors into the cabin. Does the shifter get hot?

 

Is your heat shielding still in place?

 

The air diverter on the logicon will fail sometimes. This is a lever actuated by a servo that allows the cabin air to travel through either the A/C evaporator core or the heater core.

I have seen bad connections cause the servo to stick in the hot position.

The cabin air system take air in at the base of the windshield, the pressure at this point increases with vehicle speed, as does your natural air flow.

The shifter heat is mostly a stoplight issue.

 

Are all you logicon features working?

It seems if you took the dash out you have to move some of the vents. One must be undone letting air come in and pass the heatercore. Try looking under the dash and see if anything is loose????

 

Does the a/c work? And does it blow out the vents? Can you switch "modes", as in where the air blows out? What I mean is can you switch the air flow from the vents, to the defroster, to under the dash?
The heating/ac system consists of the logicon, the air mix motor, and the mode control motor.

 

Yeah, Check all the stuff you want but this problem is a shifter boot failure. Buy the rebuild kit from Mazdatrix and rebuild your shifter. might even put in their short shifter and your problem will be solved. I had this problem with my 89 GTU and finally listened to those that had had this problem and needed to replace the shifter since it was so loose. When I began tearing down the shifter assembly and took off the shifter cover, I could see my driveway! Nothing between the exhaust and tranny and the passenger cabin to keep the heat out but the cover. New boots will keep that hot air out of the cabin.

 

this sounds like your issue- I bet someone took them off as they start to rattle loose. Stock there should be one right on the firewall where it starts to head under the car, then over the converters themselves, and over the mufflers.

The shifter boots will usually throw alot of heat out the shifter and onto your hands- something im sure your used to with your FD.

 

Hey Rich! Fancy meetin' you here .

I'm with the other posters - it's either the air mix motor in the heater core that's stuck in a weird position or an exhaust issue. Since you just had the dash and everything out, I would moreso think it's a heater core problem of some kind.

I think the air mix motor is visible from the driver's side footwell, you can see and hear it move when you move the temperature lever on the logicon. Turn the key to On without the car running and test this out.

Supposedly Mazdatrix has seen a number of bad air mix motors, but they're not common in my neck of the woods - I've NEVER had to replace them, FC HVAC problems are usually bad solder joints in the logicon.

Dale