No heat unless on defrost setting, could this have something to do with a clogged/leaking heater core? I have been having to add small amounts of coolant every few drives lately, and have yet to find the leak. The car drives fine. I have never smelled coolant in exhaust before, however I am fairly confident that's not where it's going. White smoke upon start-up, not thick, goes away within a minute or two. I assume condensation? Has anyone ever heard of this, or experienced it? Any help/suggestions would be appreciated. Thanks in advance...

 

So you don't get any heat when you have it selected to blow to the floor? Your conditions are normal for cold starts and especially in cold weather.

Once your 7 warms up make sure you have the blower on the floor position. It's the only position heat will work. If it still doesn't work, you might need a new heater core.

 

Ha, I did not know that heat only worked on the floor or defrost setting... My car was completely warmed up, didn't notice until I was parked on the side of the highway, actually. Turns out, if you don't drive within the posted speed limits, you get pulled over...

I remembered heat from the other vents, or at least I thought I did Anyway, thanks for clearing that up.

 

To clarify, Mazda deliberately made the HVAC system of the car be such that the vents that deliver air to your face will only mix a small amount of warm air, this was done as studies at the time had shown warm air blowing on your face tended to make drivers sleepy. Other manufacturers have similar systems.

A lot of FDs seem to not have very good heating. There are a lot of threads about this. I am lucky I guess, mine is a small nuclear furnace. It wasn't always so, I had a severely clogged heater core that thru diligence and hard work I was able to get to flow 100% again. With the heat selector cranked to the far right, I get very warm...no, make that HOT air out the floor vents and defroster vents.

It isn't all that hard to check to see if your heater core is flowing good, if you have a small pump that will move some decent volume of liquid, like a Little Giant submersible. You just need to put the heat selector in the 'hot' condition with the car running, then shut it off. Now find your heater core inlet and outlet on the firewall and either disconnect those hoses or find where they connect on the engine. Basically you are going to get about a 2 - 5 gallon bucket and run one hose off the pump and one hose back into the bucket. Let's say you have a pump that will flow 12 gallons a minute, and you get a steady stream if you are just pumping freely thru the pump, NOT hooked to the car. Now, if you hook up to the car and see only a trickle or any reduced flow compared to your 'baseline', you can suspect a clogged core.

 

Exactly. Most Mazdas built around that time work the same way. I think its retarded as I want the heat where I want it. It seams to work best if you have it set to the defrost and floor position.