Heating issues

[Cool_Steve]

There are two first gen's in our family, mine and mom's. As they have aged we've sometimes had the same issues with our cars, and other times we've had different issues. My car every winter has made great heat inside the cabin. Two winters ago mom's Protege could just reach luke warm at best after a long time, it is still like this today. So far she's replaced the stat, the rad (due to common top cracking), its gotten new coolant, and the heater core was blasted out but with little results. She doesn't want the dash ripped apart and the $600 out of her pocket to get a new core.

The little fuse box below the driver's dimmer control - on the black diagram box it says '30A heater', does that relate to the heating system? Or just the blower motor or rear defog? Something I'm not getting - I pulled the cover off, saw all the fuses where they should be...but I see no 30A fuse. Says it is there on the diagram box, but the only thing above the fuses is a black thing, which is the breaker, correct? So where is the heater fuse? I'd like to know because I can easily junkyard the fuse.

Her car also has A/C - it died too, it engages when you press the button but doesn't make cold air, I assume the gas leaked out. Is it true that when an A/C system leaks/breaks, it will affect the heating system? Because it was that summer after that the heating issues started. And I really hope the same thing doesn't happen to me, because my A/C two summers ago while cold, was much colder years before.

[1Mazda323Fan]

Sounds to me like you might have a blend door issue here. It's possible the flap is stuck or jammed and won't allow full airflow over the heater core. I have no idea where it is exactly on BGs, so you'll have to rely on others with more experience there for a location. Sorry. But that's what I'd say is going on here. It's that, or: 1)the heater core is still blocked up, and will need serious cleaning/replacement; 2)the coolant level is low, either due to leaks or an air pocket in the system. You might want to try bleeding the system to make sure.

As for that heater fuse, unless Mazda did something really weird, it's most likely for an auxiliary heater that's available in some markets, generally in the really cold regions. If your car doesn't have that option, then the fuse would be absent. I seriously doubt it's for the heat you get coming from the vents, as that's produced simply by blowing air over the heater core, which uses engine coolant to heat up the air.

I've never heard of the A/C effecting the heat in a car. They're two separate systems. They run on roughly the same principle, just opposite ends of the temp spectrum, but they should be completely separate from one another. As far as the air con not working, yes, you most likely have a leak somewhere (assuming the compressor turns on). Check the condenser in the front of the car (it looks like a small radiator, and is in fact in front of the radiator) and make sure it's not blocked with leaves/bugs/small children. If it looks good, you'll have to take it to a shop and have them dye test the system, or you can do it yourself if you feel you can. The necessary supplies should be available from most any auto parts store. The condenser, compressor, and all the seals in the A/C system are the biggest points for leaks. Oh, almost forgot. If it has a thermal expansion valve (TXV) in the system, sometimes that can get clogged or start leaking as well. I'm not terribly familiar with the exact setup on first gens, so again someone else will have to fill in here.