foggy windows and crappy heat,.
How is your coolant level? Heater core is first thing starved when coolant level drops. Air in cooling system can cause the core to become "air-bound" and not allow coolant to flow through it. Thread on this about a month ago. Also, make sure you clear the snow and ice away from the air intake for your heater below the wiindshield wipers. Bein' cold sux.
Like SSEBONNE4EVA said, you can narrow things down maybe by feeling the heater hose. Feel both of them and see if either one is hot. If one is hot and the other is cold, that implies that the hot coolant from the engine is not making it through the core. If that is not caused by an air block in the system, you may need a new heater core
If they are both hot (one a bit warmer than the other) that'* normal for a good heater core. That would point you toward a problem with air flow, maybe the air mix actuator that lets air flow through the core into the ducts, or one or more of the flaps not working right.
If they are both cold, or not very hot, again no flow through the core is indicated.
If they are both hot (one a bit warmer than the other) that'* normal for a good heater core. That would point you toward a problem with air flow, maybe the air mix actuator that lets air flow through the core into the ducts, or one or more of the flaps not working right.
If they are both cold, or not very hot, again no flow through the core is indicated.
Assuming your 99 is similar to my 95 (both should be series 2), stand on the passenger'* side and look toward the firewall. You should see two black rubber hoses (about 1" OD) coming out between the PS pump and the alternator. They go behind the right strut tower and in front of the AC dryer accumulator and then make a 90 toward the firewall where they connect to the barbs on the heater core. You may be able to get to them more safely by removing the relay center cover. Be careful when you try to feel these that you don't get your body or clothing too near the serpentine belt (!)



