Clicking noise in heater

There is a broken cog on the blend door actuator gear. As the small motor turns to adjust the blend door, the gear meets the broken cog and you hear the click. Once two or more cogs break, the door will no longer be adjustable. On later models (2003 I know of) the entire dash has to come out of the vehicle to replace the part which is about 50 bucks. It's a plastic motor about the size of a cigarette pack. Check the net for the repair procedure for your particular model - 1998. It may be positioned in a location easier to get to.

My 2002 heater makes a clicking noise when I turn it on and no hot air is coming out what is it?