Heater blowing cold air
 

Hello, new member here.. needs help on a diag, on a 99 Lincoln Navigator.
Cold day in colorado yesterday, turn on the heater, Heater was blowing cold air. all vents was cold.. what should I check first?. any information is appreciated.


thanks
Ariel

Could be the blend door, or a plugged heater core. Do a search for it and you'll find all sorts of info. If it is the blend door, here's one of the fixes for it. http://www.heatertreater.net/Lincoln...or%2097-02.htm

Is your coolant level low?

Either the blend door, which controls how much hot/cold air goes into the cabin, or it could be a plugged heater core which would prevent air from flowing through it efficiently. Some times the blend doors get stuck and require a little playing around with to get it unstuck, but sometimes it just needs to be replaced.

All vents? So even the rear passenger compartment? If so, don't bother with the blend doors. It's not likely both doors went at the exact same time. I would start with a thermostat replacement and burping the system of air. There are all sorts of posts on here regarding that.

If I remember correctly, the rear has a heater core as well. Hmmm, can't really say they would both go at the same time either! :) To check for a bad heater cores, you should already have signs of it on the passenger floorboard. It should be leaking. To check the operation of the heater core, find both hoses leading into the firewall that plug into the heater core. Start the truck, and both of these hoses should warm up about the same temperature and eventually get too hot to hold onto.

Report back your findings, and we can help you further.

Actually, this is a good first start. Many times, this could be the ONLY issue. I remember working in residential HVAC for my grandfather during the summers. I couldn't tell you how many calls we had that a refrigerator stopped cooling. Don't know if it was the kids or what, but their dial would be turned down low. We'd turn the dial up, and charge a service fee for driving out there. It was easy money....

My point is, check the easy stuff to save yourself time and money!