Nissan Repair: heater, vacuum system, faulty valve

Question
i have an 2005 frontier. my heater only works when i travel above 40mph. below that it just blows cold air,the faster i go the hotter it gets. once i slow for a light or whatever it goes to cold air again

Answer
Hi Joseph -

I would check the operation of the heater control vlave, located in line with the heater hose, usually near the firewall. The system is run by vacuum 90% of the time, so there could be an interruption in the vacuum system, or a faulty valve.

Hope this helpa -
aloha
calvin