Hey all,

So the other day I noticed when I started my car (2000 3.8 V6) that my AC was blowing full blast on defrost. The problem is I had it turned all the way to the left at Max AC. After it idled for a while the air shifted to the regular blowers, but when I hit about 1800 RPM it would shift right back to the defrost blowers and stay there until I slowed down. I think it kicked into defrost randomly once, other than that it's when I start to accelerate.

What's up with that? I live in Texas and I keep it cranked to the highest fan speed on Max AC pretty much all the time to keep cool for the hottest couple of months. Anything I should check in to?

 

Not sure about the 2000, but some blend doors move with vacuum. You might have a leak somewhere. Sometimes the blend door will break, that means a whole new heater box. If you pull the glove box, that might give you access to the motor, if it's electric, pull it off and find out what's underneath. Should be a hex shaft.

 

Look on the passenger side firewall where the heater core hoses exit and you will see a vac line. It comes out, goes across the back of the motor too the vac tree and is a common problem for breaking or leaking. Give it a good inspection and I bet you will find your problem.