Air vents change under heavy load

[EdmondsXLT]

I've been noticing something strange with my 03 XLT this summer on our road trips. At heavy load, typically going uphill at 60mph or so with the AC on, the vents will change on their own, then revert back after the road flattens out.

I'll have the vents set to blowing straight forward or maybe footwell and forward mixed. The AC is on and fan speed is at 3. It's 85+ degrees out. We're on the highway and start going uphill at 60 mph and then the air will switch to defrost mode and start blowing on the windshield. When the hill levels out the air will start coming out of the correct vents again.

Is this normal? I've only had the Explorer for a couple of months. Is this a vacuum issue or something?

03 XLT, 4.0 V6
175k miles

 

[974X4BLACKSPORT]

This would be a vacuum issue, usually the vacuum resivour is leaking or the hose connections and/or hoses themselves leaking.

 

[swshawaii]

Vacuum control valve? (Check valve)
No HVAC while accelerating

2003 FORD EXPLORER 4.0L V6 Vacuum Control Valve (VCV) | RockAuto

 

[gtyates]

What swshawaii said. Just had to replace this part on my sons' '04. Took about 2 minutes to do.. and it solved the problem.

 

[EdmondsXLT]

Awesome, thanks! Just ordered one up, I'll let you know how it goes.