My 1997 F150 4.6 V-8 whenever you kick down on it or it goes out of overdrive the A/C goes into this recirculation mode and cuts air to the vents. But after it shifts back out or you let off of it, it comes back on. What is the deal? My dads V-6 doesn't do it.

 

Check and feel if the air is coming out the Defroster Vents when this happens. If it is, it sounds like the heater controls are running out of stored vacuum, and going to the default mode, which is the Defroster.
Could be slight vac leak under dash, or the check valve in vac line from engine not sealing tight to prevent backwards air flow under heavy throttle, or leaking diaphram in one of the vac motors, leaking selector switch, leaking vac reserviour (sp?) etc.
Needs more troubleshooting to determine what it is.

 

Granpa:
That is exactlty what happens. The air comes out of the defrost vents. What do I need to do? I guess I will have to take it to the dealer. Thanks,

kevin

 

My 1993 F150 has the same problem. It seems that at certain RPMs it will switch. The fan stays on but it doesn't circulate from the dash. I have noticed it go to the defrost mode when it does this. Are there any tests that I can do to further diagnose this?

There is one change that I am wondering might be effecting this. I have only had the truck 1 month. When I first got it, I checked the airfilter and saw that there was another smaller airfilter under the main airfilter. It was badly clogged so I threw it out in hopes of getting a new one that afternoon. I got the new main airfilter but did not get the small airfilter. Could that missing filter be causing the problem?

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[This message has been edited by justins (edited 09-26-2000).]

 

Granpa knows best.

Usually this is due to an improper connection or a faulty diaphragm.

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