97' F250-LD

iTrader: (1)

I was out driving the other day and noticed the amount of force coming from the dash vents was kinda weak until I let off the gas. Then when I stomped on it, it changed up to the defrost on its own. Does it on all the settings. Is that normal? Never noticed it in the past year and a half...

BrittonN

Mine has done that since I bought my truck. I have reason to believe it is caused by a vacuum leak.

jstockert

You have a vacuum leak. I had same problem with my truck when I bought it 8 months ago. Replaced vacuum hoses, and checked everything. Turned out to be previous owner put check valve in backwards.

97' F250-LD

iTrader: (1)

Good to know, kinda what I figured. I'll have to look at it eventually.