A/C problem

[tipsymg]

I have a 2001 dodge ram 1500 pickup . When I turn the Air conditioning on it works OK , when I accelerate on the highway the air blows through the top ( defrost area). When I release the pedal you can hear a damper close and it blows through the vents again. When I accelerate it blows through the defrost area again. I've seen a few posts here that indicate a possibility of a vacuum line under the battery but I don't have cruise control and I think that is what those were talking about. I seemy main vac line off the intake and it has several check valves but they seem to be ok. Also the tiny vac lines seem ok also. Any suggestions on what else or where else to look?
Thanks!
Jeff

[Chris Stewart]

There's a little crack in one of those vacuum lines, you might re-check them.

[tipsymg]

Thanks Chris! I'll check them again. Wondered if the check valves might be bad, I'll check those too.
Jeff

[Chris Stewart]

Good idea on the check valve check, they should hold the ac door(s) vacuum up during low vacuum/acceleration periods.