Short blasts of cold air

[PWRSTROKE06]

Hi there,

I have an 06 F-350 dually with electronic climate control. When I have the heat blowing and I climb a hill or accelerate the heater stops blowing hot air and gives a few seconds of cold air then goes back to normal. Motor is running in normal range for temp. It feels like this is a vac. problem? If so any ideas on what to look for?

Thanks for reading and any advice I can get.

[joshmrn45]

I experienced the same thing a few weeks ago. I have a 07' F-250. It happened after accelerating quickly getting on the interstate. All the gauges where at normal temp and engine was running fine and the heat was hot, but suddenly turned cold for about 10 or 15 seconds then went back to hot. I'm not sure what could be causing this. Only happened that one time, and it was very cold outside, a few degrees below 0.
Any ideas would be appreciated!