heater

[transit lee]

ive got a 1999 L W B transit
when im stationary with the heater on it blows
from hot to cold if i rev it up it then blows hot again
& sometimes when im driving along it blows from hot
to ice cold then clears itself & blows hot again
is this a air lock ?
if so how do i overcme this problem ..........

[winterheating]

more likely water pump

[ake]

more likely water pump

I would agree