no heat on 1991 Chevrolet G Series Van (G20)

heater blows cold air when turned on.

by in Spokane, WA on October 13, 2010
3 answers
ANSWER by on October 13, 2010
themostat stuck open or heater core plug
ANSWER by on January 25, 2011
could be heater control valve located just in front of heater core
ANSWER by on May 06, 2014
I noticed mine blowing coldish on the feet only this winter when I took it for a trip.
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Van starts up and runs fine when cold. Sea light stays on. Once truck is up to speed it runs fine. When I give it gas it has a misfire. Temp needle doesn't move above 100.