Good morning,
I have a 1997 chevy astro van my rear heater is blowing cool air ( i do not have a rear A/C ) front heater is ok , i change the rear heater core still blowing color air " is their a sensor or a regulator ... thanks for your help

doug, October 2007

my name is rudy.have the same problem i been reading about it and it seems like is probably the vacuum control valve

rodimiro, December 2009

may not be an answer but I have he same problem - I changed the water pump last fall and now all I get is cold air out the back but the front heater is hot - is therea petcock? I even had a GM dealer tell me there was a circulating electrical pump under the van but I did not see it - mine also seems to have cold lines leading to it when looking up from the bottom.

Bob, December 2007