Mountaineerfan 44 Report post Posted June 5, 2020 What is this black canister/valve that is connected to a line going into the firewall as well as to the heater hose that is going into the heater core? Quote Share this post Link to post Share on other sites
LoneWolf2U 136 Report post Posted June 5, 2020 Vac control valve for heat. it opens/closed coolant flow to heater core. 1 Mountaineerfan reacted to this Quote Share this post Link to post Share on other sites
danno 128 Report post Posted June 5, 2020 You want all that hot water to stop going to the heater core when the AC is on. So it is supposed to stop it. The reality is it usually only slows it down. 1 Mountaineerfan reacted to this Quote Share this post Link to post Share on other sites
Caseyrhe 650 Report post Posted June 6, 2020 Heater control valve 1 Mountaineerfan reacted to this Quote Share this post Link to post Share on other sites