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‘93- 305- Changes with heater during acceleration

1306 Views 20 Replies 4 Participants Last post by  mammadovn

Chevy Caprice 1993, 305.

Setting the heater to “heat” position, which blows to foot and when pressing gas pedal to “kick down” / hard acceleration, the heat start to come from upper vents. Heater speed is also increasing. It looks like the system loose vacuum somewhere, but cannot identify. Checked for vacuum leak at engine compartment with smoke - no leak identified.
Any thoughts?
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Might want to check if the HVAC controls can hold vacuum too.
'Supposed' to is the key word. I've seen a few controls where the seals in them or the vacuum lines to the various diaphrams no longer have perfect seals. Then they lose vacuum even with a perfect check valve.
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