Heater Blowing Cold air
CF Veteran
Joined: Jul 2009
Posts: 2,158
Likes: 11
From: Chico,ca
Year: 89
Model: Cherokee
Engine: 4.0
The vacuum for your heater controls comes from the vacuum bottle in the front bumper. It gets it source from the intake.
To follow it start at the intake on the back is a nipple with a vacuum hose that goes across the motor in the back and to the right front where the bottle is located,to see the bottle you have to look from underneath,it then goes from the bottle through the firewall just below the coolant bottle to the climate control actuater,it then goes back out to the heater control valve in the engine compartment. There are also lines under the dash to the blend door,defrost,etc.
To follow it start at the intake on the back is a nipple with a vacuum hose that goes across the motor in the back and to the right front where the bottle is located,to see the bottle you have to look from underneath,it then goes from the bottle through the firewall just below the coolant bottle to the climate control actuater,it then goes back out to the heater control valve in the engine compartment. There are also lines under the dash to the blend door,defrost,etc.
CF Veteran
Joined: Apr 2009
Posts: 4,734
Likes: 12
Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
The vacuum for your heater controls comes from the vacuum bottle in the front bumper. It gets it source from the intake.
To follow it start at the intake on the back is a nipple with a vacuum hose that goes across the motor in the back and to the right front where the bottle is located,to see the bottle you have to look from underneath,it then goes from the bottle through the firewall just below the coolant bottle to the climate control actuater,it then goes back out to the heater control valve in the engine compartment. There are also lines under the dash to the blend door,defrost,etc.
To follow it start at the intake on the back is a nipple with a vacuum hose that goes across the motor in the back and to the right front where the bottle is located,to see the bottle you have to look from underneath,it then goes from the bottle through the firewall just below the coolant bottle to the climate control actuater,it then goes back out to the heater control valve in the engine compartment. There are also lines under the dash to the blend door,defrost,etc.
The bottle is a vacumm reservoir. It probably has a check valve inside.
Junior Member
Joined: Jan 2009
Posts: 53
Likes: 0
Year: 1998
Model: Cherokee
Engine: 4.0L
I had this same problem with my heat last fall. It was coupled with my engine temp never really getting hot. I suspected my thermostat was broken/malfunctioning, stuck in the open position, and wasnt allowing the coolant to stay in the engine long enough to get hot... and the heated coolant outflow is what provides heat to the environment controls.
Sure enough, my thermostat was broken in full-open position, 24/7. Fixed the thermostat, fixed the heat problem.
Perhaps this is your issue as well?
Sure enough, my thermostat was broken in full-open position, 24/7. Fixed the thermostat, fixed the heat problem.
Perhaps this is your issue as well?
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