Not engine, but probably mechanical
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Joined: Jul 1999
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From: Dolores, Colorado
Not engine, but probably mechanical
Does anyone know why my climate control will only blow out the defroster ports. This is in any mode. Sometimes if I put it on AC max and then switch it to vent it will blow out the dash vents, but on heater forget it.
I have disconnected all related AC components under the hood and removed them.
Thanks for the help.
I have disconnected all related AC components under the hood and removed them.
Thanks for the help.
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Joined: Jan 2000
Posts: 19,651
Likes: 309
Dark,
The air control doors in the HVAC system are positioned by vacuum actuators. When the system was working properly, you should have heard a slight "hiss" when control positions were changed. Vacuum is applied to one side of a diaphragm to move a damper. A spring in the actuator returns the damper to the default position when the vacuum is removed. When the system is in total default, air will discharge through the defroster outlets only.
This sounds like your situation. It is caused by a lack of vacuum to the HVAC controls or a failed vacuum switch/valve in the HVAC conrol head on the dash. The vacuum is routed through a small plastic line through the firewall and to the control switch. The control switch is nothing more than a multi-ported valve that applies vacuum to a given outlet at a given position. You turn the control to heat, and the vacuum is routed to the heater air door. Vent position routes vacuum to the dash vent air door, etc. Again, when no vacuum is present, all air discharges through the defroster outlets.
Check for a small hose near the firewall that is disconnected, kinked, melted, cut, or otherwise damaged. On a TPI engine, the vacuum source is at the fitting on the right side of the plenum, directly behind the vacuum fitting for the fuel pressure regulator. If you do not find a hose problem, you'll have to remove the control and check for vacuum at the control switch/valve. If a vacuum supply is present, turn the control to different positions to test whether vacuum is ported to the correct line in a given position. If the vacuum just leaks out all around the control, you'll have to disassemble, clean, and regrease the control valve with silicone grease. You could replace the control, but it is likely a dealer-only item that is not in stock. Unless the control is completely broken, I would try the cleaning and regrease. It's worked for me.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
The air control doors in the HVAC system are positioned by vacuum actuators. When the system was working properly, you should have heard a slight "hiss" when control positions were changed. Vacuum is applied to one side of a diaphragm to move a damper. A spring in the actuator returns the damper to the default position when the vacuum is removed. When the system is in total default, air will discharge through the defroster outlets only.
This sounds like your situation. It is caused by a lack of vacuum to the HVAC controls or a failed vacuum switch/valve in the HVAC conrol head on the dash. The vacuum is routed through a small plastic line through the firewall and to the control switch. The control switch is nothing more than a multi-ported valve that applies vacuum to a given outlet at a given position. You turn the control to heat, and the vacuum is routed to the heater air door. Vent position routes vacuum to the dash vent air door, etc. Again, when no vacuum is present, all air discharges through the defroster outlets.
Check for a small hose near the firewall that is disconnected, kinked, melted, cut, or otherwise damaged. On a TPI engine, the vacuum source is at the fitting on the right side of the plenum, directly behind the vacuum fitting for the fuel pressure regulator. If you do not find a hose problem, you'll have to remove the control and check for vacuum at the control switch/valve. If a vacuum supply is present, turn the control to different positions to test whether vacuum is ported to the correct line in a given position. If the vacuum just leaks out all around the control, you'll have to disassemble, clean, and regrease the control valve with silicone grease. You could replace the control, but it is likely a dealer-only item that is not in stock. Unless the control is completely broken, I would try the cleaning and regrease. It's worked for me.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
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