HVAC won't switch to Heat/floor vents?
Whoaru99
12-21-2008, 09:53 AM
The HVAC in my (94?) LeSabre generally works good with decent air flow and decent heat. But, usually it won't switch to the floor vent with the heater switch.
If I keep the heater button selected, normally it'll just blow out of the windshield vents, but sometimes after driving for a time (doesn't seem to be any pattern) it'll all of a sudden switch down to the floor vents.
What should I be looking at for a fix...the tootsies get a bit chilly with no floor heat.
If I keep the heater button selected, normally it'll just blow out of the windshield vents, but sometimes after driving for a time (doesn't seem to be any pattern) it'll all of a sudden switch down to the floor vents.
What should I be looking at for a fix...the tootsies get a bit chilly with no floor heat.
Blue Bowtie
12-21-2008, 11:56 AM
Even though the controls may be electronic, the system still used vacuum servos for some functions. Make sure the vacuum supply line at the firewall is intact.
imidazol97
12-21-2008, 07:23 PM
The HVAC in my (94?) LeSabre generally works good with decent air flow and decent heat. But, usually it won't switch to the floor vent with the heater switch.
If I keep the heater button selected, normally it'll just blow out of the windshield vents, but sometimes after driving for a time (doesn't seem to be any pattern) it'll all of a sudden switch down to the floor vents.
What should I be looking at for a fix...the tootsies get a bit chilly with no floor heat.
The poster is right. You may have a broken, cracked, deteriorated rubber hose for the link from the intake manifold to the vacuum storage tank that's on the firewall next to the relay center. It's rectangular. It has a small nozzle sticking out underneath that should have a 1/4 inch rubber tube in it from the intake manifold. Everytime I'd work on plugs I'd pull that tube loose with my arm.
You may have a crack in the vacuum tank that's opening and closing. My guess would be the rubber tube is decayed and rotted and leaking air so sometimes it seals better than others.
Another rubber tube goes from the tank inside the car. The vacuum there is switched between little color tubes that control the vacuum motors.
The dual automatic AC systems had trouble with the plastic connector for the tubes sucking a little rubber layer shut over the vacuum after they aged and softened.
You may have a bad vacuum motor. TAke off the hush panels above the passenger and driver's feet.
You may be able to figure out which vacuum motor is which door inside. There's on that would rotate a door on an axis parallel to the firewall. It also has a vacuum tube connected to the other side so it can be stopped halfway for bilevel airflow. That turns controls the heater and bilevel. Another vacuum line (blue tube on my 98) rotates a door high, on an axis that's parallel to the firewall that shuts off airflow to the defroster and that makes it come out the dash vents for cooling. There's one vacuum that shuts off flow on a spur that goes above the driver's foot; that one's the recirculate door and it's usually closed with no vacuum. It uses vacuum to open the door to pull air that's already in the passenger area. It is slow and has a restrictor pllug in the lline.
I'll see if I find a picture of the vacuum motors. They are replaceable. They have a diaphragm inside and may develop leaks.
You could buy tubing and run a direct line of vacuum from the intake manifold and test each motor if you find you have good vacuum under the hood and into the car normally.
If I keep the heater button selected, normally it'll just blow out of the windshield vents, but sometimes after driving for a time (doesn't seem to be any pattern) it'll all of a sudden switch down to the floor vents.
What should I be looking at for a fix...the tootsies get a bit chilly with no floor heat.
The poster is right. You may have a broken, cracked, deteriorated rubber hose for the link from the intake manifold to the vacuum storage tank that's on the firewall next to the relay center. It's rectangular. It has a small nozzle sticking out underneath that should have a 1/4 inch rubber tube in it from the intake manifold. Everytime I'd work on plugs I'd pull that tube loose with my arm.
You may have a crack in the vacuum tank that's opening and closing. My guess would be the rubber tube is decayed and rotted and leaking air so sometimes it seals better than others.
Another rubber tube goes from the tank inside the car. The vacuum there is switched between little color tubes that control the vacuum motors.
The dual automatic AC systems had trouble with the plastic connector for the tubes sucking a little rubber layer shut over the vacuum after they aged and softened.
You may have a bad vacuum motor. TAke off the hush panels above the passenger and driver's feet.
You may be able to figure out which vacuum motor is which door inside. There's on that would rotate a door on an axis parallel to the firewall. It also has a vacuum tube connected to the other side so it can be stopped halfway for bilevel airflow. That turns controls the heater and bilevel. Another vacuum line (blue tube on my 98) rotates a door high, on an axis that's parallel to the firewall that shuts off airflow to the defroster and that makes it come out the dash vents for cooling. There's one vacuum that shuts off flow on a spur that goes above the driver's foot; that one's the recirculate door and it's usually closed with no vacuum. It uses vacuum to open the door to pull air that's already in the passenger area. It is slow and has a restrictor pllug in the lline.
I'll see if I find a picture of the vacuum motors. They are replaceable. They have a diaphragm inside and may develop leaks.
You could buy tubing and run a direct line of vacuum from the intake manifold and test each motor if you find you have good vacuum under the hood and into the car normally.
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