Heater control

[40buickcoupe]

Has anyone experienced any problems with there heater control. Sometimes my heater blows cool air when it is set on heat. If I take the heat selector and go from cold to heat a few times the blower will start to blow hot air. Any help would be great.

[rixGAphx]

Try a 'search' on this forum for 'no heat'.

The most common reason for an HVAC control problem is a faulty vacuum system (the little dampers in the ductwork are powered/controlled by engine vacuum).
There's a tube from the intake manifold to the vac reservoir (black plastic grapefruit under the battery) and thence to the HVAC control panel on the dash.
The control panel distributes 'vac signal' to the individual dampers.

I owuld check that whole system for loose connections, cracked tubing, and other possible leaks .

Good luck,
-Rick

[40buickcoupe]

That vacume just controls what vents will open does that control hot to cold also?

[coupe]

2.3 in a 99?

[rixGAphx]

That vacuum just controls what vents will open.
Does that control hot to cold also?On 'older cars', the vacuum controlled a 'modulating valve' that opened/closed the flow of hot coolant thru the heater core.
On even OLDER cars, instead of vacuum control, the modulating valve was operated by a lever and cable, kinda like a lwan mower throttle.

On the GA, the hot coolant is ALWAYS flowing thru the heater core.
The difference between hot air being produced or not, is whether the fanbox is sucking in cold outside air, warm inside air that's being recirculated, or a combination of the two.
It's a 'blend-door' that also controls the way air flows thru the AC evaporator of cooling/dehumidifying.
All of this blending is vacuum-controlled, so that system must work perfectly.

So in addition to directing air to various vents (floor, dash, or windshield), the vac also diercts where the air will be sucked FROM (passenger floor, or outside, or both), and how the air moves around inside the ductwork for hot and cold balance.

Hope this helps,
-Rick

[40buickcoupe]

Thanks Rick, I will check out the vacumn system