Mechanics

BLEND DOOR CYCLES WHEN ON HEAT SETTING

1998 Ford Taurus

Air Conditioning problem
1998 Ford Taurus 6 cyl Two Wheel Drive Automatic 110000 miles

If Temp setting is in the middle or on COLD there is no problem. When the temp control is moved past center to HEAT side the blend door begins to cycle open and closed between cool air and heat. You can feel the temp change so I know that bend door and acuator are working but not properly stopping at the right heat setting. What would cause the cycling of the blend door when temp is set to heat? This does not happen on cool side of temp guage, only heat side!
Avatar
Zue
January 12, 2010.



Its not the blend door issue
I would suspect a clogged heater core (very common )
start and warm the engine
open hood and check heater hoses by the firewall
both should be hot
if both hot and no heat on the inside its a blend door issue
if one hot and one cool or warm
heater core need to be flushed
disconnect hoses from engine side
plug the bypass hose and flush heater core

BMRFIXIT
Jan 13, 2010.
WHAT! Do you copy paste this on every heater question. Did you not ready my input about the cycling of the blend door that is clearly audiable? I have read this answer on countless heater questions and frankly it is not always the answer. Can you not realize that the blend door action has nothing to do with the temp of the heater core (or does it)?

Tiny
Zue
Jan 13, 2010.
OOO I did see what you wrote
and YES I do copy and Paste
What else you need to know

lets go back to the NO heat
if you elect to do what I Copied and pasted you would find the problem

we do about 3 to 4 Taurus and sable a week with no heat
Again and only if you elect to do so
open hood and check the two heater hoses
both hot its a blend door and or actuator
if one hot one warm or cold
Heater core need to be flushed

BMRFIXIT
Jan 13, 2010.
How does that explain the actuator door cycling back and fourth, The lack of heat is becuase the door will not stay in the heat position as it goes back and fourth. As it opens to the heat side you can feel heat for a breif period and then the door moves to the cold position again. Back and fourth it goes.

Are you telling me that flushing the core will cause the electrically controlled actuator and door to begin behaving properly? If so explain how the electric actuiator is affected by a core that may be blocked or restricted. I am very curious how that is.

Tiny
Zue
Jan 13, 2010.
OK, I have resolved the problem on my own and for the readers of this post I will supply the answer I discovered. First off it was the Blend Door Actuator that failed and not the Blend Door (or any other solution provided by the expert).

The blend door was cycling on and off because the Actuator gears were stripped out and the motor was trying to move door up but was slipping back to cold status each time causing the Acutator to continuiously try and move door up to Heat position. Replacing the Actuator solved the issue.

About replaceing the Blend Door Acutator. It was not as difficult as many make it out to be. I did not need to remove much to get to it. I removed the glove bow by removeing 3 (7mm) screws under box and the wire/string that limits the downward movement. I also backed out the radio assembly to gain access. 5 x 8mm screws hold the actuator and sheild in place. An 8mm socket and a 1/4 drive ratchet worked perfectly to remove actuator. Total time to R&R was about 1 hour. Actuator from O'Reilly's and Autozone was 49.00 USD. Alow a couple of days for ordering part (was not on the shelf).

Heater working great again.

Tiny
Zue
Dec 5, 2010.