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Blend Door Actuator Test??

I love my Chevy Chevette!
Posts: 4
Joined: 07/11
Posted: 10/28/11 03:50 AM

I am having trouble with the blend door actuator. Can anyone tell me how to test the output voltage to the blend door actuator? And how to test the actuator itself? I need to determine if the dash unit is bad or the actuator is bad. Any help would be appreciated. (this is for an 89 with auto air/heat)  

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I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 10/28/11 08:25 AM

looking at the diagram i got from my friend...

there seem to be 5 wires to the actuator.....

actuator pin numbers

5 and 6 are power wires to move the actuator..   they could be positive or negative according to the diagram depending if the programmer wants the actuator to move.    

5   light green and a black stripe...   goes to the programmer pin C7

6   grey and black stripe...   goes to programmer pin C8

below is the position feed back wiring..

8 is always grounded..  9 is variable voltage feedback to the programmer to tell it where the actuator angle is..  10 is 5 volts reference voltage..

8   black..   Ground for the position feed back sensor only

9   light blue.. goes to programmer D13.  mix valve feedback voltage.. variable between probably half a volt and 4.5 volts depending on the position of the actuator.

10  yellow and a black stripe...    5.0 volts . reference voltage.. comes from programmer C15

i would like you to with the system intact...   turn the key to the ON position..
with your first finger.. hold down the off button on the AC panel.  with another finger... hold down either the temp set warmer button ^ or the Auto warmer button ^  they have an Upward pointing arrow..  

off and warmer on most automatic HVAC systems in GM activate the diagnostics and turn on all the dash lamp segments first..    then one of the displays will start flashing code numbers at you .. write down the entire letters and numbers...

this usually takes me 2 or 3 times to go through to get them all...

post what you get...

did you have the service manual????

electronic versions are available at  or  

since i don't work for the magazine.. i only do this for FUN...  i try to keep my expenses low...  

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