Heater problem?

1991 GMC C1500
250,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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ALAN RAY
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Instead of one indicator arrow, it flashes all arrows. The blower motor works fine. 1 year old thermostat, radiator and reserve full. Not sure if the problem is in the heat) air control module (OEM board) or one of my three actuators?
And how can I tell where and which is the problem?
Oct 19, 2022 at 7:26 AM
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JACOBANDNICKOLAS
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Hi Alan,

Are you able to control any of the functions? Also, the controller head had issues years ago. I remember a service bulletin where it would lock up causing the actuators to continue getting power and start clicking. The only fix was to replace the controller head.

Let me know if you have any control and exactly what is happening in addition to the lights flashing. Also, 16149268 is the original equipment part number. See pic 1 below for confirmation.

Take care,

Joe

See pic below.
Image (Click to enlarge)
Attached Media
Oct 19, 2022 at 6:49 PM
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ALAN RAY
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Thank you, Joe. I do not hear any clicking in the actuators. Cannot control anything on the operating heat/air display panel.
By controller head, do you mean the OEM board/module?
Oct 20, 2022 at 4:23 AM
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JACOBANDNICKOLAS
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Hi,

It's the control unit I attached a pic of above. If you can't control the temperature or the airflow direction, that is what it sounds like has failed. Also, I found a newer part number,16143956.

Let me know.

Joe
Oct 20, 2022 at 6:23 PM
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ALAN RAY
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Thank you sir.
Oct 21, 2022 at 2:55 AM
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JACOBANDNICKOLAS
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Allan,

You are very welcome. If you have a chance, let me know how things turn out for you. Also, please let me know if there is anything I can do to help.

Take care,

Joe
Oct 21, 2022 at 8:29 PM
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ALAN RAY
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Got it working. It was the module board. My son, a Spartan school graduate and good with this type of stuff, cleaned and re-soldered a bunch of suspect areas. Blowing hot, just in time for winter.
Thanks Amigo.
Who knows, you may not have seen the last of me.
Oct 25, 2022 at 4:45 PM
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JACOBANDNICKOLAS
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Hi,

I'm glad to know you got it taken care of. Also, please feel free to come back anytime in the future. You are always welcome.

Take care,

Joe
Oct 25, 2022 at 6:28 PM