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BillyHvac, Journeyman HVAC Tech
Category: HVAC
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Trol-a-Temp damper refuses to close

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Trol-a-Temp damper refuses to close

Can you tell me the number of the Trol a Temp?

Starts with V***
Customer: replied 3 years ago.
Don't know where to find that. The control panel is a MABS-IIL (that's a Roman numeral 2 before the "L"). Does that help?
Yes that helped.

Do you have a voltmeter for a test?

Customer: replied 3 years ago.
Customer: replied 3 years ago.
Also, the M4 and M6 wires on the damper motor are reversed from the wiring diagram in the manual. M4 on the control panel is wired to M6 on the motor, and vice-versa. I had to switch them a couple months ago to get things to function properly for A/C. I neither understood nor liked the fix, but it seemed to help. I'm assuming that is what's messing the system up now, so I tried switching them back just now, but it didn't seem to change anything.

There is also a handy test to check the control itself. Lets do that first to make sure our motor is ok.

See the paragraph labeled "Checkout" HERE

It is quick test just jumping a couple terminals
Customer: replied 3 years ago.
OK - I did a test on the panel and the voltage's were correct on M4 and M6 terminals when I changed the normally open/normally closed switch. Re-connected the wires and ran the tests you linked to. Can't get the motor to move to the closed position no matter what. When I touch the hot wire to M4 or M6 on the motor casing, it stays in the open position or moves back to the open position if I've previously moved it manually.
Thank you.

Just to make sure not seized...did you unhook the linkage?

Customer: replied 3 years ago.
I did not - I just moved it manually. Maybe I shouldn't have?

The damper can bind...and it doesnt take much to stop a 24v motor.

First I would unhook and test the motor...if still no action replace motor.

If it works with damper unhooked and not with it hooked up look for binding in the assembly.

Customer: replied 3 years ago.
Thanks - I'll unhook it and check, but I don't understand how that would make it return to the open position from closed when I connect the hot wire to M6?

Nice catch..

It wont have anything to do with it,

It will be the motor assembly

Customer: replied 3 years ago.
Good news! I still don't understand why it was always going back to the open position, but after disconnecting/reconnecting the actuator, and discovering that the arm was rubbing pretty hard against the side of the damper slot, everything is functioning perfectly. Hooray! Thanks for helping me with this - much appreciated!
That is good news....maybe just binding a bit.

Well done. I am availabe for 30 days afetr rating answer. Thank you!

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