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Troubleshooting Damper Motors & Control Panel

8247 Views 2 Replies 2 Participants Last post by  ARB
Hey guys, was hoping you can help me with some troubleshooting! Sorry in advance for the long post; I just want to make sure I provide all relevant information...

To start with some basics, my house has an oil furnace with forced hot air, two zones (upstairs and downstairs), and in each zone I have two dampers that operate in tandem. The damper motors are Trol-A-Temp MSTN and the control panel is a Trol-A-Temp Mastertrol Mini-Zone model MM-2. My current problem is that all four damper motors stay open all the time.

Let me also provide a little more history that may or may not be relevant: Last year, I was having the same problem, except it was only the upstairs dampers that were staying open. Attempting to troubleshoot the problem and not knowing how to do it the proper way, I swapped the two upstairs motors with the two downstairs motors to see if the problem moved downstairs. Indeed it did, so I assumed that the two motors (now downstairs) must be bad. I never did get around to replacing them. But now, as I mentioned earlier, all four are not operating. Seems like too much of a coincidence that all four motors would fail at around the same time, and that they would fail in pairs, so I figured I better troubleshoot this in the proper way. ;)

So, some of the questions that come to mind are:

-- Do these symptoms suggest a specific problem?

-- Does anyone know how to troubleshoot the control panel?

-- I have some documentation on the damper motors, which contains a troubleshooting guide. In this guide, I need to apply 24 Vac to a couple of the terminals. I suspect this is a dumb question, but where do I get the 24 Vac from? (Is there a source I can tap into to get this?)

Thank you for any and all suggestions! :thumbsup:
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I'm not familiar with your control panel but, I'm guessing there is a terminal strip on the panel with wires to the zone dampers. Check for 24 volts across each pair of wires at terminal strip..If you have 24v across any pair then check to see if 24v at each damper motor. If there is then chances are that motors are defective. BTW you could buy a 110/24 volt furnace transformer and use extension cord to power the 110 and run secondary 24 volts to each motor to test. I'm assuming the dampers are normally open without voltage and close when voltage applied. Make sure you tape the 110 v terminals before you plug into receptacle. Also disconnect wires at motors to prevent feedback to control terminals. You should be able to get a digital multi meter for $40..sometimes on sale for around $10.
Techpappy - Thanks for your reply... I'll take another look at the panel and see if I can make sense of it. Thanks also for the suggestion to pick up a furnace transformer. I'll let you know how I make out...
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