Mastertrol mm-2 mini zone-2

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Old 02-21-19, 09:35 AM
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Mastertrol mm-2 mini zone-2

Heat went out with both zones calling, checked the burner and it showed TT open.
Switched main power off waited 30 seconds and back on, it fired and ran until
up to temp, but will not call until power is cycled again. When it is in the state where
the thermostats are calling but the burner is not running, it will run if I jump TT
without cycling power.
This leads me to believe that it is something in the MM-2 controller or the wiring,
I've seen the solid conductor wires break over time.
The MM-2 is mostly relays and I'm tempted to remove it clean the contacts and
reflow the solder connections.
Edit: I see that there are two 24VAC transformers so I should check for voltage.
The dampers are both open with zones calling.

Any other suggestions for debugging this?
 
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Old 02-21-19, 02:28 PM
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Both transformers put out voltage even when it is in the failure mode.

The relays in the MM-2 are socketed so I reseated them keeping them in
the same locations, checked for loose wires. And it remained in the failure
mode, cycled power, still stuck in failure mode. Went to lunch and came
back and it was running.

Not sure of what to look for next.

Edit: it has decided to work normally again.
 

Last edited by Pete2010; 02-21-19 at 05:08 PM.
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