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I have a Reznor UDAP 125 unit heater running on propane

Customer Question
heating my garage. Recently the...
I have a Reznor UDAP 125 unit heater running on propane heating my garage. Recently the heater has begun shutting off before it reaches the thermostat's set temperature. The green light flashes continuously indicating a continued demand for heat and there is a high pitched noise coming from the circuit board when it shuts down. If I shut the power off and wait fifteen minutes the unit will re-fire and run for awhile then do the same thing. What would be causing this?
Submitted: 2 years ago.Category: HVAC
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Answered in 29 minutes by:
1/24/2016
HVAC Technician: airheatman, HVAC Technician replied 2 years ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,024
Experience: Furnace, A/C and heat pump specialist.
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Do you get any other error code when it shuts down prematurely?

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Customer reply replied 2 years ago
green fast flash
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

OK usually if heater is turning off before thermostat is satisfied, a limit or pressure switch is opening but we should get a different code if it does.

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Customer reply replied 2 years ago
That's what I had thought. I'm not sure what I should be doing next.
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

I would start by cleaning flame senser . If that doesn't solve, try to catch it fail and immediately ohm the limits and pressure switch to see which one is open if any

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Customer reply replied 2 years ago
I watched it tonight. It runs along with the green light flashing quickly and the orange light lit for quite some time then the flame just stops. and the orange light goes out as the green light keeps flashing fast. the back fan keeps running but the combustion fan shuts off. If I shut the power off and then attempt to restart the green light continues to flash fast but when I hear the on solenoid click there is a high pitched sound that seems to be coming from the transformer. If I shut it off and allow everything to sit for fifteen minutes or so I can flash it back up for awhile and then it does the same thing again. I think there must be a problem with the transformer overheating.
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

Do you have a meter to see if transformer is bleeding down?

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Customer reply replied 2 years ago
I have a multi meter but I'm not quite sure what I should be checking
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

Transformer should have 4 wires.2 supplying high voltage to transformer and two (going to relays and thermostat) 24 volts. If thermostat is issue, the 24v will drop.

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Customer reply replied 2 years ago
Any idea which colour wires will be carrying which current?
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

Nope.......LOL. Give me a minute to pull the manual and see if it shows me.

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Customer reply replied 2 years ago
Okay I'll check that out
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

Let me know what you find

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Customer reply replied 2 years ago
Will do, Thanks
HVAC Technician: airheatman, HVAC Technician replied 2 years ago

Thanks for letting me work with you to this point

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