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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7776
Experience:  Furnace, A/C and heat pump specialist.
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I have a Reznor UDAP 125 unit heater running on propane

Customer Question

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: 10 months ago.
Category: HVAC
Expert:  airheatman replied 10 months ago.

Do you get any other error code when it shuts down prematurely?

Expert:  airheatman replied 10 months ago.

See below

Customer: replied 10 months ago.
green fast flash
Expert:  airheatman replied 10 months 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.

Customer: replied 10 months ago.
That's what I had thought. I'm not sure what I should be doing next.
Expert:  airheatman replied 10 months 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

Customer: replied 10 months 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.
Expert:  airheatman replied 10 months ago.

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

Customer: replied 10 months ago.
I have a multi meter but I'm not quite sure what I should be checking
Expert:  airheatman replied 10 months 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.

Customer: replied 10 months ago.
Any idea which colour wires will be carrying which current?
Expert:  airheatman replied 10 months ago.

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

Expert:  airheatman replied 10 months ago.

Looks like red and brown going to SEC and COM terminals on board

Customer: replied 10 months ago.
Okay I'll check that out
Expert:  airheatman replied 10 months ago.

Let me know what you find

Customer: replied 10 months ago.
Will do, Thanks
Expert:  airheatman replied 10 months ago.

Thanks for letting me work with you to this point

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