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I have a UDAP45 it fires up makes one cycle about 90 sec then…

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I have a UDAP45 it...
I have a UDAP45 it fires up makes one cycle about 90 sec then blower fan shuts down and burner fires again gets hot burner shuts off and venter motor runs till it cools coil's then shuts down. I am ready to give up,
any idea's ??
Thanks Tom
Submitted: 3 years ago.Category: HVAC
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Answered in 10 hours by:
6/4/2015
HVAC Technician: Tim H., HVAC Professional replied 3 years ago
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,972
Experience: Experienced in all aspects of HVAC, both residential and commercial.
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Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. Thanks for your business!
Have you tried bypassing thermostat to see if this still occurs?
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Customer reply replied 3 years ago
Hi Tim yes tried to bypass thermostat same thing. Tried all wires the fan motor only makes one cycle? The heater makes two or three. coil gets warm, blower come's on 30sec off , propane on furnace heats "alittle" venter motor runs until cool shuts off.
HVAC Technician: Tim H., HVAC Professional replied 3 years ago
Are you getting any flash code when the unit shuts down?
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Customer reply replied 3 years ago
Yes fast green flash during my 90 sec heat cycle then slow green flash after shut down.
HVAC Technician: Tim H., HVAC Professional replied 3 years ago
And you still have 24 volts across C to W terminals at the board when unit shuts down? If you're not sure, I'd want you to measure this, This is volts "ac" not dc, just FYI.
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Customer reply replied 3 years ago
between G & W1 27.6
HVAC Technician: Tim H., HVAC Professional replied 3 years ago
OK, no not between G and W1 , but right at the unit on the board, I need you to measure between C or common terminal and W with a call for heat. I need to know if, when the unit shuts down, you still have 24 volts between C or common and W.
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Customer reply replied 3 years ago
Ok I will check that I have customers showing up already so will check after closing. Thanks for help so far will get back sat? or when will you be around?
Thanks Tom
HVAC Technician: Tim H., HVAC Professional replied 3 years ago
I have to leave for a bit, too. But I check my questions frequently. And, yes, even on Saturday. So post back as soon as you can. Talk later.
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