Furnace Blower Not Running: Amana GUCA045BX30

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Old 02-04-16, 05:39 PM
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Furnace Blower Not Running: Amana GUCA045BX30

This is my first post here on doityourself.com
Thanks in advance for your assistance!

Background Data:
Furnace is located in the midwest at an elevation is ~480 ft.
Ambient temperatures fluctuate between 20 F and 60 F when symptom occurs.
House style is Folk Victorian, b.1885.
Furnace Make and Model is an Amana GUCA045BX30 (Gas Forced 90%) installed new about 11 years ago.
Thermostat is a Honeywell Programable, purchased about 11 years ago.

Symptom/Problem:
Furnace switches "on" with thermostat but blower fan doesn't kick in consistently. If it fails to kick on, furnace stays in that mode. Blower can be forced "on" using Fan mode control on thermostat but hot air will not blow.

Steps Taken/Results So Far:
Company who installed system was called. They tested pressure switches (apparently with a manometer) then "exercised" said switches, cleared air tubes of dust, checked air intake and flu for obstruction. System was reassembled and switched on, fan worked... for about 1 month.

I took similar steps to diagnose issue, checked flu where it connects to inducer, checked flu and vents, disassembled connections to pressure switches, checked drain. Reassembled system, fan worked... for about 2 weeks.

Attempted successfully to get fan to work by power cycling system at the thermostat. This worked about 3 times in a row for a period of 1.5-2 weeks. Then I couldn't get results from power cycling in this way. I then repeated the steps of inspecting hoses on the pressure switches, etc. and that again made the fan run.

It's now happening more frequently the need to reset or inspect to make the fan run.

Your Assistance Please

I don't yet have a manometer in my possession but I may get one to diagnose the switch health however I'd love to know what else I should be trying to solve this issue.

Also if I should "just replace the pressure switches" if any one can comment on a reputable source for purchasing OEM switches I'd appreciate it. This model furnace needs a switch that operates at -0.37 iwc.

My local systems dealer/installer said these cost ~$500 for OEM parts but I have found them for ~$45 online.

Thanks everyone for reading!!!!
 
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Old 02-04-16, 08:25 PM
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Welcome to the forums.

You had it serviced a month ago..... why not call them back ?

Keep in mind there are two blowers. You need to use the correct name so that we know which one you are talking about. There is the main blower that circulates the air and there is the draft inducer blower which we just call the inducer.

You said furnace blower not running. If the burner doesn't light the blower will not come on unless you put it in FAN ON. The blower not running isn't the issue... the furnace not lighting is.

Very rarely does a pressure switch go bad. I have never had to change one. People change them left and right only to wind up with the same exact problem.

At this point you don't even know if you have a pressure switch issue. Your furnace is equipped with a diagnostic fault LED. You need to observe the flashing code to determine the problem. The board is usually located in the blower section and there is usually a site glass where you can look thru to see the code. Opening the blower door clears the code.

This should be your manual and at the end it has the diagnostic codes listed.
TechDocs/Amana/Gas Furnace/GUCA-GCCA MANUAL.pdf
 
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Old 02-05-16, 04:27 AM
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Pete,

Thanks for your reply.

The reason I am not calling them back, is they want to replace the pressure switches and charge me 10 times the price of the part or parts (2 switches) and everything I've read so far leads me to believe that the switch isn't the issue. I thought I explained all that in my OP.

It's the blower not the inducer that isn't coming on. Sorry if that wasn't clear in my OP. I listed all the steps the service company and I have taken to diagnose the issue. I am looking for what to look at next. At least since the last time I opened up the furnace to check the hoses, etc.... there are NO fault codes currently flashing, no red light. I have nothing to report there.

Furnace currently works but history as my guide, this is going to happen again soon.

If anyone has any steps they'd recommend I take to diagnose the issue or can advise me on the credibility of a good parts source I would appreciate that. If it comes down to ruling out the pressure switches I don't want to pay the $450 the dealer wants to charge me for them.
 
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Old 02-05-16, 05:29 AM
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Burner ignities but main blower does not start, seems to point to the fact that the pressure switch for the draft inducer motor is OK, check all wiring connections,remove any plug connections and reseat them.
 
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Old 02-05-16, 05:36 AM
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I've disconnected and reconnected the switches electronic connections before, I can do this again. I don't know if that temporarily solved the issue before or not.

Would it be safe to use dielectric grease on the connections to ward off corrosion?
 
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Old 02-05-16, 07:08 AM
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Probably won't hurt to use the grease but it is not the norm to use it.
 
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Old 02-06-16, 06:15 AM
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a gentle bump on this...

Would really like some ideas on trouble shooting this. What would cause an intermittent issue like this?

FWIW... seems to happen more when the system has been idle for longer periods of time, like in the morning after an overnight cool down or late afternoon when the thermostat tries to raise temp after 8 hours of "away".
 
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Old 02-06-16, 11:25 AM
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Without the results of the fault LED..... there will be a lot of guess work.

The companies put the diagnostic function into their boards just for reasons like this.
Even with that LED... intermittent problems can be hard to find.
 
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Old 02-06-16, 02:11 PM
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<< What would cause an intermittent issue like this?
>>



The usual explanation for an intermittent problem is that a part is beginning to fail. Usually the symptom will recur more and more often until it wont operate at all.


<<Symptom/Problem:
Furnace switches "on" with thermostat but blower fan doesn't kick in consistently. If it fails to kick on, furnace stays in that mode. Blower can be forced "on" using Fan mode control on thermostat but hot air will not blow.
>>


Are the burners turning on and staying on?

In general, the circuit board has a timer and energizes the fan motor after a delay to allow the heat exchanger to warm up.

If the fan isn't turning on as you say, either the circuit board is failing to turn on 120 VAC to the blower motor (you need a new circuit board) or the fan motor is energized but not starting up (bad blower motor or perhaps a bad capacitor)

Especially since you can turn the fan motor on manually, it's much more likely that you have a bad circuit board. But check to see if the voltage is being switched on to be sure.
 
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