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No heat. Help! Replaced batteries on thermostat. Turned up…

Customer Question
Hello. No heat...

Hello. No heat. Help!

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

Replaced batteries on thermostat. Turned up to 90. It is on heat and the fan is on auto.

Contractor's Assistant: Do you plan on doing the work yourself?

Yes

Contractor's Assistant: Anything else we should know to help you best?

At the furnace.

Submitted: 6 months ago.Category: HVAC
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Answered in 5 minutes by:
12/31/2017
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago
HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 18,706
Experience: 20yrs in the HVAC industry with certificates and degrees.
Verified

One moment please..Note it takes time to type and add links so please be patient. Also the site will send you a phone call offer, that is not me.

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HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

Can you get to the furnace and check the control board to see if you have any error codes flashing on it?

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Customer reply replied 6 months ago
No flashing
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

OK can you get to the thermostat wires?

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Customer reply replied 6 months ago
You want me to check voltagem
Customer reply replied 6 months ago
Voltage?
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

No I want you to take the Red wire off the R terminal and the White wire off the W terminal and put them together and see if the furnace comes on.

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Customer reply replied 6 months ago
Did I lose you?
Customer reply replied 6 months ago
Ok one sec
Customer reply replied 6 months ago
Touched them together. Nothing
Customer reply replied 6 months ago
You there?
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

Get to the furnace board and see if the fuse on the board is blown or make sure you have power to the furnace. Note there is a delay in responses please do not post until you get one from me. Thanks

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Customer reply replied 6 months ago
5 amp fuse looks good. Tested with meter. Has continuity.
Customer reply replied 6 months ago
Should I put the red and white wires back into place?
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

You can also confirm you have 24 volts across R to C at the board

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Customer reply replied 6 months ago
Just a side note. The flame rollout switch has been jumpered. When I remove the jumper the flu motor starts right up along with the blower motor.
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

So it was jumpered previously?

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Customer reply replied 6 months ago
Just replaced the jumper. Both blower stay on now.
Customer reply replied 6 months ago
No flame. No clicking for the ignitor. Wiuld be very hsrd to hear with all of these blowers going.
HVAC Technician: HVAC Guru, HVAC TECH replied 6 months ago

Let me see if another tech can help, I am not sure what unit you have.

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Customer reply replied 6 months ago
Blower motor went off. Induction motor is still on.
Customer reply replied 6 months ago
What? Just gonna dump me? I can tell you the model.
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 9,701
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Verified

Hello, I am another technician, the odds are in the 90%+ range that the printed circuit board is bad..

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Customer reply replied 6 months ago
Wher can I get one on New Years Eve??
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

After the furnace sits for 10 minutes with the burners and blower off, use a hair drier to warm up the printed circuit board that is mounted on the blower to 130F or so. then try the furnace again, if the main blower does not come on then the board is bad, it has microscopic cracks in it.

You will have to order one online Monday or tuesday, http://www.shortyshvac.com OR call in a local technician who might be able to buy one from his local wholesaler.

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HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

Meantime you can try setting the thermostats *fan switch, to FAN ON... that has a good chance of working

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Customer reply replied 6 months ago
I can get the main blower to come on. Just no ignition or flame.
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

We can also try hot wiring the blower motor directly to a 120 volt power source, that takes some time and some skill. If you want to try that

Take close up, exceedingly well focused photo's of the wiring diagram glued inside the furnace/air handler door, and the printed circuit board mounted on the blower, , that shows where the thermostat wires connect, and I will mark them up with trouble shooting instructions.

Use the 'add files' link next to your send button to get the photo(s) to me.

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Customer reply replied 6 months ago
When I remove the jumper from the flame rollout switch the main blower come right on.
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

.

In that case it could also be a bad ignitor, locate the two igniter connection points on the printed circuit board, and measure for 120vac there, in a time frame between inducer fan running and the time it stops... if you get 120v and the igniter is not glowing, then its a bad igniter... same story on availability.

When you remove jumper from the flame roll out switch you simulated an open switch, that tells the board that the furnace is over heating and turns on the blower. that does not change our diagnosis so far

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Customer reply replied 6 months ago
Should I leave the flame rollout jumper on or off? Is the normal state open or closed. I'm assuming closed because it has likely bern on here for years working fine.
Customer reply replied 6 months ago
3 wires come from the ignitor/flame sensor and plug into the gas valve. They do not go directly to the cicuit board.
Customer reply replied 6 months ago
Can I light it manually?
Customer reply replied 6 months ago
If I heat up the flame sensor.......will the gas valve open to light the burner?
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

click here please, disconnect the heat and cool motor wires as shown by yellow x's then run the heat wire to the blower door switch.

Heating the flame sensor changes nothing, it does not sense heat it senses the actual flame, that changes is 24vAC input to DC and the board senses that change

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HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

reconnect the flame roll out switch... is normally closed

If we to too many things at once. we will get all messed up

Earlier you said the burners lit, so we know the ignition is OK

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HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

When you get the blower running its time to rate my work for the day, that is how the company pays me. Locate the 'Finish and rate your expert' link near the top of your page and click on it.... I will hold the question open to for any follow up needed later when you post back to this thread.

Thanks

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