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BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22245
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Carrier HVAC LED light is off. No power to thermostat

Customer Question

Carrier HVAC LED light is off. No power to thermostat
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.
hello,
do you have a volt meter so we know for sure where we have power and where we do not?
Customer: replied 1 year ago.
I don't have a volt meter
Customer: replied 1 year ago.
Do I need to go out and buy one? 30 minutes..
Expert:  BillyHvac replied 1 year ago.
no prob...just get cheap one that reads ac volts with 2 leads
Customer: replied 1 year ago.
Hi: I bought a Klein Tools Non Contact tester. Tested against working Carrier and It lights up Bright RED, Test on non working Carrier and it beeps twice red. I assume it detect 12 to 48 volts to AC. I test red wires and Black and White wires. Both get a faint beep of and red light flashes twice
Expert:  BillyHvac replied 1 year ago.
can you back track to the switch on side of furnace and test? The goal now is to work backwards until find full power
Customer: replied 1 year ago.
Ok. So From black power switch I followed all color wires and no signal. I followed black and white wires to silver small silver box connected to main power. There was a faint ping on the volage tester but hard to get. I put the tester on the outside of the small silver box where the main power cable comes in. The voltage is faint. I followed the line and the power picks up as I get farther away from the HVAC and closer to the house.
Expert:  BillyHvac replied 1 year ago.
have you tested the furnace?
Customer: replied 1 year ago.
I was testing the furnace in the attict. Did i say that wrong? Should I be outside at the AC?
Customer: replied 1 year ago.
The thermast has no powerSo I assumed Furnace controlled the power
Customer: replied 1 year ago.
Thermast is 24 volt
Customer: replied 1 year ago.
HVAC LED CODE light is off solid
Expert:  BillyHvac replied 1 year ago.
Ok,
the small silver box..is it a light switch with a round screw in fuse?
Customer: replied 1 year ago.
No switch. I'll send a photo
Expert:  BillyHvac replied 1 year ago.
can you start at the breaker for the furnace and work towards furnace?
May have to remove covers from junction box if necessary
Customer: replied 1 year ago.
Breaker for Furnace? The Board or the Box in the Garage. Attached is what I've tested.
Customer: replied 1 year ago.
Section A with yellow arrow has a faint power signal. Behind that in Section B there is no Power
Expert:  BillyHvac replied 1 year ago.
ok, remove that metal cover and test wire (black) direct
Customer: replied 1 year ago.
I removed the metal cover around secition A. No signal in the black line or white line
Expert:  BillyHvac replied 1 year ago.
thank you
now follow that pipe...go to next point you can check..as you already know you are missing power and we need to find it.
If you know which breaker it is....test there to eliminate a bad breaker
Customer: replied 1 year ago.
Ok. Test whole line from HVAC to Power Junction. Junction Box has good signal. Strange is the Line has a regular then steadily weak signal then disappears the closer you get to HVAC.
Expert:  BillyHvac replied 1 year ago.
ok
just say when you are not comfortable....
but the wires in the junction box in furnace.....we want to unhook the wires that come TO the furnace.
Then use an old extension cord...cut plug end off and wire white to furnace white and black to furnace black...and then plug into a known working outlet...are you up for this?
Of course just in case we want to cut power to the wires we unhook for IF they become live again.
Can you do this cord bypass?
Customer: replied 1 year ago.
Ok, It will take a moment
Customer: replied 1 year ago.
What do I do with the light blue cord in the extension cord? I'm cutting the power and wiring after answer
Expert:  BillyHvac replied 1 year ago.
lt blue not needed..only black and white
Expert:  BillyHvac replied 1 year ago.
how are we doing?
Customer: replied 1 year ago.
I'm getting some power pings on unit but still no RED LED
Expert:  BillyHvac replied 1 year ago.
is blower door pop out switch taped down?
Customer: replied 1 year ago.
I'm holding it with my thumb
Expert:  BillyHvac replied 1 year ago.
Ok,
tape it down.....locate wire that runs from that switch and it goes to circuit board....is there a reading there?.....you may have a power issue that took out the circuit board...
Customer: replied 1 year ago.
Yes there is a faint reading
Expert:  BillyHvac replied 1 year ago.
Thank you.....so even with extension cord plugged into a known working outlet...the board has no light..fuse on board is ok..?
Customer: replied 1 year ago.
Fuse is ok. It was a 5 amp but I changed it to 3 thinking that would help
Customer: replied 1 year ago.
I've change the fuse before and that worked but not this time
Expert:  BillyHvac replied 1 year ago.
it sounds like circuit board is bad...or transformer.
I know this is a pain...but cut power and unhook board and look at back...and smell for a electrical burned smell on board
Customer: replied 1 year ago.
I may call it a day on this one. Lots of cables protruding from the board. What is cost of new board you think?
Expert:  BillyHvac replied 1 year ago.
Around $150......sorry but it sounds like you have a issue AND damage as a result.
I really wish you well
Billy
Customer: replied 1 year ago.
Excellent help. Take care
Expert:  BillyHvac replied 1 year ago.
Have a good weekend..if all set just rate service and I will move from active list

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