How to tell if electricty is getting to the themostact in house. no heat or air come on, like no electricty

Question

the heat and air in my house stop working, like no electricty is getting to the themostact, i have a breaker box and have flip all the switches but do not no if the electricty is getting to the themostact

Answer 1

Go to your local hardware store and pick up an electrical tester. (They are only a few bucks) It has two wires (red and black) and a light. Take off the thermostat, and touch the metal tips from the tester to the electrical wires at the thermostat. If the tester lights up, you have power and the problem is elsewhere. I hope this helps you!

Answer 2

If it has standard color coded wiring touching the red wire to the green should turn on the fan in the air handler or furnace.

If it doesn't do anything you may not have power to the indoor unit (furnace or air handler) or the transformer or fuse is faulty in the unit.

You would have 24 volts a/c between the red wire and any of the other one.

If something blew a fuse or the transformer is out you have a short somewhere and needs to be found and corrected.

Check for the obvious like a tripped breaker.

If you have an air handler inside it will be a double or 220 breaker and a furnace will have one 115 breaker.

Answer 3

is this a heat pump  or gas fired unit    try a  meter from red  (power) to  green (fan) or blue (common)  or yellow (cool )    you need 24 volts if youd do not have 24 volts  two things may be wrong    (1)  bad transformer   or   the door on the furnace may not be tight enough to trip the safty switch ?      BE CAREFUL THIS CAN BITE YOU       (35 years in the field of a/c )

Answer 4

Remove the thermostat cover,turn the thermostat down then up and watch for a arc when the points break,if there is an arc you have power to the thermostat.if not,no power.

Answer 5

This is why god makes AC repairmen.  Several things could have happened.  First, your unit may be bad.  You may have a tripped breaker.  

Answer 6

do you have a swtich on the drain line that will shut the a/c down if the condesate line backs up, you can put your ear on the air handler and if the low volt trans former is working you will hear a hum. vac the line from outside if it has a switch. All these people who tell you to get a meter are nutz, if you had a meter and the knowledge you would not be here. You could have up to three different power ranges, 120v, 220v, 24v. Check simple things first then call somebody who knows so you do not get hurt. Use a meter set on OHMS to check voltage and you will see a blue flash and the will be junk fast.

Answer 7

  Flipping the switches in the breaker box doesn't prove anything when it comes to heating and air conditioning systems, as they mostly work off of a low voltage transformer.  Maybe 12v or 24 volt.

  Many of the transformers are in the furnace, and you need a voltmeter to check output voltage on these critters.

  If you're not familiar with electrical circuits, it's best to call a service man.

  If you had some experience with electric, the schematic should be posted somewhere on th efurnace, or with the installation papers.

  Check the line voltage first, (120v) and if ok then check the secondary voltage  if none then the transformer is bad.

Answer 8

Pull the two wires-they are low voltage-skinny- and touch them very briefly,spark no spark? See transformer on furnace, breaker,,maybe new thermostat if sparking.  

Answer 9

You need a voltage meter to check. these units usually have low voltage so set at a lower range to test. You can get a cheap one from harbor freight or radio shack.

Answer 10

As mentioned , voltage testers are inexpensive.

Might check the furnace to see if you can find the low voltage transformer that the T stat wires run to.

If there is 110V on the primary side, the furnace has power & if there is none  on the secondary ( low voltage side) , the transformer is bad & the T stat cannot tell the furnace to turn on.

If low voltage is present , check the connections on both ends of the thermostat wire.

The transformers are cheap & easy to replace( w/ mains furnace bkr off.)

Does not happen often , but it does.

Think a new transformer was about $6 & a cheap meter might be  $15.

Best regards