Sign In to join the community | Help
Install & Replace

no heat or a/c

 I've replaced the batteries in my thermostat and can here it "clicking" as though it is trying to turn on my furnace or my a/c, depending on where I have the switch turned to. The problem is that nothing happens after, the a/c doesnt turn on even if I turn temp to 68, when its 71 inside, or the gas heater does nothing either even with the temp turned to 80. I checked breakers, what would be my next step, thank you.

Not what you were looking for ? Try posting a question
Posted 2012-12-19T10:43:27+0000  by buckinchute buckinchute

Well I got up this morning and started testing and apparently I'm nit getting any power to my thermostat, according to my DVM. So any help would be appreciated, thanks.

Posted 2012-12-19T18:26:56+0000  by buckinchute

Hey Buckinchute!


I'm following your note that, "I've replaced the batteries in my thermostat and can here it "clicking" as though it is trying to turn on ..."


That clicking sound seems to indicate that the thermostat is functioning.


There are several other options to consider:


1) First, remove and reinstall new batteries following the diagram that shows placement of the + and - end the battery;

2) Flip the switch to "Off" for 30-seconds, switch back to "Heat" and raise the temporary temp setting to test;

3) If this does not work, but you still hear the thermostat click in an attempt to turn on the heater, try this;

4) Have the thin wires on the back of the thermostat been disconnected and/or reattached?;

5) If so, you'll want to locate the manufacturer's wiring diagram online and make certain each colored wire is properly attached;

6) If not, skip this step, but leave temporary setting of the thermostat turned on and go to the heater;

7) Most heaters have three or more safety switches. Inspect each to make certain they are in the "On" position;

8) The first is the "Blower Switch" (which looks like a light switch) usually located on a beam or wall near the heater;

9) Turn it off, wait 20-seconds and turn it back on ... if the heater does not come on in the next two-minutes, proceed;

10) There is usually a float switch if you have a water-catch tray under your heater;

11) The body (top) of this mercury float switch should be level. If not, adjust to level and wait two-minutes. No heat, proceed;

12) Inside the door that covers the igniters and electronics is a compression door switch that must be compressed for the heater to work;

13) Remove the heater door (usually several screws secure the door) and carefully check for cracks in the vacuum hose that connects the gas valve to the vacuum sensor ... the hose is about one-foot long and as round as your little finger. It is typically connected to a silver canister which piggy-backs a small fan motor about the same size as your fist.

14) If the hose appears cracked, cut off the damaged end with scissors and then replace;

15) Slide the door back onto the door track ensuring it activates the door switch and replace the screws;

16) If the heater does not turn on in two-minutes, it is time to install a new thermostat or call a pro.


I know this is a lot of detail for a DIYer to follow ... you might want to print these steps and keep them with you as you proceed. Once you've followed this list, you'll be able to diagnose most of the simple reasons HVAC units do not work.


NOTE: Just two days ago, I found that one of my tenants had installed new batteries backwards. I often find the vacuum hose ends cracked to the point that the vacuum switch will not operate. And then there is that pesky float switch ... if someone is moving boxes or other items in and out of the area near the heater, it is very common that they step on or kick this switch ... effectively disabling your heater.


FINALLY: Thermostats operate on very low voltage ... it is fairly common for people to misread a volt meter or get no reading at all.


So, #1-If the batteries are installed correctly, #2-you hear a click when the thermostat tries to send a signal to the heater, and #3-the micro-wires on the back of the thermostat are connected properly, #4-then the problem will likely be at the heater itself.


Follow these basic diagnostic steps, and rely upon what you hear and see more than what a volt meter tells you.


If your heater is not operating after checking both the thermostat-side and the heater-side, you can still DIY using a new thermostat. The Home Depot has a great selection, including WiFi-Enabled Programmable Thermostats you can operate with your iPhone or from any computer terminal.

WiFi-Enabled Programmable Thermostat.jpg

If you've had enough, call a pro!

Posted 2012-12-20T17:29:52+0000  by Pat_HD_ATL
Not what you were looking for ? Try posting a question