--24.99.xx.xx

Did you look inside the covers? Have you tried to google? I use my phone to take pictures of the old one before removing, and also label prior to removal. Could you do that? --173.74.x.xx

I googled and could not find. Also, I made a mistake of not noting down the previous wiring colors. I went by my memory and cannot figure out the three wires that are lose and hanging...... ooops. --24.99.xx.xx

Plus, where do your wires go too? Is their an abbrevation or code on the hook up? --67.236.xxx.xxx

--98.112.xxx.xxx

There are 5 Terminals named G, COM24V, W, Y and R. I see the wires as Green, White and Red. But which wire would go to COM24V and Y, is the question. --24.99.xx.xx

When one removes any sort of a circuit board one is better to make a wiring diagram or use a digital camera so installing the wires is done correctly. There may be wiring diagram on one of panels of furnace or inside the furnace. If one has voltmeter then measure which wires have voltage. If one install wires incorrectly then one may damage the circuit board or the transformer. Usually red and white will have 24 Vac which can be verified with voltmeter. Green is usually ground which can checked with ohmeter as one can check when grounding to the furnace. --74.220.xxx.xx

Com24 is the 24 volt ground wire, the other leg of the R wire. Look on your thermostat for the C terminal, it will be the same wire. Y is the typically yellow wire that goes to the a/c contactor. You don't need it if you have heat only. --216.218.xxx.xxx

To add what gevans said, ignore the Com24 (B), and the Y, the Y is to trigger the central air unit outdoors along with the house fan like the G does and the Com24 is used to supply voltage to extend battery life in the digital t-stat. --76.241.xxx.xx