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Re: to which (two ) terminals on the furnace PC board
Hi, at the PC board, you will connect the red to the R terminal, and yellow if that's the color they used to the Y terminal which may have a wire from the stat on it already. This will close the contacts on the contactor on a call from the thermostat for cooling. Please be kind when rating me as I know you will. Thank you. Sincerely, Shastalaker7 A/C, Heating, & Refrigeration Contractor PS, if you run the wires and connect to R and C for common, the outdoor condenser will run all of the time on its own. It will have 24 volts straight to it constantly.
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Bad/ stuck fan relay or temerature sensor is not shutting the fan off. Or there is a short on the low voltage fan control circuit. Check to see if the Green terminal is jumpered to the Red terminal at either the furnace control board of the 'stat, if not, ohm the wires with both ends off- I've seen installers accidently shoot a staple thru the wire and short the wires together more often than even I can believe! Hope this Helps! PS Some furnaces have fan switches inside the furnace- check for one and see if it's "on"- sounds too simple, but sometimes the "simplest" is the correct answer.
Check the 3-5 amp fuse on the control board, if the fuse is bad then there is a short somewhere in the low voltage circuit, usually in the thermostat wires. If the fuse is good check for 24 volts atbthe R and C terminal, if no voltage there then the board is bad and must be replaced.
The control voltage comes straight from the furnace or thermostat. Its 2 to 5 wires depending on if you have a heat pump or conventional system. If you have a control board on the inside of the furnace that has the terminal (y), then your control voltage will come from that terminal and the common terminal. Sometimes they have it connected to the (y) terminal from the thermostat, but will usually still be hooked up inside or right by the furnace. In (COOL) mode, the thermostat energizes the y and g terminals, (cooling and fan), which is sent to the outside unit on the contactor. You need 24v going to the contactor outside for it to pull in and make contact. If you have lost the low voltage, then it usually means bad transformer on the furnace (which nothing would work), faulty control board on furnace, faulty thermostat, or your low voltage wires could of been cut, chewed through, etc. If you do have the low voltage by chance, then it could be a faulty contactor on the condensing unit. I'm just throwing some things out there, its kind of difficult without knowing all the equipment you have. Have anymore questions, just ask. Good luck!
You need to get low voltage wire known as 5 wire. run wires thru wall to stat and furnace Red wire goes to R terminal white to W terminal Green to G terminal Yellow to Y terminal on both the stat and furnace circuit board. Now you need a wire called 2 wire low voltage wire run that from furnace circuit board to outside A/C. At furnace hook red wire to Y terminal and white to C terminal doesnt matter which ones you hook up at outside unit. Do it just like i told you this will work properly.
If this helps please rate me.
Go to the low voltage terminal board in your furnace. Follow the thermostat wires ti find it. Set your meter above 30 volt A/C. Hook one lead to one side of the transformer. Touch the other to the RED wire on the terminal strip. If you don't read 24 volts, switch terminals on the transformer and touch the red wire again. If OK then touch your lead to the YELLOW wire or the terminal marked Y on the terminal strip with the thermostat set to cool. you should have 24 volt now between the lead on the transformer and the one on the Y terminal. Go to the condensing unit outside and test the 2 18 gauge wires there. the 2 readings should be the same. If you have any trouble with anything, please write me back. Roger
Try the fan switch inthe ON setting rather than the AUTO setting, if it runs, power, both low(24) and high(115 or 230) are present. if not, check breakers and fused outlet if a split system furnace, read for 24 volts at red and common on low voltage terminal board where thermostat wires go on the furnace, if no 24 volts there and poers entering furnace, transformers bad.
some one has the humidifier hooked up to the R and W on the furnace.
1. it should be hooked up to its own transformer or to a proper low voltage terminal on the circuit board(beware there are high voltage HUM terminals) markd HUM and the other wire to C or the common.
2. You could hook the wire to W or white and C Common but I would rather see a seperate transformer since there is a possiblity this could cause solenoid chattering
White wires are commonly the common connection (sorry for the pun). L2 is also considered the common leg. You did not mention if you are looking for high voltage or low voltage common. L2 is your high voltage leg. If the power venter ties into the thermostat circuit, W on the circuit board is the common terminal.
I just solved a problem with mine today. One of my low voltage power wires to the humidity control had a bad connection. I reconnected it and I could again hear the solenoid valve clicking as I adjusted the dial control.
I found the problem with a voltmeter: there was voltage at the power terminals on the humidity control terminal board, but there was no voltage at the solenoid valve terminals. It was hard to push my big wires into the terminal board, but I finally secured the connection!