Ask Experts Questions for FREE Help !
Ask

    FAN doesn't work when it's 'Auto', but works fine at 'On' in my central air/furnace

    Asked Jun 14, 2005, 02:20 PM 1 Answer
    undefinedFAN 'On' or 'Auto'FAN 'On' or 'Auto'
    Hi,
    I have programmable thermostat connecting air condition / furnace system. Now if I turn system to 'Cool' and Fan at 'Auto', no cool air come out (compressor works, you can hear the noise). If I set FAN to 'On', life is getting better. But the FAN will runs forever even the compressor stops.
    Please help to point me to the right dircetion.


    Thanks

    Last edited by Billx; Jun 14, 2005 at 02:21 PM. Reason: find some typo
    Search this Thread
    Share |
    1 Answer
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member
     
    #2

    Jun 14, 2005, 08:08 PM
    Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

    With the thermostat calling for cooling, check to see if the ''Y'' terminal at the furnace is hot. The fan on position bypasses some of the internal wiring of the furnace. You need to trace the circuit from the ''Y'' terminal at the furnace to the blower. There may be a limit switch or timer, plus a relay. If you are lucky, there will be a schematic inside the furnace. If you need to, post back with what you find.
    Helpful

Not your question? Ask your question View similar questions

 

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Add your answer here.


Check out some similar questions!

Furnace blower can not auto start [ 29 Answers ]

I have a problem with my furnace blower not starting automatically. It works good when I swiched the fan option to "ON", the furnace was burning and fan was running. However if I pick "AUTO", only the furnace burns periodicaly, and the fan totall gets stuck. I am wondering if it is a wiring...

Furnace Manual Fan OK - Not Auto Though [ 1 Answers ]

I have a York Stellar Plus (15yrs old) with an Auto and Manual Fan Switch on the T-stat. The Fan will work when turned to ON (at the T-Stat) but it will not come on when you turn the heat on with the Fan switch turned to Auto. I have replaced the Limit Switch. No difference Thanks!

Central Air works intermittently [ 6 Answers ]

We have relatively new house. The central air was installed in 2001/2002. This is OUR first time using it. First thing I realized was the circuit breaker for the condenser and fan was bad, so I replaced that. The unit ran fine for a few days. Then we shut it off for a few days. When we...

Auto sprinkler - works yesterday, not today? [ 1 Answers ]

:confused: I finally programmed my sprinkler system correctly and it worked yesterday afternoon - went through all six zones with no problem. This morning it did not start. The controller was going through the zones, but the pump never started. We had wasps move into our pump start relay last...

Furnace won't heat in Auto [ 2 Answers ]

I have read the different posting and replys, but they don't seem to address my problem. Friend has an older Kenmore Power Miser 70 that has an old electronic ign. (no flame senser). The furnace will heat when the fan switch is set to "on" position, and it will cycle the heat. When the fan is...


View more questions Search