heater working and air conditioner is not working on auto

gym730

I am having a problem with my central air unit blower it is a older bryant model sl-f at least 20 years old the heater works great on auto but my air works sometimes on auto it works great on manual . I was thinking its my relay can anyone help me. I have replaced the contactor and the thermstat

clocert

Give us a little more details. what do you mean sometime auto, great on manual.

gym730

It works in the manual mode no problems but in auto it works sometimes and sometimes it doesnt when it doesnt work in auto it freezes up right now it is working fine

clocert

What kind of T-stat you have, Central air uses temp setting to turn it on or off always. How do you turn it on manually? let us know how you set your T-stat to turn it on or off (auto and manu).

gym730

I have a programable thermostat WhiteRodgers it has the fan switch witch i can turn to on or automatic and it has a system switch heat or cool

Doc Holliday

It sounds like a stat problem. You can check by removing the cover plate of the stat, exposing the wiring. First turn power off to the furnace by way of breaker. At the stat jump Y to R to bring on cool. Flip the breaker back on to the furnace. If a/c comes on each time you flip the breaker off and then on then it's the stat.

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Thanks.

clocert

OK, I understand. The (manual) fan on switch only turns on the blower fan, not your A/C. In order to turn on your A/C, you have to set the temp lower then your room temp. Your A/C will stop once the room temp reach the set temp. It is automatic on and off. May be that is why you think it only works sometime. That is the way A/C works. when room temp higher then the set temp, it will be on, when room temp reachs the set temp, it will be off. Wait, Are you saying you have to use fan on switch to turn the A/C on even the set temp is lower the room temp ??

gym730

But why would it only run on auto sometimes and not all the time? Just to let u know the thermo is brand new The outside unit is working fine its the blower that isnt working in auto somtimes

clocert

I see your problem now. the blower does not work in auto mode, but you can turn it on by using 'fen on' switch. I'll check the T-stat to make sure it is wired correctly, the next thing will be the control board. you need to use multi-meter to check if ,under Auto mode, you have power at the blower terminals.

gym730

I might of found my problem there was a loose wire connector from the thermo . If that's not it i will be back on here Thank you for your help

Tindra

Jumper are to G at the unit. (do not forget to make sure door switch is closed, use tape) If the fan runs go to the thermostat jumper are to G. If the fan runs from the board and not the t-stat you have a bad wire connection from t-stat to unit. If the fan does not run from jumping are to G at the board it may be a bad board or relay let us know.