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rkpatt 07-28-2008 02:17 PM

A/C won't turn off with thermostat temp adjustment ( Goodman system )
Furnace is a Goodman GMP-075-3 1998
A/C condensing unit is a Goodman 2 ton 10 SEER unit 1998

It is now the middle of a hot summer . The split system is cooling fine but a problem has just developed where the A/C and fan stays on regardless of the thermostat setting . I can only tun it off by placing the switch on thermostat in the off position (between heat and cool ) . I suspect that is probably a bad control board or thermostat . How do i diagnose this further (and repair) ? - Thanks

8 Ball 07-28-2008 06:46 PM

Take the wire off the Y terminal at the stat, and tape it off. If the AC stays off, its probably the thermostat. If the AC continues to run, its probably the board.

Thermostats are easy to change, just mark your wires and reconnect to a new stat. Boards arent that much more difficult, again mark your wires and reconnect.

rkpatt 07-29-2008 08:08 AM

The problem was the thermostat -

Before I received your reply , I substitute the thermostat with one from another system in my house . Since it was the same make and moder, I didn't have to remove the base plate and connect and wires . It worked fine . I will replace both thermostats with Honeywell digital thermostats .

BTW - Someone else told me about disconnecting the green thermostat wire at the control board (then repower and hold door switch down -on ) . If everything kept running then it was the board . Would that also be a correct diagnostic procedure for this type of problem too ( or what other kind of problem ) ?


8 Ball 07-29-2008 05:58 PM

The green wire is normaly the fan, Y energizes the fan and the condensing unit. If you had fan problems...maybe.

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