Air Conditioning/Thermostat Selection

Posted by randallbrink on May 18, 2008, 4:59 pm

> Cycling the system
> Make up a jumper wire one foot long - bare a 1/4 inch at
> each end.
> 1 Bridge R to G Fan should run
> 2 Bridge R to Y cooling should start after timer delay
> 3 Bridge R to W Heating
> 24 V is =A0a =A0low voltage =A0however =A0care should be taken
> R is =A0the =A024V Active which is switched by the =A0Stat to
> Outputs G + Y =A0( Cooling ) =A0G + W ( Heating ) G Fan

> > 1- Check the Wire link R to Ro is inserted
> > 2- Check fan setting switch set to F
> > 3-Put the wire going to G on the thermostat to the R
> > Terminal on the thermostat so the R terminal has
> > two wires R and G ( The fan should run without )
> > wrote in message

> > >I have a puzzling problem. When I select "Cool" on my thermostat, the
> > > central fan does not come on, and so, while the air conditioner
> > > outside runs, it quickly freezes, as there is no air movement. On the
> > > other hand, if I select the heat-cool switch to "Off" and turn the fan=

> > > "On" the fan works fine. But if while the fan is running, I move the
> > > Heat-Cool switch to "Cool" the fan shuts off. I have replace the
> > > thermostat, and have the same problem.
> > > Any help will be greatly appreciated, as the outdoor temperature is
> > > now 90F.

> Will do. =A0Thanks!

P.S. What should I expect to see happen with this procedure? And with
what T'stat switch positions?

Thanks again!

Posted by randallbrink on May 17, 2008, 10:08 pm

> 1- Check the Wire link R to Ro is inserted
> 2- Check fan setting switch set to F
> 3-Put the wire going to G on the thermostat to the R
> =A0 =A0Terminal on =A0the =A0thermostat =A0so the R terminal has
> =A0 =A0 two wires R and G ( The fan should run without )
> =A0 =A0 changing the thermostat switch )"randallbrink" <randallbr...@gmail=
.com> wrote in message

> >I have a puzzling problem. =A0When I select "Cool" on my thermostat, the
> > central fan does not come on, and so, while the air conditioner
> > outside runs, it quickly freezes, as there is no air movement. =A0On the=

> > other hand, if I select the heat-cool switch to "Off" and turn the fan
> > "On" the fan works fine. But if while the fan is running, I move the
> > Heat-Cool switch to "Cool" the fan shuts off. =A0I have replace the
> > thermostat, and have the same problem.
> > Any help will be greatly appreciated, as the outdoor temperature is
> > now 90F.

Mystery continues. I put the "G" wire on the "R" terminal, yes, the
fan did operate without changing the switch position. However, as soon
as I selected "Cool" the A/C came on and the fan in the house stopped
again.

Posted by Telstra on May 18, 2008, 10:26 pm

Cycling the system

Connecting R 24V Active from the transformer to the
G Fan relay Y Compressor relay or W Heating relay
will energise these relays regardless of the thermostat
setting. If this does not occur then R is really Gand G
R. That is the wire to G is really the 24V active and
the wire to R is from the fan relay.
However if it does work correctly then the thermostat
wiring is correct and the fault is in the Indoor Unit
either the transformer or the wiring. My guess is the
wiring, perhaps a loose or burnt wire.
The assumption of course is that the unit worked
correctly when it was installed.

However it appears that the fault is in the indoor unit
wiring

>I have a puzzling problem. When I select "Cool" on my thermostat, the
> central fan does not come on, and so, while the air conditioner
> outside runs, it quickly freezes, as there is no air movement. On the
> other hand, if I select the heat-cool switch to "Off" and turn the fan
> "On" the fan works fine. But if while the fan is running, I move the
> Heat-Cool switch to "Cool" the fan shuts off. I have replace the
> thermostat, and have the same problem.
> Any help will be greatly appreciated, as the outdoor temperature is
> now 90F.
>

Posted by randallbrink on May 19, 2008, 10:25 am

> Cycling the system
> Connecting R 24V Active from the transformer to the
> G Fan relay =A0Y =A0Compressor relay or W Heating relay
> will =A0energise these relays regardless of the thermostat
> setting. If this does not occur then R is really Gand G
> R. That =A0is =A0the =A0wire to G is really the 24V active and
> the wire to R is from the fan relay.
> However if it does work correctly then the thermostat
> wiring =A0is =A0correct =A0and =A0the =A0fault =A0is in the Indoor Unit
> either =A0the =A0transformer =A0or =A0the wiring. My guess is the
> wiring, perhaps =A0a loose or burnt wire.
> The =A0assumption =A0of =A0course =A0is =A0that =A0the =A0unit worked
> correctly when it was installed.
> However it appears that the fault is in the indoor unit
> wiring

Thank you very much for this clarification. I will now carry out this
test and see what happens.

Posted by randallbrink on May 19, 2008, 12:14 pm

OK--when R jumpered to G, A/C unit fan AND indoor central fan
activates. As soon as jumper wire is removed, A/C unit fan stops.
Indoor fan continues operating. (with t'stat switches in "auto" and
"cool".

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Air Conditioning/Thermostat Selection - Page 5