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Posted by tivolo on July 25, 2006, 6:09 pm
Thanks for the reponse.
Ever since the unit was installed there's been a 30 second delay from
when the compressor started to when the blower starts. The same is done
for the heating -- the furnace starts and heats up for 30 seconds
before the blower starts, so I think this is normal operation.
Similarly, the blower usually stays on for 30 seconds or so after the
A/C compressor shuts off.
I've attempted to eliminate the thermostat from the equation by
removing the control portion from the wall so it can no longer send
signals to the furnace. With the themostat removed, I then put a jumper
between the Y and RH posts. Using this technique I can reproduce the
same cycle of events as when the t/stat was on the wall. And, even once
I remove the jumper, the blower continues indefinitely.
I have checked the connections of the t/stat wires to the furnace
circuit board and that all looked fine (which is not to say the circuit
board isn't bad) -- just wanted to eliminate the possibility that a
loose wire was causing the issue.
Thanks again -
Ken
Bob_Loblaw wrote:
>
>
> > * From an off state, I turn on the thermostat to Cool and the
> > compressor starts up. About 20-30 seconds later, the blower on the
> > furnace comes on.
>
>
>
> The furnace blower should come on right away.
>
>
>
> > * Anywhere from 10 to 30 seconds later, the compressor and fan click
> > off and then immediately back on. It repeats this 4 or 5 times, speced
> > anywhere from 5 - 30 seconds apart. After that, the compressor/fan
> > shuts down.
>
>
> The fact that both the compressor and the outdoor fan shut off , plus
> the fact that your furnace fan is acting up, suggests to me that you may
> have either a faulty thermostat, or a faulty circuit board on the
> furnace.
>
>
>
>
>
> > * As soon as the compressor stops, the furnace's blower kicks into
> high
> > gear.
>
>
> It should be on high speed right from the start, unless it's a Coleman,
> which for some reason known only to their engineers and God, the default
> cooling speed used to be medium high.
>
>
> >It is then impossible to stop the blower by means of the
> > thermostat. Turn it off, turn up the temp, turn it to heat, remove it
> > from the wall, ... the blower keeps going.
>
> If, when you remove it from the wall you mean disconnect the wires from
> it, then you have a faulty circuit board, or faulty t/stat wiring.
>
>
>
>
> >To turn it off I have to use
> > the switch in the furnace cabinet.
> >
> > * Now, even though it's off, if I turn the switch in the furnace
> > cabinet back on, the blower comes right back on (compressor/fan still
> > off) and will run indefinitely (as far as I know -- I've let it go for
> > an hour once before shutting it off again).
>
>
>
> Circuit board or t/stat wiring...
>
>
>
>
> > The two techs that came out both diagnosed the problem
> >as the commpressor overamping.
>
>
>
> So why is the outdoor fan shuting down???
> And why is the furnace fan delayed in starting, and running on for hours
> after shut-down?
>
> Furnace circuit board or thermostat wiring.
> Is this a Carrier furnace by any chance, with an HK42 circiut board?
>
>
> --
> Respectfully, Bob
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