AC question, what's the circuit board in the compressor cabinet?

Perhaps it's a timer to prevent short-cycling.

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mm writes:


Nope.  About $20 on grainger.com.

Your description sounds like you have a short-cycle delay timer.  You can
bypass it to diagnose that component vs the contactor.

On Sun, 17 Sep 2006 20:22:42 -0500, Richard J Kinch


Wow.  I thought 130 was a lot.

To give myself a pat on the back, I thought of that too, but wasn't at
all sure.  I'm in pretty good shape now, but I won't work on it again
until next Sunday.

Northman had written this in response to
http://www.thestuccocompany.com/maintenance/Re-AC-question-what-s-the-circuit-board-in-the-compressor-147038-.htm
 :
I have the same issue and want to bypass the short cycle delay timer, but
just want to verify before I do. I need to remove the com wire and move
the
out wire to where the in wire originates correct?

Richard J Kinch wrote:


-------------------------------------

The board is a delay timer. So that the pressures in the system have
time to equalize before the compressor comes back on.

Sounds like you're over your head, here. Might be time to call an AC
service guy.

--

Christopher A. Young
  You can't shout down a troll.
  You have to starve them.
.

AC question, what's the little circuit board in the compressor
cabinet?

My friend's AC is a Lennox HS26-311-1P.  Its in-house fan goes on, but
the air isn't cooled, and the thing outside makes no noise and the fan
doesn't spin.  (It worked fine all summer and just broke a couple
weeks ago, he happily reports.)

The thermostat is calling for cooling, and the wires from the furnace
where they come into the compressor cabinet have 24 volts across them.

Moving along the wires to their destinations, I find the same 24 volts
between a black wire at one terminal of the contactor and a black wire
at one terminal of a little circuit board next to the contactor.  But
the contactor hasn't closed the circuit.

The board is 2 inches by 2 inches or less and has 3 terminals, in,
out, and ground, or maybe common (I forget).  It has a few each of
diodes, resistors, transistors and a shiny black almost cube, less
than 1x1x1 inch, which I think might be a relay.

What is the purpose of this board, and what is it called??

When I push in the plastic thing in the middle of the contactor, the
compressor goes on and sounds fine.   That's not proof yet that the
problem is the contactor, is it??

I couldn't figure out the diagram inside the cover, or the manual. For
example, it didn't have the circuit board afaict.  I think I have to
make my own diagram, and find out what is the second terminal for the
primary of the contactor.  Is it the small black wire on the same
side, right next to the other black wire that I've already
identified??

A new contactor is about 130 dollars.    This one is 11 years old but
looks like new.  I think if it is broken the odds are 50/50 I can
repair it.  Should I try??

Thanks

On Mon, 18 Sep 2006 02:25:37 GMT, "Stormin Mormon"


Well, I was in over my head, but you answered my question for me!

However, a couple questions you didn't ask, and I didn't answer.

--

Christopher A. Young
  You can't shout down a troll.
  You have to starve them.
.

On Mon, 18 Sep 2006 02:25:37 GMT, "Stormin Mormon"


Well, I was in over my head, but you answered my question for me!

Like "Why is the storming Moron such an idiot?"

Stormin Mormon posted for all of us...


Which would NOT be Chris Young alias Stumped Moron
--
Tekkie  "There's no such thing as a tool I don't need."

check to see if the contactor has voltage across the coil, if it does,
then it's the contactor. otherwise it's you little mystery board.

Empressess #124457


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mm wrote:

I think this summarizes the point I would have gotten to some time
this Sunday.

Thanks everyone.

BTW, as long as the amperage is adequate, do contactors have to be
made for a particular brand/model of AC?  

I remember that I stripped one from a junked compressor unit this
year.  I found it in the basement and it is 80 or 90% as big
physically as my fiend's and looking at it now, it looks brand new and
has about the same arrangement as the one my friend had.  It has a 24
volts coil of course. I'm going to try to find its part number on the
web,

 The board you are talking about is a short cycle relay. It keeps the
compressor from coming on for a set period of time when some knob is
playing with the thermostat. You can replace it, or just take the two
wires coming into the system from the air handler and connect them to
either side of the contactor in a pinch.