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

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
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mm wrote:

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.
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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.
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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 shortcycledelaytimer, 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:

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

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Stormin Mormon posted for all of us...

Which would NOT be Chris Young alias Stumped Moron
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wrote:

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.
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