Goodman Limit switch questions

So I come home today and crank up the thermostat a few degrees and get on with dinner prep. That's weird, it sure seems a bit chilly when I sit down to eat my dinner...
Go over to the thermostat, and see that although I hear the blowers blowing, the red light on the thermostat is not on as it usually is, and cold air is blowing out the vents.
Trudge downstairs, thinking "ignitor". Poke around there a little, pull the ignitor but it's solid. Look in the bottom half of the furnace, and read the "diagnostic" chart, that tells me what the status light on the circuit board means when it flashes. Re-apply power, both blower fans go on, but no ignition, and the light is flashing 4 times. The chart says that means I have an open limit switch. Apparently there are two? a main and an aux. Try to follow the schematics, and my best guess is that the main limit switch is connected on red wires, and goes into the plenum. Pulled it out, and it looks like a tiny little metal drum on a probe, yes?
There are 3 other little drums that are in the front of the furnace, kind of flush with the bottom, and each has little switches connected to them. I pressed each one a few times, but that didnt' make a difference. Light purple wires on those. Aux Limit Switches?
how much more can I DIY before I call in the big guns? Looks like the mail LS runs about $35? Worth it to just change it out?
this is a Goodman GMP125-4, I'm thinking circa 1996, since the SN starts with 96. thanks for any tips/info.
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barbie.gee wrote:

Never trust blink codes. Sometimes it is right and sometimes it is wrong. Most of us have learned not to waste our time on those. I suggest you get a qualified Service company to analyze that. Its worth it to get an instantaneous fix rather then the grief of trying to second guess the problem.
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That's wise advice. Also, lets say it is a bad limit switch. The switch functioned for a reason. You could replace the $35 swtich, and one of a couple things happens:
* The furnace works fine * the new limit switch promptly blows, cause you didn't fix the problem * There is something serious wrong, and the furnace gives you more trouble before the new limit functions. Might be cabon monoxide, or overheating and catch fire.
The service call could easilly be cheper in the long run.
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Christopher A. Young
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Don Ocean wrote:

Overnight, I figured I know just enough to be dangerous, and not enough to be thorough, so I called a guy out.
It WAS the limit switch, and he had one in the truck. (Now I know how to "jumper(it) out", which is cool!) Since he was here, I had him do the cleaning and maintenance and give the whole furnace the once over, since it was kinda overdue for this year anyway.
So, it cost me about $100 more than if I had done the repair myself, but I gave some money to a local small business, and can feel okay that the repair was done right.
But, I COULDA done it myself! :-) ;-)
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Hmm. Customer who knows how to jump out limit switches. Yep, you're dangerous. Glad your furnace is fixed.
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On Wed, 22 Apr 2009 20:19:21 -0400, "Stormin Mormon"

Almost as scary as a "Stormy" knowing how to jump out a limit switch. Good thing Stormy isnt that bright. Bubba
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I'd call pro. It's spring you know. Birds could be dumping grasses down the flue in an attempt to build a nest (or just end your life, according to Hichcock sp?). Of course, you did say Janitrol/Goodman. It prolly requires a board, like every other Goodman out there. But don't try jumping out limits without verifying what they sense to begin with. And you do know they are prone to the overclamped heat exchanger manufacturing issue right? Like I said, I'd call a pro.
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On Tue, 21 Apr 2009 22:06:10 -0500, "barbie.gee"

Just jump out all those stinkin limits. No need for them. Just a bunch of silly extra parts they add to a system to raise the price of the unit. If the filter is dirty, just pull it and dont put in another. Your system doesnt need one. Its made of metal. Why does it need some silly spun fiberglass material to protect metal?? Bubba
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