Carrier Weathermaker 2900: PCB problem?

Hi ppl.
Carrier Weathermaker 2900. Approx 4 years old.
I noticed the blower wasn't working when thermostat kicked in. Went to basement, opened machine. things appear fine, but per service-sheet there is no light coming from LED.
Tested with VMeter for ~110 at L1/L2 and 24 VAC at S1 S2. All checks out. (although the xformer seems to buzz slightly, but I guess that could be normal.)
Fuse looks good 2. Even with service-switch closed, I can't get LED to come on. (although it did come on once for me, but I can't seem to repeat that... strange fluke.)
anyway... does it appear that I have to go spend $200 on a new "hk32fz011 PCB for this unit?... grrrr.. way 2 much $$ for that part....
Does anyone know of any component-level issues that can cause this sort of failure... as I would prefer to replace that part obviously... (althogh if the DIAG-piece is busted, it could be the main ICs that are fried, and thats the end of that...)
Is the PCB the problem for sure? (obviously I don't want to spend $200 on a part that isn't the problem...) [ should I pull*all* the wires OFF and try to run it with just the power-feed attached to trully isolate the problem, or is that not worth it. ]
Any assistance/insight for a HVAC newbie would be much appreciated.
thanks -- MikeE
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? That's pretty cheap. I would have a more experienced diagnosos before I started throwing parts at it though.

Doubtful.
It wouldn't be worth it.

Get the opinion of someone, i.e a contractor, so you can be sure that the part you're testing is in fact the problem. It's just too hard to guess over the internet.
- Robert

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I would umplug the unit for 20 minutes and see if it resets itself. Do you have a condensation pump? Check to see if it is full or the safety is malfunctioning.

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