Before removing the processor board, check the following areas:
- Use output test to verify problem
- Check the 24 VAC fuse
- Replace the comparitor, and test
If that doesn’t work, try the following steps:
- Replace the processor board with a “known good” one
- If the processor board seems bad, check eBay for replacement or repair service
- If the processor board is good, then replace the motherboard
- To repair the motherboard, use this diagram to isolate the bad trace
- If the motherboard and processor board are good, then use this diagram to test for wire continuity
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