No LED status, No 24v and only blower running


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Old 12-02-20, 04:43 PM
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No LED status, No 24v and only blower running

As the subject says my furnace stopped working and after troubleshooting I felt that the control board was faulty as the old board had no status light anymore and when I turn on the furnace the blower just runs and nothing else. I test the transformer by using the same wire that connects from my main to the input side of the transformer along with the neutral and I get 28 volts on the output so the transformer seems good. However when connected to the board the above symptoms persist. I replaced the board and the transformer and that didnít fix the problem. Iím scratching my head on this one. Why am I not at least seeing an indicator on the LED? Anyone have any ideas? Getting colder in Chicago and Iím on day 4 with no heat. I checked all the limit switches and they appear normal but I cannot explain the behavior and lack of any status on the board LED. The replacement board is behaving identically to the old. Can someone please chime in with any suggestions.
 
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Old 12-02-20, 05:12 PM
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Welcome to the forums.

Can someone please chime in with any suggestions.
Since my crystal ball is broken..... a make and model would be helpful.
Part number of the current board is helpful too.

An open safety switch/thermal limiter will keep the blower running.
Some boards will not show a fault..... some will with an open limit.
 
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Old 12-02-20, 06:18 PM
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Bump...... only one thread per topic. I deleted your duplicate thread.
 
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Old 12-02-20, 06:20 PM
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Furnace is a Nordyne FG6RC 120 20c. I did a bit more troubleshooting. Since I have the old board I powered the transformer up using external source of power and then connected its output to the 24v and COM connections on the board and the LED powers up so I donít know why I donít get 24v from the transformer while itís connected to the board for power. Actually I do know because if I have main power connected to the board and the transformer connected to the XFMR and Neutral terminals the board is only putting out about 7.5v where I would expect the full 120v. No wonder the board isnít lighting up.

I tested continuity from the harness that links all the limit switches together and I get continuity (blue wire). See image for schematic.

Schematics for nordyne furnace


Either in doing something wrong or the old board and replacement board are defective in the exact same way which I find unlikely but possible.
 
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Old 12-02-20, 07:28 PM
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There are two hot connections..... L1 and transformer. They are tied together on the board.
There are five neutral connections.... L2, transformer, blower, EAC, HUM. They are tied together on the board.

You should measure 120v between the hots and the neutrals...... if you don't.... it's not getting to the board.
Check the blower switch.
 
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Old 12-02-20, 07:51 PM
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Dude. You totally saved the day. I donít know why I was plugging the hot into eac instead of L1. Must have mixed them up. I could have sworn EAC is where the original connector went. Owe you a beer :-) thanks so much
 
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Old 12-02-20, 08:07 PM
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EAC (electronic air cleaner) is switched 120v when the blower runs.
....................(probably why just the blower was running)
HUM is switched 120v when the burner runs.

You're welcome.
 
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Old 12-02-20, 09:40 PM
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Hindsight is 2020. Diagram shows nothing connected to eac yet I thought eac stood for External AC power :-). What a bonehead. If I was a betting man Iíd pick EAC over something labeled L1 when choosing where the power goes. :-) Expensive lesson between all the parts, hours and portable heaters I purchased this week. Board wasnít cheap. Not to mention the direct line i ran to bypass the transformer terminal so I could get power to the board. Thatís when the controller came to life finally and flashed the status LED 5 times which means 115 VAC was reversed or no ground. Then I saw your post. Embarrassing. Thanks again. Had to get that off my chest. I wired everything back properly including the transformer hack job.
 
 

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