No LED status, No 24v and only blower running
#1
12-02-20, 04:43 PM
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 didn’t fix the problem. I’m 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 I’m 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.
#2
12-02-20, 05:12 PM
Group Moderator
Welcome to the forums.
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.
Can someone please chime in with any suggestions.
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.
#3
12-02-20, 06:18 PM
Group Moderator
#4
12-02-20, 06:20 PM
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 don’t know why I don’t get 24v from the transformer while it’s 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 isn’t 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.
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.
#5
12-02-20, 07:28 PM
Group Moderator
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.
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.
#6
12-02-20, 07:51 PM
Dude. You totally saved the day. I don’t 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
#7
12-02-20, 08:07 PM
Group Moderator
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.
....................(probably why just the blower was running)
HUM is switched 120v when the burner runs.
You're welcome.
#8
12-02-20, 09:40 PM
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 I’d 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 wasn’t cheap. Not to mention the direct line i ran to bypass the transformer terminal so I could get power to the board. That’s 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.
