[ShonGed]

Draft inducer works, pressure switch works, rollout switch works, surface igniter (41-404) is not lighting up. Igniter itself measures 60ohm which should be OK.
On surface igniter feed lines I am getting 6 AC volts instead of 115V.
If this is control board problem? how difficult is to change? Getting cold
Thank you very much.

[Stratmando]

Are you getting 6 volts at the board and the ignitor? If so check through the components back from the board connections, see where the voltage is being lost.
Relay contacts?
I noticed on the other post a mention of the Ignitor being 6 Volts?

Edit, I just found this:
http://www.drillspot.com/products/34...urface_Ignitor

[ShonGed]

When I disconnect the igniter and measure wires which where connected to the igniter I get 3.5 Volts. Keeping my voltmeter connected, when I start the furnace and my inducer start running my voltage shows 6 volts (instead of 115V).
Also I checked voltage entering the board and it is 115V. From the board wires are running directly to the igniter, so I do not see any other devices in between. I do not know where is relay.

[mygirlsdad77]

Do you hear the gas valve click and gas flow for a short period? If so, and you are not getting correct voltage to igniter, then yes, I would say your board is bad. As long as you get the exact replacement, it is easy to replace, just wright down where all wires go and hook them back up to the new board the same.

[ShonGed]

Thank for your responses. Actually, I do not hear any clicking and I am pretty sure there is no gas flow.
By the way my furnace is 17 years old. Is this a good age for board to go bad?

[Stratmando]

Try these:


Learn about how it works Gas Furnace Hot Surface Igniter HSI

http://www.hvactechsupport.com/furna...e-ignition.asp

[ShonGed]

I replaced the igniter, I replaced the board too. Still getting low voltage (~5VAC) at igniter. Board shows code 31.
Inducer motor starts at 90 seconds (wheel is rotating). When I measure resistance on pressure switch contacts while inducer motor is working is zero (in my mind it means open). All other (3) switch (limit switch) contacts also are showing zero (means open). Voltage to inducer motor is 115VAC.
I do not know what else to do?

[Stratmando]

When a switch is closed, you will have sero volts.
If voltage is going through a series of switches/devices and 1 is open, it should have voltage across the contacts.

[ShonGed]

Here are new developments: Measuring pressure switch.
When there is no power, two contacts of pressure switch have no reading if you measure resistance. Once inducer is on there is no resistance between contacts, voltmeter is beeping same way as you put red and black ends together. But when you measure VAC by keeping one end on one contact and another on ground, reading is only ~2Volts. Do you know what is going on? It should read at list 24VAC. Thank you. Error code is 31.
If I short the switch will this help me to determine the problem?

[Joshdta]

Sounds like you have a pressure switch problem. Do you have 24 volts on either side of the pressure switch? Switch to com on trans

[ShonGed]

Thank for reply. I removed the switch with its tube from the furnace. I placed Ohmmeter on two contacts -circuit is open no sound. Once I sucked on the tube circuit got closed and I can hear beeping. It means that switch closes during negative pressure.
I do not know what you mean by "com on trans". All I checked was one contact and ground then another contact and ground. Reading was 2 or 3 volts.

I still don not understand. Is switch bad or something else is going on?

[Joshdta]

Check for 24 volts between the switch and the common side of the transformer. Or the common on the gas valve. While the furnace is running

[ShonGed]

No, No 24VAC reading. However, as I mentioned before it closes when negative pressure is applied.