Goodman Furnace Ignitor Problem GUO75-3 Rev C,S

[iceman]

I'm working on a Goodman gas furnace. The ignitor (B13707-23A) wasn't working so I picked up a new board (B13707-24) as per my local Goodman parts rep recommendation. He said this new board was the replacement. I installed board but still not getting a spark   When I plug in the new board the voltage drops to zero. Any advice would be appreciated.

[iceman]

I forgot to mention that there are no schematics with the unit.

[JWWebster]

Did you check all of the rollouts?

[iceman]

No problem with rollout. I get 24v where the board plugs in but once I plug the board in, the voltage drops to 0v.

[TechGuy]

Something is wrong with the new board.  It draws too much current to drop the voltage. 

Is the old board drop the voltage to zero too?

[jumptrout51]

Verify your neutral and L1 wires.
Also suspect a bad transformer going to ground.

[iceman]

I'm posting as a favor to a buddy of mine who is working on this unit. He said he verified the L1 and neutral wires and transformer seems to be ok. He will check voltage on the old board to see what it shows. I will post when he gets back with me. He already has $100 invested in the new board he installed and he doesn't want to walk away from this job and lose his money.

[jumptrout51]

It may not be a board problem.
Check all low voltage wires for short or ground.

[Icehouse]

Problem: Your furnace will not ignite the gas to produce heat for your home. When a furnace has a bad ignitor what I see most of the time is the following sequence of operation:
 

1. Thermostat calls for heat.
2. Draft inducer motor starts.
3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure  produced by the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas.
Solution: You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem.   The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.

[Icehouse]

Problem: Draft inducer will not start, ignitor will not glow or gas valve will not open.

Solution: Any combination of the above problem or problems could be caused by a bad furnace control board. I always troubleshoot and test the least expensive parts first, such as the pressure switch, limit switch and rollout switches to make sure they are all closed and operating correctly before I go to the control board. First, and most important things to remember is turn your electrical power off to the furnace. Most control boards are located in the blower compartment.  Many control boards have a fuse located on them to protect the board from getting burned up if you have a short to ground. The fuse is usually a 3 to 5 amp fuse similar to the fuses that you might find in a car's fuse box.

[iceman]

Thanks very much for the advice. I am passing this on to the guy who is working on this unit. He will be going back out to the customer's house in the morning and I will let you know if he can get this unit going.

[iceman]

The unit is now running. He told me the common coming off the transformer had to be connected to the ground on the board. This unit was originally a standing pilot furnace that had been retrofitted. Customer told the technician it hadn't worked right since it was retrofitted by another guy quite sometime ago. After several attempts to get the previous guy back out to repair it, he got tired of waiting so he called my buddy. The unit is running ok now. Thanks for all the help guys!