Went to kick the heat on the other day and it kept faulting out. We're in NW Florida, so we probably only run our heat 3-5 weeks out of the year. Light keeps blinking eight times signaling a Ground Fault issue or ignitor issue. Everytime I reset it the exhaust fan starts, gas opens, glob lights up, ignites flames and fan starts. Runs for about 30 seconds before it trips out again. Ground is good, I've replaced the flame sensor and the control board (w/ a tested used one). Still having same issue. Please help.
If you even breath on those hot surface igniters wrong they can crack. If you’re getting a ground fault code you may have a nicked low voltage wire touching the frame somewhere which breaks the circuit and throws the code. Check pinch points for broken sheathing. Go through low voltage sequence of operation with your meter and the power off and isolate the short to ground. Typically when that happens though it will pop the fuse on the board.
How many volts is the board sending to the flame sensor? If 0 volts it’s a bad board. To test use your meter have one lead on the flame sensor wire and the other to ground.
How many volts is the board sending to the flame sensor? If 0 volts it’s a bad board. To test have one lead on the flame sensor wire and the other to ground.
Check for voltage between your neutral and ground. If you dont have a good neutral or ground on the furnace you can have potential between the two and that will fault out the control. And if its nothing while the furnace is off keep checking while the cycle is running. You should have 0, but anything less than a volt or two would be within margin of error.
Ground and nejtral have to be at or near potential.If you have more than 150 mv.between groung and neutral it can give you issues.any circuit can feedback hot to ground and not trip a breaker if it is a smaller bleed that the breaker is rated for.check between ground and neutral.if you have more than 150mv start turning off breakers until you dont.then try it again.found a high resistance short in a gas dryer this way.the furnace ran fine with the dryer unplugged.
Sounds flame sensor or perhaps low fuel pressure?
I've both cleaned and since replaced the flame sensor.
Flame sensor should have about 90v of AC on it during the start up period. If it doesn’t then the board is bad.
Take out your flame sensor, clean it with a dollar bill (pinch it in your fingers).
Reinstall and try again.
I've both cleaned and since replaced the flame sensor.