Have a new Goodman furnace that has a peculiar issue. The furnace will heat just fine and burners will shut off normally when set point is reached. After the burners have shut down, the blower will run for a minute or so then it seems as though it is given a signal to stop then immediately restart. The blower never stops turning and it wold be best described as someone turning off a light switch and turning it right back on again. After another minute or so the system shuts down as it should. What could be causing this electrical "bump" with the blower motor?

Thanks,
Mike Waters
Lynnwood, WA

A out of range fan and limit control allowing the residual heat left in the heat exchanger to reactivate the blower for a short time.

How new is it? Installer warranty may still be in effect, and poking around may compromise coverage. A call to your installer may be your best next move.

Father-in-law and his ex-heating contractor friend were installers. Got furnace cheap (but new), so no warranty.

Okay then... check the status LED for fault code display while this is occurring.

I just timed the event and it occurs exactly 30 seconds after main burner shutdown. The blower continues to run for another 2 minutes then shuts down until next heating cycle.

I see an LED light that is currently illuminated while the furnace is off. I will count the blinks of this LED the next time the furnace kicks on. Shouldn't be long since it is 30 degrees outside.

In looking at the Emerson control board, while waiting for the system to come on naturally, I saw a button labeled "Fault Recall". Pushing it gave me two sets of 4 blinks. The fault code legend on the furnace panel for 4 blinks indicates that this is an "Open High Limit" condition. Now what?

The system had come on now and run through its cycle. As expected, after 30 seconds a series of fast clicks was heard at the control board and the blower power seemed to be shut off then turned back on within a fraction of a second. NO fault codes were shown by the LED on the control board during this heating cycle. I have made sure there are no restrictions in either the intake or room air side of the furnace.

Loose or improper ground. Loose connection. Bad or defective control board. Bad sensor feeding control board. Those are my guesses since nothing has shown elsewhere.

Any change in diagnosis if I said this was on a 3-month old furnace?

What sensor could be feeding the control board a bad signal?

NO since all those items would have to be tested or replaced to find the problem.

Was the furnace size correctly for your duct work?

I assume it was. The unit didn't start doing this. It took several weeks. I have a tech scheduled to come look at it next Friday.

Has this happened from day 1? Get the "installers" back and have them do it right. Relatives or not, cheap or not, it needs to be made right. And are you sure that Goodman won't warranty this item? Goodman sells through distributors to the public and a warranty is there for a reason. Check around online, do some research before you give up.

Quote:

---

Originally Posted by mwatersjr

I assume it was. The unit didn't start out doing this. It took several weeks.

---

Assume? What makes you assume that the proper calculations were done? Judging by this comment:

Quote:

---

Originally Posted by mwatersjr

Father-in-law and his ex-heating contractor friend were installers. Got furnace cheap (but new), so no warranty.

---

I would make sure of it. I understand the lure of saving money on labor costs but by doing it the shade tree method you are asking for potentially expensive issues down the road that will more than negate the money you saved on labor and losing that warranty doesn't help either.

Back to the warranty issue. Goodman will warranty all equipment if you install it yourself IF... you have the equipment checked out by a licensed professional. Your "tech" may be the one to validate the warranty.

Quote:

---

Originally Posted by Missouri Bound

Back to the warranty issue. Goodman will warranty all equipment if you install it yourself IF....you have the equipment checked out by a licensed professional. Your "tech" may be the one to validate the warranty.

---

While I do believe that the warranty will stand if checked out by a qualified tech, If it is improperly sized you're SOL, likewise with the duct work.

Like I said in a previous post, It took several weeks of use before this showed up. The furnace was replacing an older gas furnace of similar size, CFM output. The tech may be able to check a warranty for it.

Tech came out and scratched his head.. Said he hasn't ever seen a furnace do this in 20 years... Have opened the filter compartment, pulled the filter and let it runs once or twice unencumbered by any possible return air restrictions... same result. I found that I do have the warranty - even registered it with Goodman - Lifetime heat exchanger and 10 yrs parts. I am going to see about getting the control board checked/replaced.