Goodman hard start when cold

Jeff_46

One of my techs had his second service call on a Goodman GMP 100 furnace, 1999 mfg date that starts very hard when it's cold. So much so, that the flames extinguish ... sometimes before the fan comes on. The sensor has the proper micro amps, heat exchanger appears ok (we've serviced enough bad ones, inspected with scope ... no rings in blower compartment), gas pressure is good, w.c. at pressure switch is good, vent not blocked, inducer running full speed, rpms and amp draw ... anyone want to help with this one or at least share a smilar problem and rectification?

hvac64

goodman gmp100

Jeff,, how long is flame staying on?

Jeff_46

varies

sometimes 3 - 4 seconds ... sometimes 30 seconds .... sometimes stays on and runs normal. This happens only when temps outside are colder ... 40 or lower. The tech that's been out there twice is one of my best techs (out of 12). I may pick it up as soon as I show up but it sems as though he's check it all out. Any ideas?

Ken D.

Goodman

Check for defective pressure switch (out of calibration),loose terminals or connections on all switches, controls or components. Be sure none of the safties, limits, or switches are not opening. Press. tubes tight and not cracked.Check for proper polarity on line voltage and check for proper grounding of furnace, controls, etc. If a condensing furnace, check for proper condensate drainage. If all readings and signals are good and steady, I would condemn the control.Intermittant problems seem to be from defective controls many times. Hope this helps.

Jeff_46

Appreciate the effort

The GMP is NOT a condensing furnace. I was hoping for more info than the obvious. Maybe from a Goodman dealer (of which we are not). We didn't install. The installer's nowhere to be found ... imagine that!

Thanx, Ken D. for your time.

Bud_14

Bad Burners?

I can't imagine that, it's a great furnace, kinda like the old cars, simple and straight forward seqeuence. Back awhile ago the inshot type burners had to be replaced, these were covered under warranty. Check with Goodman on this issue, it's a five minute fix. Many techs didn't understabd the way the flame crossed the burners and the problem was intermitent, I've even seen them bend the flame sensor..(not a good idea and you'll be back) Hope this helps out. no guarantees, but it was an issue.

Bud


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Rich W

goodman

Hi Jeff, remove the pressure switch and tube. Point the barb downward and puff in and out on the tube- I'll bet you get water on that non-condensing furnace.I've seen it a lot.
Change the Pr.switch. Good Luck.

Empire_2

Flame cut out

Provided that all electrical failures have been ruled out, Chech This Out. Not only check you manifold press. but also supply at the Gas valve. I can almost be sure that you will find a problem with the meter or incommong line problems. Check the incomming max press on the tag on the furnace and watch your guage as the unit fires. Probably will see a drop out of the valve. Also be aware that on some models, the burners have a problem which causes sputtering on ignition, but I dont think that this is your problem.
Good luck let me know what you find.

Jeff_46

thanx

I will check the burners. Everything else is fine. Thanx, all.

Randy T

Ditto on those burners. Goodman has new beckett burners with a straight crossover, the old burners had an angled crossover. Those new style burners make a tremendous difference.

curiousity kills

goodman

Jeff ask The homeowner if the system igniter has been changed since install.Some after market igniters dont work well because they have too long of a warm up compared to the OEM igniter.Good Luck

Jeff_46

Burners solved it.

It was the burners. Thanx to everyone.

Ken D.

Goodman- Bud.

Bud, Jeff says the burners took care of the problem. I'm curious as to what is it about the burners that cause the problem as Jeff said that the microamps and other readings ok. Does it recycle out on flame failure, high limit, draft, or what? Does it cause a poor flame pattern that it recycles on flame failure? We don't see many Goodmans, so I have not seen the described problem. Thank you for your help.

Bud_14

Flame Pattern

It boiled down to pattern and the flame not getting across fast enough and making the sensor. I'm not sure, it's been awhile but I think the flame was fluttering weird as it crossed. I personally think the problem existed with a combination of draft and flame travel and not just flame pattern, it didn't happen all the time and that's why I'm sure techs were bending the flame sensor.

Glad to see it's working. Nothing worse then freak service problems.

Bud

Rich W

goodman

I'm confused.If the flame travels all the way across and gives a good uA reading-why would the unit shut down because of the burners? If the flame stopped short of the sensor burner-that I could understand. From the first post I assumed there was no problem with flame travel.