Need help troubleshooting a new installation of a Goodman 70K btu 95%
efficiency two stage gas furnace (Model GMH950703BXA). Brand new.
Replaced old furnace with new. Unit ran fine for about 30 minutes and
then cycled itself off. No flashing diagnostic light until tried three
times and then single diagnostic to indicate three failures and that
gas not being delivered to burners.
Gas pressure fine.
Unit cycles on, blower runs, igniter heats up but after 15 seconds
igniter turns off because flame senses nothing. Not sure why it will
deliver gas to burners anymore. I checked the gas valve while running,
after igniter heats up, I can confirm valve does not open. I know
valve is not the broken because I took valve from another new unit and
still same results. In fact, tried replacing every part except the
The only thing I can think of is that we did not do the direct
venting. While testing, left air inlet as is and combutsion out was
vented to existing flue from old furnace (4" flexible tube).
If venting was the issue, wouldn't the unit at least burn for a time
and then cycle off ? Now cannot get any gas to be released by valve to
the burners. Tried turning off gas, shut off gas valve, shut off
electricity, and re-started everything again, but same results. Tried
4 or five more times.
Any suggestions would help.
You tried a gas valve out of another new unit?
Did you try another control board? (Maybe I missed that...)
Does the pressure sensor close after the inducer runs?
I gather this is some temporary setup with venting.
Don't see how that would affect it.
Is the electric service to the furnace control properly
Grounded AND is the polarity correct? (Wh Neutral, Blk Hot)
The control is very sensitive to those conditions.
Is the gas valve getting power during the ignitor warm up? If so,
you likely have a bad gas valve. If not, I'd look for some notes
about how many amps the HSI draws. I worked on a unit that had a
HSI that glowed nicely, but the amperage draw was wrong. So, the
valve didn't think the HSI was working properly.
Christopher A. Young
You can\'t shout down a troll.
On Feb 20, 2:18 pm, email@example.com wrote:
I had the same problem a coupla months ago with my 90K BTU Goodman 95%
2-stage furnace. The contractor installed the brand new unit, and
after a couple of days the furnace started behaving just like yours
is. I called the guy, he came back, opened up the front cover, looked
inside, but wasn't sure what it was, but somehow got it to work. Over
the next few weeks the problem reoccurred a couple more times, once or
twice it self-healed, but then it wouldn't come back on, so I called
the guy again. The second time, hew finally figured it out, and was
able to fix it. The furnace has been working fine for 4-5 weeks now.
Here's what it turned out to be:
If you remove the front cover, there is a black rubber hose inside,
about 5/8" thick, that is used to remove H20 condesation (from the
exhaust) and drain it out of the furnace (thru a pvc pipe.) Well, this
black rubber hose was originally about 2+ft long(orig. length "out of
the box long"?), so it was "bent and curved" by 180 deg inside the
furnace when installed. There was a section of the hose that was
forming a slight U-shape, and it seems that some H20 was just sitting
in there instead of being drained out. That's at least how the guy
explained it to me, and he thought that, for some reason, was causing
the furnace to go into lockout.
Solution: The guy used a pair of scissors/cutters to trim the rubber
hose to the total length of maybe 10 " and ran it to the drainage
opening (on the right-hand side of the furnace) in a pretty much
straight, slanted line.
I hope I am explaining this clearly enough. I was getting so pissed
and frustrated for a few weeks, and wouldn't want anyone else to have
to go thru the same experience.
Please post an update as to whether you were able to get your furnace
fixed. I'll be very curious.
I had exactly the same problem. I had tried everything I could think of.
Finally I called the installer since the furnace was only 3 years old and still
under parts warranty. He was scheduled to come out the next day. While I was
waiting for my wife to dress to go shopping I decided to do an internet search
and found this write-up. After reading about the condensation drain hose problem
it referred to, I went and squeezed the hose over its entire length since it was
very flexible. I then made sure the hose had a drain slant (i.e., no dips) over
its length. I estimate that about a pint of water drained when I did this.
After that I turned on the furnace and it worked like a charm (at least so far).
Thank you for your input!
On Thursday, January 2, 2014 at 7:44:01 PM UTC-6, Bob wrote:
Bob ... You are a genius. How you determined that the problem was the hose
filling up with water is beyond me. I disconnected the hose which had a sli
ght "belly" in it, drained a half pint of liquid, shortened the length of t
he hose, and reconnected it... making sure it was on a continuous slant dow
nhill the entire length. Furnace worked like a charm !
I was curious why the furnace worked all last winter but I figure it was in
itially installed in the dead of last winter when there was low humidity. t
he condensation never built up until I started it up this year. Thanks aga
Our furnace is Carrier 96% model. No hose. Rigid PVC small dia.
pipes connected to AC evaporator pan drain then straight down to
drain in the basement floor. No such problem either on AC or
furnce. I bet the problem will recur unless you make sure same
standing water problem happens.
On Thu, 2 Jan 2014 20:41:13 -0800 (PST), " firstname.lastname@example.org"
Nope - it just threw the pressure balance off and one of the safety
"sail switches" would not turn off or on - preventing the unit from
On 1/3/2014 8:01 AM, email@example.com wrote:
I had an Amana high efficiency unit in my previous house and it had a
similar problem. Because the combustion air on this model is from
inside the house (basement), it would pick up any dust, etc. in the air.
This particulate would then form what I referred to as slime balls
inside the drain tubes. There were 2 drains, one from the combustion
blower and one from the secondary heat exchanger. Usually the one from
the blower would clog. Initially it would start and run for a really
long time before combustion. Apparently, it would have to slug enough
water away from the blades in order to get enough negative pressure to
then allow the gas valve to open and start. If you let it go for a long
time, eventually, it would never open the gas valve; only the combustion
blower would run. I found that, because of the basement layout, when
the furnace was installed, I had to change the side where the drain was
located. So, there was a small coupling in the drain line. The line
was PVC with a short rubber hose on each end. Apparently, the roughness
inside the solid pipe, where the coupling was located, was enough to
catch the 'slime balls' and would build up until the line was clogged.
I changed out the drain line to a single clear plastic line. Now you
can actually see if a clog was forming. But, because there was no
roughness inside, it never did. However, I would periodically take out
the drains and clean any deposites with a small bottle brush and lots of
What about condensate drain?
If in lpock out mode, it takes I think 2 hpours
before you can start the unit again. You can rest the unit
by turning power on/off. Control board has test point to ground to
test the unit. Tried or cleaned flame sensor?
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