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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7724
Experience:  Furnace, A/C and heat pump specialist.
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I have a nordyne gas furnace model no. GL1RA 072C-12A that

Customer Question

Hi Tim
So I have a nordyne gas furnace model no. GL1RA 072C-12A that is flashing once, replaced the mother board (hooked up a digital multimeter to the gas solenoid and got no tone) and ensured the limit switch is good...out of ideas!
JA: Did you double-check the thermostat? And what about the pilot light?
Customer: yep. good
JA: Do you plan on doing the work yourself?
Customer: yep
JA: Anything else we should know to help you best?
Customer: no
Submitted: 17 days ago.
Category: HVAC
Expert:  BillyHvac replied 17 days ago.

Hello,

When you shut off power and turn back on, does it go straight to blinking?

Customer: replied 17 days ago.
No, blinks right before flue blower comes on and then once every 4 secs or so...
Expert:  BillyHvac replied 17 days ago.

Thank you,

What all limits did you test and how did you test them

See here

Customer: replied 17 days ago.
just touched both terminals (of the gas solenoid) for resistance... got like 12 ohms, touched one lead to ground, got nothing, touched the other lead to ground got nothing (had the meter on sound).
Expert:  BillyHvac replied 17 days ago.

when this first happened was the filter plugged?

Customer: replied 17 days ago.
no, filter was replaced about 2 months ago (was clean when I pulled it) and has since been removed
Expert:  BillyHvac replied 17 days ago.

Ok we are going to eliminate one at a time.

Number 11 on the chart I sent HEREPower oiff...remove the 2 wires, connect direct together (a small nail, staple or paperclip inserted into each wire end connector works well).

with wires connected directly together turn power on and tell me code.

Customer: replied 17 days ago.
sorry, what page?
Expert:  BillyHvac replied 17 days ago.

Look for the blue hilights

Like HERE

Customer: replied 17 days ago.
this is for the limit switch?
Expert:  BillyHvac replied 17 days ago.

correct

Customer: replied 17 days ago.
stand by
Customer: replied 17 days ago.
status light still blinking once (I removed the limit switch from upstairs to the one downstairs a few days ago...no love, but then reinstalled the one from downstairs into the "good" upstairs and it worked just fine).
Expert:  BillyHvac replied 17 days ago.

thank you....now we want to move to the rollouts......follow the wires from the limit you just checked. The wires will leapfrog to limits before returning to circuit board...we want to check all these...the roll outs by the burners have tiny reset buttons in center.

Also if you can post a pic of your furnace with doors off I can draw locations for you

Customer: replied 17 days ago.
red buttons (two dime sized ..near the burner assy) are good, they do not push in! Pics on the way!
Customer: replied 17 days ago.
keep getting an error message....let me resize (5.2mb now)
Customer: replied 17 days ago.
how about that?
Expert:  BillyHvac replied 17 days ago.

thank you,

If you follow the wires from the safetys you have found...do any of the wires lead to the blower (bottom) compartment

Customer: replied 17 days ago.
they do, checked the leads and wiggled, all good!
Expert:  BillyHvac replied 17 days ago.

did you bypass the switch as described earlier?

Customer: replied 17 days ago.
the limit switch (approx. 2x4 phenolic panel). Attached is pic of limit switch u asked me to jump.
Expert:  BillyHvac replied 17 days ago.

yes...but have you been jumping each limit the same way to eliminate?

Customer: replied 17 days ago.
no, so the house blower is a huge plug (at least 4 wires), do you want me to jump that the same way?
Customer: replied 17 days ago.
i'll need 4 paper clips?
Expert:  BillyHvac replied 17 days ago.

we will not jump anything except the limit switches...no blower wires..

Post pic of where the wires from phenolic go to blower section

Customer: replied 17 days ago.
btw, blower to house is turning on (along with flue blower)...still want pics?
Expert:  BillyHvac replied 17 days ago.

Yes....when a limit is open the main blower runs by default

Customer: replied 17 days ago.
right side
Customer: replied 17 days ago.
left...
Customer: replied 17 days ago.
does that help? Or do you need another pic?
Customer: replied 17 days ago.
does that mean it closes when hot?
Expert:  BillyHvac replied 17 days ago.

ok imagine this...

The circuit board has a wire that leaves it on the the way to the "limit" loop. It goes through each limit leap frogging until finally the wire returns to the circuit board. Somewhere in the loop is an open contact.

I need to follow the wires safetys until you cover everything in that loop....

Customer: replied 17 days ago.
ok, do I jump anything along the way?
Expert:  BillyHvac replied 17 days ago.

everything in that loop one at a time...until the light goes solid

Customer: replied 17 days ago.
roger!
Expert:  BillyHvac replied 17 days ago.

have to sign off for a while, but will repsond as soon as I can.

Billy

Customer: replied 17 days ago.
ok, tried everything
Customer: replied 17 days ago.
no love on all the jumps
Expert:  airheatman replied 17 days ago.

Let's do this.SINCE WE ARE GETTING A LIMIT ERROR> Note there are 2 blue wires leaving the 9 pin plug on board. One leaves board and goes through all limits and then returns to board proving the circuit is closed. Unplug the 9 pin plug and stick the leads from your meter into the unplugged harness between pins 3 and 8 and see if we have continuity.That will tell us if there is an pen limit in the circuit or not.

Customer: replied 17 days ago.
I get no audible beep when I touch the dmm to the blue pins, but what is strange, when I test any sets of pins I get nothing! User error?
Customer: replied 17 days ago.
meaning orange/orange and yellow/brown
Expert:  airheatman replied 17 days ago.

Are you sure you found them all? rollouts near burners,main limit in furnace vestibule exhaust vent and on blower housing are likely places you may have them.I would start at board and visibly trace blue wire to verify all the way back to board.Most likely overlooked is one in blower housing.

Customer: replied 17 days ago.
no, just the ones in the 9 pin plug... i'll check now!
Expert:  airheatman replied 17 days ago.

OK the reason you get no reading on orange orange is because the pressure switch is "open".It does not close until inducer motor comes on. Yellow brown are low voltage out to gas valve.

Customer: replied 17 days ago.
the two flame roll out switches are good (took the wires off, got an audible sound for both), the 4 pins going to the blower are good, flue blower is good... but can't get anything on the 8 and 3 pin nor the gas valve...
Expert:  airheatman replied 17 days ago.

You have to have a break somewhere in the blue wire if you do not get continuity between the blues. Until we get continuity, board is not going let 24v go to the valve.

Next I would put one meter probe into one of the blues on socket.Then leaving it there. Go to every limit in circuit and check both sides until you find where we do not have continuity.(Note touch leads together first just to veirfy meter is working)

Customer: replied 17 days ago.
yeah I have a complex dmm isn't working so I touch the leads regularly to verify that it is...ok, I'll try that!
Expert:  airheatman replied 17 days ago.

We have to find the break.If you want to prove this is the issue.(if you have a couple of wire nuts) cut the blue wires just outside the 9 pin and connect the ones from the plug together just for a test to see if furnace works. Of course this is only for a test and you will need to reconnect correctly.

Customer: replied 17 days ago.
I just noticed something, my blue 3 pin goes to the limit first then the flame roll out...did I just do a rookie move or does the logic from the board allow this?
Expert:  airheatman replied 17 days ago.

It really makes no difference They are all in series.Remember the old Christmas bulbs where if one went out, they all went out? THis is about the same. That blue has to leave board go through all limits and come back.

Customer: replied 17 days ago.
no, it has to go to the limit first, otherwise it only goes to one flame roll out (on top) then back to the board skipping the others. I'm thinking taking the blower out, that switch I can't get to...and the only other wires out of the blower are the one out of the motor!
Expert:  airheatman replied 17 days ago.

AS state, it can go through any one first as long as it goes into one ,then out to next through each one,but I usually wires per mfgr diagram.Lets check the one on blower.They are known to fail.

Customer: replied 17 days ago.
ok, this one is gonna take a while, removing this will be fun! Ya know, the blow only turned on once, every other time I flipped the switch for power the blower didn't turn on...only the flue blower!
Expert:  airheatman replied 17 days ago.

Take your time. AS mentioned if you don't mind a wire connector you can cut the blue wires to and from and tie them together to see if that is the problem

Customer: replied 17 days ago.
got continuity across the blower switch and re-installed it and the system worked but the house blower did not come on...allowed the manifold to run like a minute before I shut it down, I was getting nervous the house blower wasn't turning on, was that premature?
Expert:  airheatman replied 17 days ago.

Blower should be on before a minute. Try again and as soon as burners light , put meter leads on Neutral and HEAT terminals on board and watch for voltage. Within about 30 seconds we should het 120v between those terminals.

Customer: replied 17 days ago.
tried it again before your post, limit switch killed the manifold, blower did not turn on...took blower out inspected wires, re-installed and now it's working...thinking I need a blower this one is on it's last leg... do you want me meter the neutral and heat term?
Customer: replied 17 days ago.
tried it one last time just to get repeatability and the flue kicked on then kicked off and did that in rapid succession multiple times (rev'ing faster each time) before I killed it, flipped the switch on again and everything ran perfect...any thoughts?
Customer: replied 17 days ago.
is still running ok...
Customer: replied 17 days ago.
weird no?
Customer: replied 17 days ago.
the flame cut out again, killed power to the furnace, then turned it back on again the again the flue blower would spin then cut off then spin again then cut off in rapid succession...any thoughts?
Expert:  airheatman replied 17 days ago.

You could also have a board failing or loose connection from all we have done.Inducer should keep 120 all the time. Check and make sure wires are making good connection from inducer to board.

Customer: replied 17 days ago.
I just put in a new board, that was yesterday...thinking my old board was good!!! So checked all connections (including inducer)...all seemed good, flipped the switch...went back to one flask....muddered something I won't repeat...cut power, rechecked connections, flipped power back on and everything cycled correctly... I am clueless as to what is going on!
Expert:  airheatman replied 17 days ago.

Well we know that switch you bypassed and made it work needs to be replaced.

Customer: replied 17 days ago.
I didn't bypass anything... and connections seem to be good!
Customer: replied 17 days ago.
gonna turn on furnace see what happens!
Expert:  airheatman replied 17 days ago.

My bad, I thought you had bypassed the one on blower.Let me know if furnace works now

Customer: replied 17 days ago.
weird, flue blower did the same shut off in rapid succession thing again, flipped the power off and then on, got a one flash, re-checked wires flipped back on and all seems ok...again.
Expert:  airheatman replied 17 days ago.

If inducer motor is still cutting in and out we need to determine if the power is being lost from board or not.If so, Try bypassing thermostat by connecting R and W (where thermostat wires connect)on board and see if it will stay on

Customer: replied 17 days ago.
the top red and the bot***** ***** correct? Also when all seemed to be running ok, I lowered the temp on the thermostat and noticed the big blower stayed on...until I killed power to the furnace...any ideas?
Expert:  airheatman replied 17 days ago.

Wires you want to check at inducer for 120 to see if cutting in and out here.

AS for bypassing thermostat R and W as shown here

Customer: replied 16 days ago.
thermostat no love...even though the thermostat is set below the desired limit the flue blower turns on...hooked up the leads from the dmm to the inducer with the wires connected and I got 18v...???
Expert:  airheatman replied 16 days ago.

With R and W jumped at board thermostat is out of picture so it will make no difference what it is set to. If you do not get 120 out of board to inducer with R and W jumped, we should still get a code .

Customer: replied 15 days ago.
ok, so I can get it to run (seems like I have to play with the pressure switch wires every other time the furnace runs) but when the house gets up to temp the burner cuts out but then the big blower never shuts off and the system tries to start again with the flue blower turning off and on before I cut the power... I'm getting 120 volts btw... System just wants to re-start until flip the switch and "reboot" the system!
Expert:  airheatman replied 15 days ago.

This s sort of sounding like you may have another bad board.I am going to open to other experts to see if they have ideas.

Customer: replied 15 days ago.
tomorrow I'm gonna switch out that board for my old one and see what happens
Customer: replied 14 days ago.
an update...I did switch out my old board and the furnace would run for one good cycle, then shut off, bypassed all switches by connecting the 8 and 3 blue wires and runs fine...so obviously it's a switch, thank you for all your help! Just can't wrap my head on why one good cycle and then no love, especially when I get tone at each switch!