quote:

Originally posted by hvactech:
12GA glad to see you take caution with power. Turning off the furnace switch is all you need to do.
Skins2881, you are correct with the Blue wire as possible common. I tend to hesitate instructing such without more detail.

We'll that worked out great - thanks for the advice. The air conditioner is running and cooling down the house but now the thermostat indicates that it's running on battery. Not a problem for tonight but at some point I'll have to see about connecting the unused blue wire to C if I understand correctly.

Thanks to all for the help.

quote:

Originally posted by 12GA:
but now the thermostat indicates that it's running on battery.

Did you install the batteries correctly? One is opposite of the other, even though both springs are on the same side.

Because the stat has a 'replace battery' indicator and no such 'running on battery' indicator.

quote:

Originally posted by Excam_Man:

quote:

Originally posted by 12GA:
but now the thermostat indicates that it's running on battery.

Did you install the batteries correctly? One is opposite of the other, even though both springs are on the same side.

Because the stat has a 'replace battery' indicator and no such 'running on battery' indicator.

My poor eyesight mistook the temperature HOLD indicator for a battery symbol. Time for some stronger cheaters.

Thanks for all the help, fellas. I could not have done it without you.

And I'm back. Typical Spring weather brought temps down to the 40's last night, and with a few windows left open, down to 62* indoors. I go to turn the heat on for the 1st time with the new stat this morning and I hear the furnace turn on, but fails to light and eventually turns off after a minute or two.

Do you think this may be related or a separate issue from my wiring of the new stat?

quote:

Originally posted by 12GA:
And I'm back. Typical Spring weather brought temps down to the 40's last night, and with a few windows left open, down to 62* indoors. I go to turn the heat on for the 1st time with the new stat this morning and I hear the furnace turn on, but fails to light and eventually turns off after a minute or two.

Do you think this may be related or a separate issue from my wiring of the new stat?

Separate, you likely have a bad igniter. After a couple tries it will go into lock out.

Brand and model number?

It's a GMC "Dependable Ninety-Two".

quote:

Originally posted by 12GA:
It's a GMC "Dependable Ninety-Two".

Yeah, that's a Goodman product. The model number will be on the inside of the furnace on a white label.

If your furnace has the older style igniter, you should see a burnt (white) spot on one of the center two of the 4 element tracks.

Blinking LED, the label on one of the doors will give an idea of where the trouble lies. I would say it will likely be "ignition failure". Which is a common problem with the older Goodmans.

The new 'upgraded' igniter will be silicone nitride instead of silicone carbide. The carbide ones will break like a pencil lead. The nitride ones are more durable and last longer. You want to hold and install the new one by holding the white ceramic part. As you don't want to touch the heating element.

Model and blinking code... ?

quote:

Originally posted by Excam_Man:
Model and blinking code... ?

Model GMPN080-4 REV B

I don't see a flashing light when I peer through the little round window. Does the furnace need to be cycling in order for that to happen?

quote:

Originally posted by 12GA:

Model GMPN080-4 REV B

The OEM board in that furnace has a light (as should any replacement). Turning the power on/off, resets the board.

Sequence of operation:
Stat calls for heat, pressure switch open, inducer motor starts, pressure switch closes, should then hear a 'relay' click to power the igniter, after it warms up and glows bright, you hear another 'relay' click to power the gas control, then you should hear gas flowing from the manifold, burners should light up.

Opt 1, If you don't hear the first click, the pressure switch isn't closing.

Opt 2, If everything above is in order, you hear the second click and gas flowing, but have no glowing, the igniter is bad.

Opt 3, If everything above is in order, you hear the second click and no gas flow, but have a bright glowing igniter, you have an open rollout/limit control. Could also be the gas control, but very unlikely.

Above is the three most common issues with this model. Along with a dirty flame sensor, but this can only be a problem *if* the unit actually lights up (you stated it didn't).

I made a video hoping that it would be helpful in diagnosing the problem. My apologies for the shaky camera work.

Inducer runs, igniter is glowing and at 33 secs, 1 min 30 secs and 2 min 27, you can hear the second relay click. Which is supposed to be powering the gas control.

I hear no sound of gas flow. Which means one of the safety limits in series with the gas control is tripped/bad or the gas control is bad (not likely).

#1 would be the 'pressure switch'. Make sure the contacts are closed after the inducer motor gets up to speed. Should be ok, or it wouldn't proceed to the second 'click'.

#2 would be the 'stack overtemp switch', it should be closed at room temp. This switch is an auto reset type.

#3 are the 4 'rollout switches' which should all be closed at room temp. These switches are manual reset type and something is very wrong, if one is tripped.

24v (+) power---PS---SO---ROS---ROS---ROS---ROS---GC---ground (-)

PS, pressure switch
SO, stack overtemp switch
ROS, rollout switch
GC, Gas Control

At this point in the diagnostic, I'd say it's one of the 4 rollouts. If so, you need to know/find out *WHY* it tripped.

***The GMP and GMPN are known for having bad heat exchangers. Which lead you to the tripped rollouts. Can be other things, but this is the most common one with this type of failure.

At this point I'd recommend calling a licensed HVAC tech to come out and diagnose and fix the unit.

Any update?

quote:

Originally posted by Excam_Man:
Any update?

Finally got around to having a service tech look at the furnace. He diagnosed the no gas flow problem as a plugged heat exchanger. Unfortunately he also found a crack in the heat exchanger while unplugging it so it looks like I’m in the market for a new furnace.

What do we like for furnaces for a small home (less than 2,000 sq ft)?

We really like our Nest

quote:

Originally posted by sigarms229:
I have an Emerson Sensi wifi thermostat that I am VERY happy with! Bought it last June and I have zero complaints thus far.

I am on my second set of three of these (left the others at a sold home) and love it. I chose this over the next for price and the fact that I really didn't want to have to work around something that is trying to learn patterns.

With the Sensi I have 2 or 3 different sets of programs I set up to meet our needs depending on who is there and when. Of course can also "hold" temp at a setting and turn back up/down when returning from a trip via phone or computer.

I need a furnace now. My thermostat needs have been met. What do we like for furnaces?

Are you saying he pulled the heat exchanger and found a crack. Does your furnace have a metal prob 4" metal exhaust pipe or pvc. On the control board down in the blower section there is a red led light. Take both doors off the furnace have the tstat set to heat. There is a safety button the lower door presses push that with a finger, the system will cycle three times then blink a code. From what your describing either may be a bad pressure switch, some blockage in the venter motor or possibly a bad control board. Most furnaces will not let the igniter come on if there is a failed safety in the venting exhaust. Lastly make sure no one turned off the gas to the furnace.

The service tech said there is a crack in the heat exchanger and if I run the furnace I risk carbon monoxide poisoning.

quote:

Originally posted by Excam_Man:

quote:

Originally posted by 12GA:

quote:

Originally posted by jimmy123x:
If you have a heat pump, you need a thermostat compatible for a heat pump, but they're pretty easy to change, just dont get the wires mixed up. Most a/c guys here use honeywell.

I have central air and a natural gas furnace with forced hot air heat (ductwork). Would something like that have a heat pump.

Any entry level HVAC guy should know by the photo, that this is a straight heat with air conditioning stat. As the thermostat doesn't have connections for a heat pump (O/B, Aux-E)

RH/RC - Heating and Cooling Power (wired together)
W - Heat
G - Fan
Y - Cooling

For a simple stat, I like the Honeywell # TH5110D 1029 (large screen)
Programmable Honeywell TH6220D 1028 (large screen)
Touchscreen Honeywell TH8320R 1003 (VisionPro 8000)

Here's a good company, if you want to order one online:
http://www.supplyhouse.com/Hon...4Ji0mTP0rhoCSXjw_wcB

What picture? There is no picture posted. Yes a heat pump has the same wiring in addition to an additional wire which I think is orange if memory serves me right for the reversing valve (5 total wires) I have no idea about gas furnaces as we don't ever use them here.