New front furnace won't even blow air

[davejay]

hey,
So I put my new suburban 30sp furnace in. Wired it per the intructions, got a 12 volt new thermostat. Pushed the lever to start it up. Nothing... Not even the fan comes on. LP is not hooked up yet. Is there a breaker n the 325 that powers the front furnace? Electrical stuff is not my strong point,..... Help me, said the fly. DJ

[n2916s]

A little confused by "12 volt thermostat" - the thermostat simply serves as a switch -- the operating 12vdc should be directly wired to the plug at the furnace...

[davejay]

Hey,
Well apparently we must use a 12 volt thermostat. The hardware store has very cool thermostats, but they are all 110 volt house stuff. Low voltage needed I guess.

[rmkrum]

Yup. Most of them run on 24 volts AC power...

[streamquest]

You could have a funky thermostat. I experienced the same thing after installing a new furnace. Try bypassing the thermostat by just tying the two conductors together. This way you can at least take that component out of the picture.

Charly

[davejay]

Hey,
I thought maybe I got a bad thermostat, but the directions specificity say, turn thermostat to the off position. These cheap ones don't have an off position. You move the lever all the way left, and the little reed switch goes to off. There must be a breaker for the furnaces. Anybody know.
Maybe an off position sends some sort of message to the board. Can't see how that is any differant than clicking a reed switch to open the connection. DJ

[Grosspoluter]

Originally Posted by davejay

hey,

So I put my new suburban 30sp furnace in. Wired it per the intructions, got a 12 volt new thermostat. Pushed the lever to start it up. Nothing... Not even the fan comes on. LP is not hooked up yet. Is there a breaker n the 325 that powers the front furnace? Electrical stuff is not my strong point,..... Help me, said the fly. DJ

Is it possible with all the new safety features, maybe there’s a pressure safety switch that needs to sense pressure in the LP line?

[DKB_SATX]

So it sounds like you're not yet certain there's power to the furnace (you're speculating about breakers and such.) Do you have a multimeter or even a basic circuit tester? You should make sure power is present and connected at the right places before getting into more involved troubleshooting... sometimes it's the simplest stuff.

[gr.austin]

On my Classic the furnace is 12V. So the t'stat should also be 12V. Check to see if the t'stat is in the heat mode. Also check that the t'stat is wired to the correct terminals for heating. The t'stat wires should either go to a circuit board in the furnace or go to a relay in the furnace control box.

If you can send me a photo of the Furnace control circuit diagram I may be able to help you more. If you can send me a photo of the T'stat terminal strip (where wires hookup)that would also be a big help.

Happy streaming

[davejay]

Hey,
The new furnace has a connection with a red,to power, yellow to ground, two blues for the t stat. Pretty simple. I'll take my fluke to the t stat connections in the t stat. Should have 12 volts there. Other than that I'm lost. DJ

[mayco]

Tie the two blue wires together and test your furnace operation. That will bypass the stat.

[Al and Missy]

Some furnaces have a safety feature that once it is tripped it must be reset by cycling power to the furnace. My furnace has a rocker switch accessible from the outside.


Al

[davejay]

Thanks guys,
I think I'll take it out.....again... And see if there is an on/off switch buy the wires coming out of the case. It could be that simple. I flunked it, and I got 12 volts on the power lead. But no voltage on the stat wires. Tried jumping them, nothing. So there's were I'm at. Thinking of getting dinisour board right from the gitgo, to save me hassle later. Does the new 30 sp suburban have an external on off switch? Thanks DJ

[Al and Missy]

According to the schematic I found, one of the furnace leads should have 12V on it. It is supposed to be connected to the same terminal on the furnace as the 12V coming in to the furnace. The thermostat sends the 12V back to the furnace to cause it to operate. If you don't have 12V on one of the blue wires (according to the schematic I found) the furnace will not run.


That schematic does not show an ON/OFF switch. Another schematic shows a switch on the valve that is NC. It may be sensing gas pressure. You may have to have gas to get the furnace to run.

EDIT: I finally saw the model numbers in the fine print on the schematics. The 30SP appears to have a switch on the gas valve. I bet you need gas pressure to operate it. But it still looks like there should be 12V on one of the blue wires.


https://www.manualslib.com/manual/79...page=35#manual



Al

[davejay]

Hey,
Ok, so I took the furnace out again, turned on its side, right above where the 4 wire white plug is, under the outer case of the furnace, is...... An on/off rocker switch. Flipped it to on, and yup, fires right up. Unbelievable. Who was the genius that decided to put it in a totally hidden spot. All this messing around for nothing..... DJ out...