York Stellar Plus NG furnace wont' stay running-HELP

York Stellar Plus Natural gas furnace, I bought the house about five years ago so I don’t know exactly how old it is. It is small; only heats back half of house and that consists of only a few rooms.

Sticker says model # P1UDD06N03801A York Stellar Plus Natural gas furnace for furnace.
Situation:
When heat is switched on, the small motor starts running, the pressure switch closes, the igniter ignites gas, and the fan limit thermostat rotates as it heats up. At the 100 degree tab the blower velocity seems to increase, at the 130-140 degree tab the blower velocity increases more, but the temperature seems to increase until the limit switch hits 200 degree tab and shuts it down. Then the cycle keeps repeating. The furnace never continues to run and cannot maintain the temperature that the thermostat is set to.

On my unit, all of the drainage hoses for the elimination of the condensation water are placed over blower motors or over critical circuitry. Leaky hoses have caused moisture to drip into the control boxes and corrode many connections. After cleaning the connections and replacing connectors, the unit still behaves the same. It is a very simple unit and has no error code LED.
Question: What could be the problem, what can I test further myself? How would you begin to troubleshoot this?

Thanks,
JCE

Welcome JohnCEberhart:
You mention 100* tab, 130-140* tab and a 200* tab. I wonder it these thermostats are the nickel-sized thermostats wired in series. If that is the case, you can get a new 200*, hook it up exactly the same as the old one and I think it will make the motor run on high speed. These thermostats are difficult to test because they are all wired together, but a click means it has kicked in and when the 200 kicks in it should kick out the other two.
Another possibility is that the three speed motor is burned out on the high speed. You can disconnect the motor and plug the wires into a receptacle, one speed at a time to see if it runs. The motor would typically have 4 or 5 wires to it, the green one being the mechanical ground, the white one the common, black for low, blue for medium, and red for high speed. Carefully plug the green wire into the half round hole in the receptacle, the white one into the longer plug hole and the colors, one at a time, into the shorter slot.
Please let us know you survived this test and how the situation works out for you.
Glenn

Instead of sticking bare wires into a 120VAC outlet with your fingers, how about we attach this motor to a three pronged cord and test it that way?
If you don't have an old appliance cord laying around, you can buy them at the big box stores for a couple of buck.

Hi Glenn and kok328,

No, unfortunately there is nothing in series that I’ve seen so far. The fan limit thermostat unit is a one-piece part that has a probe that extends into the firebox. There is a dial on it that rotates as it heats up. There are set tabs on it. The installer/consumer can set trip points on the dial. It is currently set so the lowest triggers or trips when it rotates to the 100 degree mark (the blower velocity increases), the second is set to 130-140 degrees (the blower velocity increases again), the last tab is the upper limit switch and is set to 200 degrees (the tab cannot be adjusted up, only down).

Since the firebox temperature seems to increase until the upper limit switch trips, I agree that it seems like the highest speed of the blower is either blown or not allowed to reach full speed for some other reason (hopefully a cheap relay, diode, or thermistor).

I’ll try the wires using an old appliance cord and not bare wires (thanks kok328). I should probably buy more life insurance anyway (keep my wife happy –ha-ha).
What kind of prices have you guys been seeing for the 3 speed blowers (motors)? I am seeing posts here and there that list them as running around a $1000 and no way to repair the control board even if the motor is still good. I am one of the few that used to make a living doing component level circuit board repair. If I can get a schematic, I can repair it.

John

Still failing because I haven't worked on it yet. Heats a little and then resets. Here are some pictures.

Wires to blower are red-low (not connected), blue-med, black-hi, two browns and a white. Browns are connected to (through) what looks like a giant capacitor. Can't see the ground wire yet. I have the schematic so I can check voltages etc. More info soon as I find time to work on it.

200 would be the upper limit and should shut down the burner, try changing the filter and or check the ducts for restriction.

Already did all that. It has a new filter and I removed the ducts to let it run wide open. The limit switch still slowly rotates until it hits the upper limit and shuts down (then repeats the cycle). The airflow is medium, it never goes to high speed. The airflow is probably not good enough to keep the temp from rising to shutdown. Is there a way to force the fan to hi with a jumper like on the old carrier weathermakers?

glennjanie said:

Welcome JohnCEberhart:
You mention 100* tab, 130-140* tab and a 200* tab. I wonder it these thermostats are the nickel-sized thermostats wired in series. If that is the case, you can get a new 200*, hook it up exactly the same as the old one and I think it will make the motor run on high speed. These thermostats are difficult to test because they are all wired together, but a click means it has kicked in and when the 200 kicks in it should kick out the other two.
Another possibility is that the three speed motor is burned out on the high speed. You can disconnect the motor and plug the wires into a receptacle, one speed at a time to see if it runs. The motor would typically have 4 or 5 wires to it, the green one being the mechanical ground, the white one the common, black for low, blue for medium, and red for high speed. Carefully plug the green wire into the half round hole in the receptacle, the white one into the longer plug hole and the colors, one at a time, into the shorter slot.
Please let us know you survived this test and how the situation works out for you.
Glenn

Click to expand...

I'll do this on Thursday or Friday. On my PSC motor the black is high speed and the red is low (according to the schematic and the red wire is currently not and has never been connected to anything).

Hey John:
I see the thermostat, not like I said at all but I understand how that one works too.
I see notes on the blower housing that mention time delays. The time delay is accomplished with relays, the two brown items in the lower part of that panel in your first picture. That's where I'm betting the trouble is. There are lots and lots of different kinds of relays so you will need the old one or complete information from the old one to buy a new one. Getting the wires hooked back the same way is also crucial; you might mark them with notes on masking tape attached to each wire.
If we know the purpose of the relay and understand the information on the relay, it can be tested fairly easy.
Glenn

Hi Glenn,

After I test the blower I'll check out the relays. Relays are usually cheaper than blowers so I hope that's where the problem it. When I first cracked the case open I found lots of leaky hoses dripping water into the control box (and on the relays). I squirted some WD40 on them but had to clean and replace a few spade connectors. The black high speed connector was in bad shape. There's a good possibility that they are stuck open.

Best regards,
John

Hello John:
AAHHHHAA! so the plot thickens. I think you are narrowing the problem down. I hope it works out soon; its 21* here tonight.
Glenn

Hi Glenn,
It not only thickens but it freezes! I didn't get to it yesterday (work gets in the way) but the back half of the house maintained 63* all night despite the 6* temp outside. The old york kicked on and off all night long. Tonight we'll be lucky if it stays above zero. Right now it's a balmy 24 with snow showers and winds gusting to over 30. Wish I was in Kentucky...
Even if I can isolate the problem today or tomorrow, I won't be able to get parts til Monday at the earliest-yahoo!
John

During normal operations I only measured 70 volts at the black wire relay connection when activated (this is a 115-120 volt blower, right?). I connected the black wire up to 120 volts straight into a socket using a plug wire set and the blower seemed to work fine (it didn’t blow up or anything and seemed to be blowing fine). Therefore, I jumpered across the relay so the black (hi-speed) would be at 120V all the time (same as when the fan is set from “auto” to “on&#8221. The ignition controller did not like the fact that the chamber was so cool and would not keep the igniter wire hot. It would shut down and the gas and the burner would never light. Now I understand why the house was a lot cooler when I'd leave the fan running all night, I’ve never seen it do that before. So I connected that the black wire up to where the blue wire was connected and let it run. It seems to take a longer to shut down but it still trips the high limit switch. So here's where I'm at:
If I leave the blower run “on” all of the time it will ignite the burner about half of the time or less.
If I leave it hooked up the way it was originally, it seems to run the blower for a few minutes before the upper limit switch is tripped.
If I connect the black wire to where the blue wire was and leave the blue a wire disconnected it seems to run a little bit longer but the upper limit switch is still tripped. It will not stay running until the thermostat tells it to stop. I can’t tell if the blower is blowing hard enough but it does not seem to be. There are no obstructions that would explain the lack of blower power or air volume output. So either the fan limit switch is not reading the temperature correctly or the blower is not running up to speed.

Hello John:
It looks like we're back to the limit switch. I don't understand why it will not fire up with the fan running. I'm baffled if the limit switch doesn't do the trick.
Glenn

I know it doesn't make any sense. Right now its relays are kicking off and on almost at random (very cold outside) , sometimes ignites and sometimes not. It will run for only a minute at a time- getting worse. When it does run ands gets the flame lit, it shuts down right when the blower relay kicks in. I'll take a look at it and report more in a little bit.

I downloaded the White Rodgers HSI control module troubelshooting guide. What a worthless flowchart!

I've included the schematic but had to break it up becasue of size constraints.

I have to go to Milwaukee for a week so I won't get back to it til next Tuesday or Wednesday

John

Here is the latest strange thing that explains the latest twist of randomness. The vent motor was overheating and shutting the system down. It never got a chance to cool off because it never gets a break. I have a fan on it now and it is back to "normal" fail mode. At least this was logical.

Is the vent motor rated for constant running?

John

John:
I have a question for you? I see none of the obvious restrictions to air flow are present but did you look at the "squirel cage" ,the actual fan blades? They should be cupped and it is possable that after years of corosion and dirt (especialy when there is water acting to solidify or corode) the pitch may not be enough to move enough air to cool down the heat exchanger properly. One more idea that is more likley is with p.s.c. motors sometimes the run capacitors do not put out enough uf or microfarads , being that they are only about 10 bucks a pop i would replace it if you dont have a capacitance tester. to your eye the fan may appear to run at full speed but the limit switch is telling us diffrent. Hope that helps.
Brian

Hi Brian,

I appreciate the advice. That is possible since I have not yet pulled apart the entire blower assembly. I will rip it apart next week and let you know. I have a cap tester but haven't used it since most caps in the past have blown open or shorted out (and catastrophe for some other part near by follows).

John

John,
Found this site by accident tonight. My problem mirrors yours. The York fires, and after 5 minutes shuts down. Do you hear a gurgling sound after yours shuts off? I did. Traced it and realized the drain trap that is screwed to the big blower fan (squirrel cage??) was completely clogged. You posted a picture of this drain trap. By chance did you check it for a clog? I cleaned mine out, and PRESTO! No problems now. I am a complete noob when it comes to HVAC...got real lucky I guess.

Regards,
Brian

briambran said:

John,
Found this site by accident tonight. My problem mirrors yours. The York fires, and after 5 minutes shuts down. Do you hear a gurgling sound after yours shuts off? I did. Traced it and realized the drain trap that is screwed to the big blower fan (squirrel cage??) was completely clogged. You posted a picture of this drain trap. By chance did you check it for a clog? I cleaned mine out, and PRESTO! No problems now. I am a complete noob when it comes to HVAC...got real lucky I guess.

Regards,
Brian

Click to expand...

You mean your furnace caught a "cold" and had drainage problems? -WOW!

I never noticed a gurgle but that doesn't mean it's not the problem. I had the thing off when I disassembled and cleaned up all the parts near the blower but never checked that for a clog. I had a carrier that shut down years ago due to a clogged hose. It was like salt in a cooking show--just a little pinch will do it.

I hope that's it for me too but I'm not sure. This furnace is not an Einstein. It has no smarts at all. It's funny, I have another carrier weathermaker (I don't think they make that one anymore) running the front half of this house just like my old one and this is one smart machine when compared to my simpleton york.

I'll be looking at it tomorrow or some days thereafter. Man is it cold here!!!! And now the snow is coming again.....I'll let you know.

Thanks Brian!

John