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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7602
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a York Stellar Plus model # p2udd12no7601c furnace.

Customer Question

I have a York Stellar Plus model # ***** furnace. Two weeks ago, it wasn't working, basic checks revealed crumbled hot surface igniter and blown fuse @ side switch. New fuse and igniter fixed for about a week, stopped working, checked out to be same symptoms, crumbled igniter and blown fuse. Replaced igniter and fuse, furnace worked for a couple hours, then blew fuse, this time igniter still looks fine. I thought I'd run this by you before throwing parts like new circuit board at it trying to make a laymans semi educated guess at what my problem might be. Thank you in advance for any advice.
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Do you have a volt meter to make sure we do not have high voltage going to the furnace. The fuse is usually due to a short which could be in a wire or one of the components as well as the board, but this igniter crumbling is something highly unusual.

Customer: replied 1 year ago.
I'll be back there with a voltmeter shortly. Also FYI the 1st crumbled igniter was years old, 2nd may have been wrong part, parts place told me it "should" work but didn't have o e m just if that helps, I'll let you know when I'm there with voltmeter
Expert:  airheatman replied 1 year ago.

OK another thing you might do is watch and see if igniter is going out after burners ignite If not this can cause overheating .

Customer: replied 1 year ago.
It is checked that
Expert:  airheatman replied 1 year ago.

OK .Possibly the second could have crumbled if incorrect one. but we still need to determine what is popping fuse.I would start b looking at wire between thermostat and units to make sure squirrels or something have not chewed wires or nothing skinned tat might be touching metal cabinet on units.

Customer: replied 1 year ago.
Ok about to check that. At furnace and nearby outlets 116 volts as far as possible high voltage goes.
Expert:  airheatman replied 1 year ago.

That is fine.We could be as high as 132 without issues.

Customer: replied 1 year ago.
I don't see anything visibly wrong, or contacting from thermostat wires. Cover was removed and don't see any burned spots or other witness marks on control board. There is a diagnostic light but I'm not sure how to get it to flash a code if that would be useful
Expert:  airheatman replied 1 year ago.

Finding a short can be troublesome.Do you have any idea at what point the fuse blows?

Customer: replied 1 year ago.
I don't. earlier was able to start and run furnace through several forced on off cycles seemed fine. Left for a couple hours was blown again upon return.
Expert:  airheatman replied 1 year ago.

There usually when a unit runs awhile and then blows fuse is because something changed during the cycle. You do not have a heat pump working in conjunction with the furnace do you?

Customer: replied 1 year ago.
No just furnace and a/c
Customer: replied 1 year ago.
As far as system, just furnace of course as far as what's running
Expert:  airheatman replied 1 year ago.

The reason I asked is I have seen the control wiring up against a hot gas line in a heat pump that would allow a bleed of voltage through skin of wire when it got hot. I am suspecting you have something going on with that control board .

Customer: replied 1 year ago.
Those were my thoughts....so if fuses keep popping try replacing control board? Or is there a way to test it?
Expert:  airheatman replied 1 year ago.

Unfortunately the only way we could test to be sure if it was popping immediately.If it were, we could disconnect wires to thermostat and components to see if it popped, but since it is erratic, not really any way to simulate the issue.I hate condemning the board via internet but at this point that would probably be my next step.

Customer: replied 1 year ago.
It also seems the furnace runs exhaust blower etc for several minutes after thermostat signals on. Stops and starts flame a couple times before reaching heat setting and runs for several minutes after reaching desired heat before stopping. Not sure if this is just an observation or indicative of anything
Expert:  airheatman replied 1 year ago.

All of this erratic behavior is characteristic of a failing board

Customer: replied 1 year ago.
Ok thought that might be. Thank you for your help I'll install a new board tomorrow and let you know if I have further ?s
Expert:  airheatman replied 1 year ago.

Sounds good

Customer: replied 1 year ago.
Found and insulated short that was blowing fuse and hot surface igniter. One of the plastic coverings had worn through and was allowing intermittent metal to metal contact between the leads to igniter and combustion box.
Replaced control board. Cleaned flame sensor.
Furnace continues to short cycle though. Will light up heat for some period of time, shut off all but induction motor before reaching temperature and then continue to run induction motor without relighting burners. Shutting switch off for several minutes then on will light and repeat this process. Please advise.
Expert:  airheatman replied 1 year ago.

Not sure what to check after all of this.I will open to see if other experts have ideas.

Expert:  Phil replied 1 year ago.

Hello,

I need to be sure if you replaced the printed circuit board or not.

If you did not replace it, then that is the most likely problem. 98% chance.

If you replace the printed circuit board, then I am out of ideas along with the previous expert.

Let me know about all that in very explicit terms, we can go from there.

Customer: replied 1 year ago.
What I replaced was the white Rodgers control 50e47-070 that's in the box in front of the blower motor. Is this what you're referring to?
Customer: replied 1 year ago.
Also, can the flame sensor fail rather than just be dirty? If so, wouldn't that exhibit these symptoms or no?
Expert:  Phil replied 1 year ago.

Thanks... you replaced the ignition module, on some furnaces that suffices for the printed circuit card... if there is no other item with over 10 wires connected to it, then yes, that is what I was talking about when discussing the printed circuit card.

The flame sensor is just a stainless steel rod.. with an insulated base. The ignition module puts 24 volts AC into the rod, then the burner flame acts to draw off the positive aspects of the 24vac ...leaving 24volt DC in its place, which then flows back to the ignition module as 2 to 5 micro amps DC When the ignition module senses that 2 to 5 micro amps, it allows power to the gas valve.

If the flame goes out, the 2 to 5 micro amp flow ceases, and the ignition control module turns power to the gas valve off.

Causes for flame sensor failure, is a bad ground at the metal burner head, so that the 24vac current cannot flow through the flame... thus not returning a 24vold DC signal to the ignition control.

A dirty flame sensor rod will not leak 24vac into the flame.. so will fail as a flame sensor, (requires cleaning)

There is about a 10% chance at this point that you have a 'reverse polarity' issue. You may have watch this video a few times to get the concepts completely understood.

https://www.youtube.com/watch?v=XfAPkJVYUpY

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip-icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions.

We can go from there.

Customer: replied 1 year ago.
Attached are photos of the wiring diagrams.I've also noticed that below the black fan that hooks up to the PVC intake, there is a small amount of standing water. I also enclosed a picture of this. Thought that may be related to whatever's going on.
Customer: replied 1 year ago.
From the looks of it the water is able to contact a ground, 2 plastic connectors and fall down by the circuit board/ignition module
Expert:  Phil replied 1 year ago.

Hello again, the furnace is in trouble from a number of different directions and not something that any home owner should try to tackle themselves.

If you can tell me which direction you are from the center of the nearest city I can probably locate a short list well rate HVAC shops that will look it over and give you an estimate on repairs.

I can opt out after that so that other of our experts here can take a look at your question, that will be pretty much of a long shot however.

Customer: replied 1 year ago.
I have a couple I can call. However it seems to me like the water leak either from a hose or induction motor would cause the short cycling condition of water contacted electrical components, wouldn't it?The issue with fuses and hot surface igniter was separate and resolved, there was a short that has been located and repaired.