It’s been warm for the past few weeks in SoCal, and I turned the thermostat off a while ago. But there’s a weather system coming in this weekend that’s going to cool things down, and it was chilly in the house this morning. I turned the thermostat back on, and nothing happened. I checked the fuse, and it’s fine, the switch seems to be on. I’ve determined that there is no power getting to the power switch (which feeds the fuse, which feeds the furnace electronics). No breakers are tripped, and I don’t know which breaker it’s on. Any ideas? If it’s actually failed wiring, that could be nightmare to trace/repair.
[Saturday-afternoon update]
Welp, checked all the breakers, and they all have voltage at the output.
[Sunday-morning update]
Thanks for all the advice in comments. I suspect I’m going to have to kill power to the house, and try to do an RF trace (and hope it comes through the armor). Fortunately, it’s not really an emergency. The temp in the house was 64F when we woke up this morning, and while it will be a cool couple of days until this cutoff low with rain passes through, it will be heating up later this week. Worst case is sweaters and a heavier bed covering, until I figure it out.
You mention the breakers are not tripped. Are you sure? Worth cycling them off and on again to verify. Take the time to figure out what each one feeds and write it down, you will spend some time but never have to scratch your head in the dark again. You can buy a voltage detector at well-supplied hardware stores like Lowes or Home Depot, put the tip near a wire or insert the plastic tip into a receptacle slot and if it’s hot (120V present) it will flash / beep at you.
It’s very unlikely that a wire has just broken (unless you have old aluminum wiring). Any recent construction work that might allow a nail to pierce a cable or otherwise?
Any recent construction work that might allow a nail to pierce a cable or otherwise?
Unfortunately, yes. I may have to get on the general contractor’s ass.
There should be a breaker for the furnace. Flip it off and back on. Sometimes they pop and it can be hard to tell.
There very well could be, but I have no clue which one it is.
Bridge the thermostat contacts in the furnace and see what happens. I suspect a bad thermostat.
a) The connection from the thermostat is closed (and when I turn it off, it’s open)
b) There IS NO POWER TO THE FURNACE.
I have identified the problem with the furnace. What I don’t know is why it has no power.
I had the same problem a few months ago. The problem turned out to be a component inside the switch which had failed from years of cycling back and forth. Take a look at power into and power *past* the components and that might track it down.
There is no power coming into the switch. And it almost never gets opened and closed.
Little known fact: All breakers are only guaranteed to trip once, then the warranty is void. We think of them as switches, but the manufacturer has no way of knowing how severe the surge was that caused one to trip, so no guarantees after that.
Check to make sure your breakers are seated properly in your main panel. Check the voltage at each breaker to ensure you are getting 120.
Be extra sure you have your “Red Emergency Switch” on. I had the same problem, had a HVAC guy come out, he flipped the switch to on and charged me $40. Not sure who shut it off. But I won’t make that mistake again.
I have no “red emergency switch,” AFAIK. There is a master power switch, which feeds a fuse, which feeds the circuit board. There is no voltage entering it.
The furnace should be on a double breaker (50 amp) unless it is a really small furnace. Typically a dryer, electric stove, ac and furnace will be on double breakers so you could throw these one at a time and see if you get it back.
It could be that the breaker itself has failed. I replaced one for a friend just a few months ago so they do wear out. The long slog would be to test the breakers at the box and see if you have power flowing from each of them.
It’s a gas furnace, 15 amp. Only double breaker I have is one I installed for a spa.
Well, that makes for a harder find. At least you can test all the breakers on the house side and see if any are not providing current. That might be the best way to find this.
That’s my next step, probably. We’ve had the house for a quarter of a century, and I’ve never really mapped the breakers, so I should just bite the bullet and do that this weekend.
Until voltage at the output of the circuit breaker is measured we can’t be sure there isn’t a problem with the circuit breaker itself. But if there was construction work along a plausible routing for the wiring, that’s also a reasonable suspect.
Rand, with power on the downstream side of the breakers, and not at the furnace, that means a circuit break somewhere.
My #1 suspect would be the outlet the furnace plugs in at, usually inconveniently located behind the furnace. A loose wire from thermal motion is commonplace in outlets like that.
#2 suspect, a line break due to either damage from construction, or, if you have aluminum wiring, a broken core.
The good news is it’s easy to trace with the right equipment. What I’ve used in similar situations is a RF (radio frequency) tracer. What it does it feed radio frequency charges into the line (basically making the line a low level radio transmitter antenna). You then can, from up to a couple of feet from the line, detect whether you have continuity at various points along its path. You’d need to test both the line and neutral cores.
When I needed a RF tracer, I was able to find one at a local equipment rental place, for $20. It found my problem (loose connection in a junction box).
The furnace is (fortunately) in the same utility room as the breaker box. It is fed by an armored cable with 14 gauge wire. I can trace it to where it disappears into the wall a few feet from the box, but I’ll have to open up the wall there to see what happens to it after that. Also, will an RF tracer work through armored cable?
Try tightening the lock screw for the wire to ensure it isn’t corrosion causing a high resistance on the contact…or since it is in the same room grab an old extension cord and run a temporary line over to see if it really is the wire from the box.
Will an RF trace work through BX cable – probably not very well but at least you can try. If the cable’s good you will see the signal at the other end. Very unlikely that BX would suffer a break mid-length in a short run through the wall though.
Next step is to open the covers, shine a light and look for loose wires. You’ve opened the switch box for the furnace and not found voltage anywhere inside, so find the other end of the furnace wire in your breaker panel. If you can’t identify it from the jacketing then you might want to consider a tone injector. Hopefully there is only one wire per breaker. Don’t forget as was mentioned to verify that the neutrals are all screwed down tight.
I’ll also second the suggestion to stick a new 15A breaker in your panel (if there is there room for more?) and run a temporary feed to the furnace supply switch. Sometimes old breakers do fail, I had to replace a 10 year old one recently. Or you could do a real quick & dirty test and use a cheater cord. Screw Marrettes on the old wires in the switch box to insulate them in case they start to work again. No idea of the California electrical code so you might need to use BX again for this but it’s a pain to work with compared to Romex.
The tracker signal from the wires should couple into the armor conduit like a transformer. Unless the armor is grounded at both ends the signal should then appear, somewhat weakened, on the outside of the armor.
Except that doesn’t let you know a conductor is broken inside ….
Armor is typically grounded at both ends.
I should add that there has been no construction activity anywhere near this area. And I’m pretty sure it’s copper.
Is the break box by any chance within a jumper-cable length of the furnace?
Rand,I had to have the motherboard on our 17 year old furnace replaced in Febuary, as the tech explained the vibration can eventually break the solder. Might want to look at that.
Once again, what part of THERE IS NO VOLTAGE COMING INTO THE FURNACE do people not understand?
https://www.harborfreight.com/cable-tracker-94181.html
$25. I have one, it works. Make DAMN sure the breaker is off on the line you’re tracing – prefereably popped right out of the panel. Or lift the line itself from the breaker-box terminal. (Only way to disconnect it if you’re tracing a neutral.)
Hook up the transmitter to the wire you want to trace, switch the xmitter on, follow the wire through the wall by sweeping the tracer probe back and forth and noting where the tone is strongest – and where it stops. If the hot wire shows continuous, try the neutral next.
It’s a bit fiddly and “touch” dependent, but to avoid opening an entire wall for $25, more than worth the effort. (Practice on something simple like an unplugged extension cord first to get a feel for it.)
When you’ve ID’d where the discontinuity is, then it’s time to start digging into the wall, fun fun fun.
If you’re SURE power is off at the furnace, you can also trace back from that end. Be careful!
What part of I DO NOT KNOW WHAT BREAKER IT IS ON do you people not understand?
Some of us handy types sort of take FINDING OUT WHICH FRIGGING BREAKER IT’S ON as so fundamental it’s not worth endlessly repeating.
And if you’d read my post to the end, you’d have seen one way how, even with one wire apparently discontinuous. There are others. Given the box and the furnace in the same room, a continuty tester or ohm meter with one long lead comes to mind.
Now, if you want to be safe, while you’re still targeting multiple breakers, depending on the trace method you may want to pull power from thwe whole box. Be organized about it (tools *and* light) and it should be only a few minutes.
Whoops! Some weirdness with your comment software there; the first try didn’t show even with a page reload till I’d posted the second.
Just got back from six weeks and 6100 highway miles of family emergency, so forgive the acerb. But ID that breaker.
One quick question. Were you checking the voltage at the furnace from the hot to the frame or some other ground, or to the neutral wire?
There’s a possibility your hot is fine but your neutral has come loose, which, if you’re checking hot to neutral at the furnace end, will show up as zero volts.
But my guess is that you’re not doing that, and that AC voltage is not getting to your furnace.
Thus my inquiry as to whether you’re in jumper cable distance, or have a spare 12 or 14 gauge wire you could just run from your breaker box to your furnace, even if you have to hold one end. You could just pick any random breaker to run on the separate wire, and the worst that could happen is that it will trip, along with some other appliance in the house.
Well, actually the worst that could happen involves a gas explosion and some kind of freak electrical surge that takes out most of the US power grid, but I mean, what are the odds of that? We’ll just blame it on Russian hackers and move on.
You could also pick up another 15-amp breaker that’s compatible with your breaker box, along with a sufficient length of AC wiring (located in the store next to the breakers), install the new breaker, and use your old furnace wire as the pull wire for your new wiring.
By yanking pretty hard you should be able to identify which breaker the old wire was on. You may identify the problem just getting started in this process, but if not, you’ll be replacing the wiring and using a new breaker to feed the furnace. If you get into trouble, such as the old wire being so bound up somewhere that you can’t identify it by yanking, then as a temporary measure to get the house warm, you could just wire up the new breaker, throw the new wire across the floor, and land it in your furnace.
I know it can get frustrating. I’ve got a 12-gauge wire run from my breaker box, across the floor to an outlet, which is back feeding my bedroom. I’ll remove the wire when I move out, because the alternative is crawling around in the attic for a week, checking wires run in the 1920’s and 1970’s, and knowing that the original wiring is u-nailed to the studs and joists, in a house with plaster and lathe walls. Also, my house was wired either by a schizophrenic or Pablo Picasso. I’m not sure which. I’m pretty sure the basement wiring was done by some kind of giant spider. I can’t even figure out what some of it was ever for.
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I checked against both neutral and ground.
Rand, I work for a heating company and I would redirect you to the earlier comment about the furnace switch being off. I cannot tell you the countless times we have sent a tech to a “no heat” only to find that the switch was off.
Naturally, the switch is between the breaker and the unit. Sometimes there are more than one, in series. Local requirements and builder’s prejudice decide where they go. Normally, there is one some safe distance away from the unit, so it can be turned off without risk. If there is a second one, it is normally right next to the unit so repairmen can turn it on and off easily while working a problem. Normally, there is a red switch plate over it, with writing, but many don’t like the looks so they replace it with a normal switch plate as soon as the building inspector is gone.
Yes, this means the wire would lead out of the panel and out of the utility room all the way to some mystery switch, then back to the furnace, so a big loop in and out of your utility room. And it certainly explains no power to the unit.
So, look for some mystery light switch somewhere that you never noticed, usually up higher than a light switch, but not always. Top of the basement stairs is usual, if the utility room is in the basement. If on the first floor, it could be outside the utility room or down the hall. The usual requirement is that the switch be someplace you can exit from safely. I have never heard of one being outside in a weather box, but wouldn’t entirely rule it out. Might check around by your AC compressor.
You are not describing anything in my house (e.g., we have no a/c). There are no red switches, and there are no “mystery switches.” There is no basement, and the furnace is in a closet in the laundry room on the ground floor, the same room in which the breaker box is. I think you’re assuming this is an electric, high-power furnace. It is not. It’s a 110V 15A circuit to feed fans, and a circuit board that controls them and the burners. There is no more need for an “emergency switch” on it than on any other gas appliance.
Rand, I’m not sure if an RF trace will work in armored cable; the RF may well use the armor as a waveguide – that could make finding the actual break location difficult, though might be workable if you play with the frequency a bit. (I’ve never tried it on armored, so I am only guessing) On the other hand, I’d be highly surprised if the cable had broken within the armor.
You’ve mentioned that you don’t know which breaker it’s on, so IMHO finding that out is job#1, and then testing it to make sure you have 120v and sufficient amp capacity on the downstream side. My preferred method of testing a suspect breaker is check it for voltage and amps (put a load like a toaster in series) and then, to be doubly sure, swap it for an identical known-good breaker in the panel.
To find the breaker (which should be a dedicated 15 amp) a process of elimination is one method (and I suggest doing it; breakers should all be labeled for both convenience and safety) or trace the wiring visually in the back of the panel (unless I’m misreading you, the armored cable goes into the box directly). so it should be easy.
And… are you certain that the breaker for that line is in that box and not just routed through it? The reason I ask is I’ve seen, occasionally, homes with more than one breaker box. For example, the breaker for a mailbox light is sometimes outside near the meter, in the box just below the meter. I’ve seen other things added there as well – though they should not be.
Best of luck…
BTW, when working on the box (or anything!), make sure you double check that the power is actually off to it; I’ve seen, once, a cutoff switch miswired into the neutral side, so the box was very much live from power to ground. That’s why I always check for power between live and ground, live and neutral, and neutral and ground – I won’t trust my life to the assumption that it is wired correctly.
AFAIK, it’s the only breaker box in the house, other than the main breaker in the front of the lot, and a GFI that I installed in the rear for a spa. I’ve had this house for a quarter of a century, I’d have found things like other breakers and mystery switches long ago if they existed. The house was built forty years ago, so I wouldn’t necessarily bet that the furnace is on a dedicated circuit, but I’m not aware of anything else that’s not working. But of course, all the breakers are showing voltage on the output.
As far as seeing armor coming into the box, I’d have to open drywall around the box to do that. Which it may come to.
Hrmmm… your mention of GFI and also the possibility of a non-dedicated line got me to thinking… that furnace is in a laundry room, so, maybe, just maybe, there’s a GFCI involved? Or said another way, are you 100% certain there isn’t? Houses of that era tended not to have them, but… perhaps as a later addition. If so, a common means of wiring them is to have a GFCI as the first outlet on a line, with other outlets slaved to it. Those chained outlets downstream will likely have no indication they are GFI protected.
So, my suggestion ( it’s an easy one to do) is to take a nightlight or some other small electrical plug in thing and check every prime GFCI outlet you have (most often found in bathrooms and laundry rooms), and then press the test switch on it, then the reset, then check again. It’s important to test them before and cycling the test/reset so you know if something changed.
Best of luck. I don’t envy you; diagnostics is often the hardest part of any electrical or automotive DIY repair job.
There is a GFI outlet in the box. Everything on it is currently functional…
The only other GFI outlets are what I’ve installed, or the recent electricians upgrading our bathrooms have installed. Hard to see how that would affect the furnace circuit.
As we discussed, the furnace circuit should be dedicated to one breaker. Did the furnace work after the electricians did their changes? Again a remote chance that the power could be on a branch circuit that they left un-connected in an outlet box or is on a now-tripped GFI – but you’d know about that in your bathroom.
I”m looking forward to hearing the solution, here’s hoping it doesn’t take too long.
Arizona CJ has given you great advice throughout this thread. Not much more to add.
The other thing that I hesitate to mention is that sometimes they wire in a “summer fan” switch to allow circulating air without the furnace itself running. If there is such a switch and it’s wired wrong, it could be disconnecting your power. Unlikely but grasping at threads here.
If you cared to share some pictures of the guts of the various boxes we might be able to help more. Stay warm this week!
If I want to run just the fan, there’s a switch on the thermostat to do that. It doesn’t work, either. Because no power.
Just a thought, but is there any chance your furnace is powered by green energy, specifically wind power, solar, and unicorns running in giant hamster wheels?
It could well be that your wiring is fine but you’re connected to a grid based on insane lunacy and climate delusions. If so, I suggest you burn what firewood or US currency you can.to keep warm, and then move inland till you encounter people with actual fuels that can provide heat.
Admittedly this wasn’t helpful troubleshooting advice, but it is perhaps useful life trajectory advice. In the heartland you will be warm, even it’s from burning the bodies of anfifa activists. Nobody would bat an eye until you sell the house.