Gas and Oil Home Heating Furnaces - York Furnace won't start

It's probably a 1992 model as the house was built then.

When I press the safety switch, the inducer blower starts right away, then the ignitor starts to glow red hot. But the gas valve won't open. Actually, there is not voltage at the gas valve. In a minute or so, the ingitor shuts off with a click. At the same time the gas valve gets about 25V for 2 seconds. The led is not on. Then the sequence repeats...

Gas supply should not be a problem as there is another unit(goodman) standing side by side and is working. Could it be the control module, the relays, or something else? Any help would be greatly appreciated.

Sounds like a bad ignition control module. Since the HSI gets hot, the next step should be applying power to turn on the gas valve. Since that doesn't happen, the control module must be bad.

This is also my hunch. But is there anything I can further test to make sure? What do the brown relays do?

You don't test components on an ignition control. The ignition control is a "black box." It's not designed to be tested or repaired.

If certain inputs are present, the ignition control should do certain things. If it does those things, it's good. If it doesn't, it's bad.

In your case, the pressure switch closes, turning on the hot surface igniter for a period of time, and then it should turn on the power to open the main gas valve. Since it's not doing that, the ignition control is bad.


Maybe someone else will suggest something to test. But it seems preetty conclusive to me.

( Someone is BOUND to make a fool out of me for that one!)

Can you swap parts from the other Goodman, to test?

I haven't checked if the Goodman parts work on a York. I kind of doubt. I will see.

Sorry, I forgot the one you are inquiring about is a York. But check it out, as you said. But they would both have to have HSI's, for there to be a chance.

I asked this because I read an old post. The person didn't give the exact symptom of the problem. But he said he fixed it by replacing the brown relays. I don't know what the relays do and how to test them... I guess I just try to learn a bit more.

I will probably order a control module and give it a try. Thanks a lot for the responses!

It's not the control module. I ordered a new one and put it on. It's still doing the same thing. Any other ideas?

Did you try to test between one of the gas valve terminals and a metal ground, rather than between 2 gas valve terminals?, to see if you get similar results?

It's possible that something about your gas valve or wiring, that you are actually testing in series through a coil(resistor) in the gas valve. I have already been thrown curve balls on gas valve readings myself, as I have had various results with different furnaces. I'd try that, just in case the opposite is ocuring with volts, and that you really HAVE 24 volts to the gas valve, but then loose it 2 seconds after the ignitor shuts off, rather than the other way around, as you say. In series testing causes voltages to do the complete opposite. (I.e. ever try testing across the terminal of a light switch that works? You get 0 volts. But you will get 120 volts from either terminal to ground when the switch is on.)

Then let's say you really DID have 24 volts to the gas valve after all. Then it could be that you have a weak ignitor!!(this does happen...really! They often slowly burn through and the ohms increases and the glow is not as hot any more...not enough to set off the gas).

The ignitor should glow more of a real yellow-white that you can't hardly look at without going blind. You can ohms test it, to confirm likely good or bad.

Or, if that's not it, you could have a stuck gas valve that you maybe could confirm by rapping on it with the butt end of a screwdriver durign HSI peak glow.

When I press the safety switch, the inducer blower starts right away, then the ignitor starts to glow red hot. But the gas valve won't open. Actually, there is not voltage at the gas valve. In a minute or so, the ingitor shuts off with a click. At the same time the gas valve gets about 25V for 2 seconds. The led is not on. Then the sequence repeats...




After the igniter has 20-30 seconds or so to heat up, you should get 24 VAC applied to the gas valve which should cause the gas to turn on. If the burners don't light, the gas valve would typically remain energized for 3-5 seconds and then shut off.

You say there is no voltage to the gas valve, but then say you do get voltage for 2 seconds or so. Perhaps you can describe this more clearly and in greater detail.





It's not exactly clear what you are describing above.

SeattlePioneer:
I think we are essentially saying the same thing. The gas valve does not get power WHEN it's supposed to - as you said, 20 - 30 seconds after the ignitor is on. But I did see some kind of "power surge" there when the ignitor is shutting off. Again, here is the sequence of events I observed. Hope it's more clear.

1. Press the safety switch
2. Inducer motor starts right away
3. HSI starts to glow in a few seconds and stays white hot for about 40 seconds (It's an estimate. I didn't time it). No power at the gas valve during this 40 seconds or so.
4. HSI turns off with a click sound. At the same time the multimeter at the gas valve terminals gets 25VAC for about 2 seconds. It goes away before the reading is stable.


ecman51`:
The wiring is very unlikely the problem as it worked last season and nobody touched it. The ignitor looks good to me. It gets white hot very quick. Actually, it's less than one year old. I changed it last year.

Your description of the operation seems pretty clear.

Other than ecman's suggestion of a wiring defect, I can't think of any cause of that kind of erratic operation other than a bad ignition control.

The brief voltage at the gas valve & the "click" make me wonder if gas valve is failing to open despite the power being applied. The timing of the voltage loss & HSI shutting down seems to be about right for "trial for ignition".

For safety sake shut off the gas as the line valve. Use a long screwdriver or rod by placing one end against the gas valve & the other against your ear then put the furnace thru an ignition sequence. If you hear/feel a click from the valve it's possible the solenoid is working but the valve is failing to open.

The gas valve solenoid itself could be shorting out and drawing away all the 24 volts. And that is why you are not getting a voltage reading on your resistance multimeter, as the 24vac current is taking the easiest path to ground rather than thru the the solenoid first (or your test meter).

I happened to think of what I am going to say, from what another poster did on another thread I read today: He jumpered to the gas valve, to rule on if there is a voltage supply issue. You could try that after the ignitor has been glowing white hot, as you say, for 30 seconds. This would just be a brief test. Make sure not to do it before ignitor glowing full force; otherwise you could get a delayed ignition in your face!

BTW, I have had to replace HSI's in a year. Due to the possible expense of a gas valve, I would not let a simple test for that go by the wayside.

I will check the ignitor and gas valve as suggested when I am home Friday. But before that I still have one question from the beginning. Together with the control module, there are two general purpose relays and a capacitor at the bottom. Can anyone tell what they are for? I am just trying to learn. Thanks a lot for all the help so far!

Ignition controls aren't intended to be repaired, and manufacturers therefore usually don't provide schematic diagrams of them.

They are properly treated as black boxes that either work or don't work and are replaced if they don't.

This is also my hunch. But is there anything I can further test to make sure? What do the brown relays do?

Unhook 2 wires going to gas valve

using 2 jumper wires

hook 1 jumper wire to 1 meter lead other end to 1 wire you pulled off gas valve


hook other wire to other wire you took off gas valve

push in safety switch hold , after ind. motor starts ,hsi glows see if you get 24 volts sooner , if you do , bad gas valve

Ignition controls aren't intended to be repaired, and manufacturers therefore usually don't provide schematic diagrams of them.

They are properly treated as black boxes that either work or don't work and are replaced if they don't.
Now I kind of realized what you are talking about. You think the control module and the relays are just one "blackbox". To me they seem to be separate things. I wish there was an easy way for me to post a picture so that you know what I meant.

Tried a few things:

1. unplugged the wires to the gas valve and connected them directly to the multimeter. everything was the same - 25VAC came for 2 seconds when the ignitor is turning off. There was a click sound at the moment. I did do the screwdriver test as suggested by Grady: attach one end to the gas valve and the other to my ear. I couldn't tell the click was from the gas valve. I was pretty loud though.

2. Did the same test on the Goodman - unplugged the wires to the gas valve and attached them to the multimeter. At the moment the safety switch was pressed, there was 13.6VAC on the gas valve wires. After the the ignitor was on for about 30 seconds, it then got 25VAC for about 5 seconds. Then it shuts off as the gas valve was disconnected. Well, it's a Goodman and may have a different design...

3. Checked the ignitor again. It gets about 66 ohms - looks normal to me.

4. double checked the wiring to the new control module again as the new one is a 50E47-843, while the old one is 50E47-070. Everything looked okay. The led turns yellow for 2 seconds for a self check and then becomes solid green - normal operation.

The HSI is good.

The click and 25 volts, only as the HSI is shutting down, sounds to me like the ignition module is shot, IMO.

Maybe the reason is the HSI circuit is shorting to the gas valve circuit, in the ignition module, and will only work AFTER the HSI circuit is OPEN.

Whatever those relays are, I do not suspect they have anything to do with this sequence. That should be totally contained in the ignition module. Maybe they could be a blower fan timer or sequencer or inducer relay.

The easiest way to post pictures here is to open a free account at photobucket.com, post the pix there, & provide a link to them here.

Whatever those relays are, I do not suspect they have anything to do with this sequence. That should be totally contained in the ignition module. Maybe they could be a blower fan timer or sequencer or inducer relay.

According to the last post of this thread (http://forum.doityourself.com/archive/index.php/t-375785.html), the relays can be the cause of ignition problem.

I read it. He popped in and said he had ALMOST the same symptoms. Someone who does not know furnaces might not realize that "almost" does not help an accurate diagnosis. If one thing is different in the sequence, that person's "almost" will almost certainly have a different cause. He might not have had 'ignition'. But then again, maybe his inducer did not even work, while yours does. If his inducer say did not even work first, he'd have a totally different cause. Possibly a relay in his case. But because he did not get specific - who knows.

If the parts are as cheap as he said, go ahead and change them, then.

I agree with ecman. Long experience on this mboard suggests it's a waste of time for people to hunt through old posts hoping to find a case the same as their own.

People are just kidding themselves with that kind of diagnostic method in most cases.

Update:

After running out of ideas, I called a technican in. He watched the cycle a few times and then concluded that it was the flame sensor. He explained that it was because he didn't see voltage on the flame sensor. After a little while, he wanted to check the thermostat and told me that the thermostat was broken with more confidence. He said there was no 24v for heat, even though there was power for AC and the fan. I happen to have a spare one of the same kind. He put it on and checked that it did have 24V for heat. He turned it on with fingers crossed. Unfortunately, the symptom remained the same.

Has anyone actually checked to see if there is any gas coming out of the gas valve?

He put it on and checked that it did have 24V for heat. He turned it on with fingers crossed. Unfortunately, the symptom remained the same.

What did he do? Shrug his shoulders and say he hasn't a clue, and leave?

What did he do? Shrug his shoulders and say he hasn't a clue, and leave?
He did make a suggestion before he left: try a new gas valve, and if it still doesn't work, cut the wires and throw the furnace out the window ;-(

I take it he was too afraid that a gas valve might not be it either, so he is leaving that to someone else to take the fall for any possible misdiagnosis.

He did make a suggestion before he left: try a new gas valve, and if it still doesn't work, cut the wires and throw the furnace out the window ;-(


Never contradict the repairman who is on site.

Has anyone actually checked to see if there is any gas coming out of the gas valve?


There are a lot of things I'd have done to test out this furnace.

Applying power directly to the gas valve to verify that it's working and that gas flows when it's energized. Disconnecting the gas valve and other parts as needed to verify something odd isn't happening.

Bypassing safeties for the same reason.

This kind of forum is way too clumsy to be of much help on obscure, difficult to diagnose problems, especially when the person on the other end is a DIYer with limited skills you don't want to try tests only an experienced repairman should do.

Unfortunately, the repairman who inspected the furnace had no luck diagnosing the problem either.

Frankly, I think I'm done here. The best thing is to call in another repairman with better diagnostic skills. Perhaps a call to the repair service who sent the first guy out can produce a person with those skills.

And I'd be glad to hear what the problem turns out to be.

Sorry I can't do more.

Frankly, I think I'm done here. The best thing is to call in another repairman with better diagnostic skills. Perhaps a call to the repair service who sent the first guy out can produce a person with those skills.

And I'd be glad to hear what the problem turns out to be.

Sorry I can't do more.

I concur with S/P & believe the best place to start is with a call to the service company. If they don't have a more skilled servicer, it's time to call someone else. Friends, neighbors, co-workers, etc. are all possible sources of service company recommendations. Don't feel shy about asking.