York Diamond 90 - Symptoms of dead control board?

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Old 02-06-10, 05:04 PM
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Exclamation York Diamond 90 - Symptoms of dead control board?

My furnace has been locking out with 8 flashes for the past few months. The sequence progressed normally and the burners would ignite, but then flare out soon after (most of the time). I had the pressure checked at the main line coming into the house as well as at the furnace (just before the gas valve) and ruled that out as a possible cause. I had been putting off getting it fixed by just manually clearing the code a few times (powering off and on the furnace) to bring the house up to temperature as needed. That was until last night anyway..

That's when it finally gave out on me completely and now it won't initiate the ignition sequence at all. I'm getting a solid red LED (mostly solid, it does flicker every couple of seconds, but definitely doesn't flash) that I can no longer clear by cycling the power. At first I was ready to chalk it up to a bad gas valve and started to make calls to get it replaced, but after troubleshooting it myself most of the day I'm starting to suspect the control board instead.

The main reason I'm ready to blame the control board is that the error code displays immediately without any indication of starting the ignition sequence, and the code itself will not clear no matter what I try. While I was poking around trying to troubleshoot, I took out the flame sensor and gave it a much needed cleaning, which now I think may have been the real culprit of the original 8 flash flame loss. Only problem is I don't have any way of knowing that now since I can't get the ignition sequence kicked off!

I found a replacement board online, but I don't want to shell out the $200 for it until I'm fairly confident that it will fix the issue. I've read a few other threads about people who have tried replacing their control boards and still ended up having the same problem as before. I haven't seen any posts about what the true symptoms of a dead control board are though, so I'm hoping someone will be able to confirm my rationale or offer alternative suggestions.

The good news is I have other ways of heating *most* of my house (gas fireplace and electric baseboard) but I'm hoping to at least place an order for the parts in the next few days.

Any help/advice would be greatly appreciated.
 
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Old 02-07-10, 07:20 AM
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I was ready to shout flame sensor until I kept reading. Your furnace manual, or the back of the front cover to the furnace, top or bottom should have a chart telling you what the continuous red flash means. Although it could be a flame rollout switch if it is resettable with some red button in the middle. It sits near the front, next to the burners.
 
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Old 02-07-10, 11:19 AM
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The furnace I just worked on (a Ruud) was locked out, so there was not even a hum -totally dead), and I found as a tipoff that when I felt the inducer motor, it was very warm-hot. I tried to turn the fanblade attached to the motor itself(not the fanblade that vents the furnace), with a pointy tool I slipped in through the end slots of the motor, and it was seized. That is why there was no sequence, just like you.

First check you furnace and make sure not safety reset buttons are tripped. Carefully look at where any small device is that has wires attached, for a resettable button or pin, and push and listen/feel if little click - if so that means it was tripped and now reset. ["ender" already mentioned these]

Also, unplug multiple pin jack connectors (often a milky white plastic connector that can have up to 12 pins inside that plug into their female counterparts). I have often found failures attributed to this. Inspect for water leakeage onto such connectors or boards(from the ac above, or backed up or leaking condensate connections). You can unplug, even slightly helps, then replug on spades to ensure good contact.

Also make sure you do not have a board that has a replaceable 3 amp fuse on it that may have blown, or circuit breaker.

You need to have 120 volts to the furnace.

Then you have to have 120 volts pass through the interlock door switch located on the inside of the blower door. You need to see if you are getting 120 volts to it, and through it, when you push in the button by hand. Then you have to make sure when you put the blower door back on that the blower door can depress the switch properly.

Then you have to have 24 volts from the transformer. That 24 volts has to make it's way through the stat. But you can bypass the stat by jumpering the R and W thermostat wires in the furnace, and see if that makes it run.

You have to make sure that you have 24 volts and/or 120 volts at the board and get 120 volts to the inducer. A relay is involved in bridging contacts in a relay (often located on the board now, unfortunately, rather than a separate replaceable part, the way they used to be) so that the 24 volt stat current gets switched to 120v needed for the inducer fan to run.

If you have a 3-wire pressure switch(as opposed to a typical 2-wire pressure switch), the furnace will not make a sound if the pressure switch got stuck closed in the normally open (NO) position after the last working sequence of the furnace when it ran the last time. For 3-wire pressure swithes to work, the NC to C connection on the switch part attached to the diaphram, must be made("closed"). You can test with a voltmeter from each terminal to a good sheetmetal or screw ground. If one terminal of the same device has power and the other does not, that means the switch is open. ALL safety switch device are to be "closed" to make the furnace work.

Also you need to see if even 24 volts is incoming to the pressure switch.

If it isn't then you have to trace back to and test the limit switch to see if 24 volt power is even getting to it.
 
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Old 02-08-10, 03:20 PM
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First off, thank you both for your quick and helpful responses. I'll save you having to read all the gory details below (unless you're interested) and quickly sum up where I'm at right now. For peace of mind and in hopes of a faster resolution, I made an appointment for a repair technician to diagnose the problem this morning. After an hour of troubleshooting he determined that despite his initial doubts, he was ready to blame the control board as well and recommended I get it replaced. He did reserve the right to be wrong though and said that there's still a possibility that something else is going on. The good news is it only cost me $30 to get the second opinion.

Before he came though I did go through mostly everything you both suggested and here's what I found:

ender - The manual has two entries that could describe what I'm seeing.. "Continuous Flash" and "Steady On". Between the two it is definitely more of a "Steady On" because even though it does flicker slightly, it definitely does not flash on/off repeatedly which is what I would expect from a "Continuous Flash". "Steady On" indicates:

"This fault occurs if the gas valve is energized when there is no call for heat. If this happens the vent motor is energized and will remain energized for 5 seconds or until the fault clears itself at which point the vent motor de-energizes. This failure is counted as a recycle. Check the gas valve and control for proper operation."

while "Continuous Flash" is:

"This indicates that flame was sensed when there was not a call for heat. With this fault code the control will turn on
both the inducer motor and supply air blower. A gas valve that leaks through or is slow closing would typically cause this fault."

Prior to describing the flash codes, the troubleshooting section also reads:

"The control continuously monitors its own operation and the operation of the system. If a failure occurs, the LED will indicate the failure code. If the failure is internal to the control, the light will stay on continuously. In this case, the entire control should be replaced, as the control is not field repairable."

I've actually removed both the gas valve and flame sensor connections from the circuited board and I still see the error same error condition appear immediately. That, along with the fact that the code never tries to clear or reset as the typical error codes do lead me to think that it is an issue internal to the control board.

I located the reset on the flame rollout switch, but it wasn't tripped so no luck there.

ecman - I didn't notice it at first, but there is definitely an audible hum when I depress the door switch and allow power to the control board. However, I can't really tell if it's just the transformer or a seized motor trying to turn, although it definitely sounds like is is coming from the blower compartment as opposed to the inducer. The transformer sits right on top of the blower though so that doesn't tell me much, and I can easily and freely move the blower fan blades with my hand. And my inducer is definitely not warm or hot, which makes sense because the control board doesn't seem to be energizing it anyway (more below).

I could only find one obvious safety switch, and that was on the rollout switch that ender pointed to. However, it wasn't tripped.

I had already tried disconnecting and re-connecting the wiring harnesses too. Definitely no signs of any water in the area or any other obvious damage or dirty pins or connectors. I had already checked the 3A fuse visually too, but I confirmed that it was not blown using a voltmeter as well.

I verified that I have 120v and 24v at both the transformer and control board. 120v through the door switch, and the door definitely depresses the switch when it's in place. I traced the 24V from the transformer through the fuse and into both the R and W stat connections. I tried jumping R and W anyway, but still no difference.

Here's where I lose it - I have pretty much nothing (< 3V) going into the inducer motor. Now I'm thinking that's just because the board is failing before even making the call to power the motor, but I'm not sure how that works exactly. Or, if the relay on the board is failing, it would make sense that I'd be getting nothing at the inducer right? I haven't had a chance to try to pinpoint where on the board this is happening, but that's my best guess at the moment.

The pressure switch is only a 2-wire, does not appear to be stuck and is getting 24V.

So I'm planning to bite the bullet and buy the board replacement, but if you've made it this far and still think I should check something else first I'm still open to suggestion.

Thanks again! I'll post the resolution as soon as I can so hopefully someone else will benefit from this thread someday too.
 
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Old 02-08-10, 04:27 PM
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Originally Posted by brrrYD90 View Post
First off, thank you both for your quick and helpful responses.

And my inducer is definitely not warm or hot, which makes sense because the control board doesn't seem to be energizing it anyway (more below).

Here's where I lose it - I have pretty much nothing (< 3V) going into the inducer motor. Now I'm thinking that's just because the board is failing before even making the call to power the motor, but I'm not sure how that works exactly. Or, if the relay on the board is failing, it would make sense that I'd be getting nothing at the inducer right?
On newer furnaces with control boards, often the relay for the inducer is on the control board. That relay takes the 24 volts that goes through the thermostat at a call for heat, to then energize the 120 volt circuit, in order to make the inducer come on. Sounds like that is where it is getting lost.

You can't just go and have a relay put on those boards. Some backyward experimenter/mechanic-type may try to run around finding such a relay, and try his luck - but no pro will do this. For one thing, the boards today are likely coated with a rosin, and the solder is buried beneath a nice thick layer of that. Then trying to find that relay might prove difficult.
 
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Old 03-18-10, 08:43 AM
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Problem Solved!

I've been meaning to update this thread for a while now but just haven't gotten around to it. Long story short, the problem was indeed the control board, and the furnace came back to life after swapping in the replacement.

All told the repair only cost me $120, but the biggest downside was that it took a total of 11 days to resolve (most of that due to a late UPS shipment)! Once I got the new board though it was smooth sailing and only about 45 minutes worth of work to swap it in. The technician quoted me anywhere between $600-$800, so a little DIY went a long way for sure!

Cost breakdown:
Unfortunately I am still having issues with flame loss (cleaning the flame sensor didn't help after all..) and getting lockouts with 8 (but sometimes 6) flashes. I'll probably just start a new thread for that issue though, as I still need to troubleshoot a bit further.

Thanks again for all of the help and advice ecman and ender!
 
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Old 03-18-10, 02:19 PM
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You can keep the same thread because that way all the history is here, and your OP made it out to be the furnace is not working right - and it still isn't!

What ignites your furnace again? And when the flame goes out, what flame are you talking about(a pilot or main burners?). And how long after you get flame, does it go out? Is that time frame fairly consistant, or does it vary? When the flame goes out does the inducer go out also, or does that keep running? What kind of stat do you have, and have you replaced it (if so, when, in relation to problems you have been having?)? The info can maybe help determine if stat is shutting off, or if you have a furnace venting issue, or a low voltage safety issue like it high limits, for example.)
 
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Old 03-22-10, 03:11 PM
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Fair enough!

It's a pilot-less system. The ignition mechanism is a coil (for lack of a better term) that heats up and glows red until the gas ignites. So the flame I was referring to is from the main burners. The length of time definitely varies - sometimes within a minute or two, other times it just works. It seems like the colder it is outside, the faster it fails, although that's just based on general observation really.

The inducer doesn't cut out right away either. It stays on and blows cold air for a bit before shutting down completely (after 4 total losses).

Haven't replaced the stat at all, but I just recently bought the place so I'm not sure what the full history is.. I'm also traveling at the moment and don't recall the manufacturer, but I'll find out and update the thread later this week.

I thought venting might be an issue too, so I tried loosening the burner compartment cover to let more air through that way. That didn't work, so I removed the cover completely (I know that probably isn't the best idea!) and ran it that way for a bit. The interesting thing there is it definitely has an effect, meaning that it takes a lot longer for the flame to go out, but it still does fail eventually in the same manner. So I don't know if that means the issue is being compounded by poor ventilation as well.

I found this thread which describes the exact same problem I'm having, but unfortunately there was never any resolution other than cleaning the flame sensor, which I've already ruled out (link is from google cache as the actual thread seems to be down):

Problem with my York Diamond 90 - http://www.hvacmechanic.com/ Forums
 
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Old 03-25-10, 12:57 PM
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The thermostat is a LuxPro. I didn't check the model number on it, but it looks identical to this one:

LuxProProducts

I actually do want to get a new thermostat anyway because this one isn't programmable. I haven't begun looking for a new one yet, but if it could be contributing to the flame loss I can start shopping around for a replacement. Worst case it will at least rule it out as a possible cause...

To be honest though I have my doubts that its being caused by the stat. Or I should say, it doesn't really seem symptomatic of the stat continuously calling for and canceling the heat. Is there an easy way to test for proper gas valve operation? I mentioned earlier that I've had the pressure tested going into the furnace and it looked good, but if the valve isn't opening all the way or is cutting off the flow I would expect this kind of behavior.

The other thing I'm not clear on is the function of the pressure switch. Most of the time the failure code indicates that the flame was lost 5 times, but every now and then I do get the 6 flash error code which indicates "the pressure switch opened 4 times during the call for heat." I'm assuming that the pressure switch is some sort of fail-safe to prevent gas leaks/explosions but I'm not really sure. Could it be cutting off the gas flow? Is there any way to (temporarily) bypass the pressure valve and test to see if the furnace operates normally?
 
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Old 03-26-10, 03:57 PM
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You can bypass the pressure switch, temporarily by joining the incoming and outgoing wire, if you are dealing with only a 2-wire pressure switch, or you'd have to jumper between NO and C on a 3-wire pressure switch.

To see if the stat is causing flame on and off, you can use a voltmeter where the low voltage power strip is in your furnace. AC volt test from the W terminal to C, (or to the metal of the furnace, instead of C). If you have 24 volts the stat is ON, and if the volts go away, the stat is now shut off.

The inducer also indicates what the stat is doing. If the inducer continues to run, even if the flame goes out, chances are the stat is still on. And if the flame AND inducer go off simultaneously, the stat is likely off.
 
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