Having troubles with my furnace. It's a York diamond 80, model number P3DNA12N06401A. A few weeks ago it started getting cold enough to need heat WeWent to fire it up and it was fine for the first day or so then it was just blowing cold air. I am now getting 8 flashes from the circuit board. I have replaced the flame sensor, the hot surface ignitor, and most recently the control board. When first turning on it ignites and stays running for a few minutes, then shuts off and tries to reignite a few seconds after. The inducer fan just continues to run even after system faults itself out with the 8 flashes. I ha e checked the pressure switch and seems to be properly working. I did pull off the tube and give it a good blow in and out just to clear it out.I waswas assuming the control board was the issue. A few of the traces on the back side look to be burnt. Well it's doing the same thing after replacing. Is there anything you guys can think of that may cause it to cycle like this? Thanks in advance for any help. It's going on two weeks without heat and the Queen of the house is not happy. I don't want to call a pro in until I have tried everything possible.

 

Hey Jake, Rule #1: Keep the Queen happy. We will find some info on your furnace and get back to you.

 

Thank you very much if there is any info I didn't provide please let me know. Kind of bummed that I have about $250 into it now and it's doing the same as it was. The 8 flashes is indicating a lockout due to no flame. That makes me think an issue with the flame sensor but it's brand new.

 

Another question, is the blower motor supposed to kick on as soon as heat is called for? I could have sworn that previously the inducer motor would kick on then the ignitor, then Gas, followed lastly by the blower motor. But now as soon as the furnace kicks on the blower is starting and not shutting off and the same with the inducer. I have to kill the power to get them off.

 

Yes, the last thing to come on should be the blower.

 

Can you post a close up pic of the wiring diagram? I'm am not having any luck finding anything on that model. PJmax or Houston will probably stop by tonight, maybe they can helps us.

 

Do you see any flash codes on the control board before it finally locks out? From your description of the symptoms it sounds like you may have an open limit switch. Have you checked to see if your air filter is clean and/or your a/c evaporator coil is not clogged.

 

I have the air filter out right now have tried with it in and out, no difference. The flashing light only comes on after its locked out, nothing while it cycles. I have not checked the evap coil as I'm not too sure how to access it. It's on the bottom of the unit and has no access panel. And once I figure out how to post pics I can do a pic of the wiring. Thanks guys

 

I also tried to bypass the rollout switch above the burner and that didn't help. And I also get full air out of the vents, not sure if that helps any.

 

Have also noticed the flames go out fast like they would when I pinch off the pressure switch.

 

Have you tested the high limit switch (see attached photo). I suggest you turn off power to the furnace, remove the two wires from the switch terminals and then join them together using a paper clip or jumper wire. Then restore power and see if furnace will operate. Only use this as a test for a short period.

 

My brother and I have just narrowed it down to that switch. We think that is the cause. As redneck as it sounds I took a leaf blower to the evap coil area and fired it back up. It is still cycling off but it has been running got 20 mins now and seems to be way better. We will check the switch though. Thanks again!

 

Here is the way the limit switch looks from the other side. I suggest you turn off power, remove the wires from the terminals and check the switch for continuity. If there is no continuity, you can remove the limit switch (two screws) and gently tap on the bi-metal disc with a butter knife to see if it will re-set. Then re-install it and it may get you by until you can get the replacement part. Don;t forget, the limit switch is a safety device and will open because there is an over-temp condition. Never bypass a safety device!!

 

We have the switch bypassed and it is still cycling off. Ran for about 4 or 5 mins then flame stopped. Would having both access doors off cause any issues?

 

You should be getting a flash code on the control board that points toward the problem. Also, the fact that it shuts down after 4-5 minutes sounds like a flame sensor issue. You stated you replaced both the control board and the flame sensor and it did not correct your issue. A common mistake people make when replacing the flame sensor is not positioning the sensor in the correct location and the flame does not engulf it properly causing problems. I suggest you check the flame sensor position.

 

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It's difficult to say for sure from the photo, but it appears the flame sensor is on the outer edge of the flame but probably alright.

 

Is there anyway to adjust it. I just assumed that you line the holes up and screw it down. I also assumed if the flame sensor was bad it wouldn't run for 4 to 5 mins at a time. Just the recent go around with it has my house upto 78 degrees. It just won't stay running Lol. It wants to but something is causing it to test my last nerve

 

Yes, troubleshooting furnaces can be extremely frustrating at times. The flame sensor position is probably alright.

 

There is only one more switch that I know of and it's inside the blower motor. I can not reach because the exhaust tubing runs right in front of the opening. Could that be the culprit?

 

Is it inside the blower motor or on top of the blower motor area? I would definitely try to reach it and try for a reset. Can you remove the wires from the terminals to bypass it for testing purposes?

 

It's inside the motor, I can't get to the wires at the switch but I should be able to trace them back and jump them there. We had to reset it one time before but I can't recall why. It is a pain though. There is a tube inside a tube and no easy way to remove. I think we had to take out the inducer motor and drop the inside tube down the bottom to pull out the outer one. I know for a fact the blower is running. Like an idiot I tried reaching the reset before it had finished spinning. It has to be something simple. I was almost certain it was the high limit switch but sure enough it makes me feel like an ass once more.

 

This is a pic of the wires and as far in as I could reach.

 

On some furnaces, when the blower continues to run it is because a limit is open. The auxiliary limit switch may very well be the culprit. Some Diamond 80 furnaces have two auxiliary limits.
In the photo you posted, is that not the reset button I circled in white and the leads on either side?

 

Well darn after looking at the pic, the switch is right there lol. Didn't even notice that. I'mtthinking with a mirror, a flashlight, and a coat hanger I might be able to trip it. Alls I know is thank God for space heaters. Thanks for all your help so far

 

This stupid pipe is not helping my issues Lol. Arm is too big to go in from the right and if only I had two elbows the left side would be fine.

 

That pipe won't slide up out of the way a foot or two? That is a difficult space to access.

 

No because the hot exhaust pipe is inside that one and it will not budge. I think it's attached to the inducer and can't remember if we had to completely take out the inducer motor or wha. HHopefully today I can get it going. Thanks so much for all your knowledge and input.

 

That is unfortunate. Of course, we have no idea how the vent pipe is configured. Hopefully, you can get it.

 

Ok I was able to get to the switch andrreset it as far as I know. I pushed the center inaand out a few times. It is still kicking off. On a cold start it will run longer than after it faults out and I reset it. Wonder if there is another limit switch that I am missing or something. I am so ungodly boggled right now. I can't mess with it for hours each day just to get it to reach my desired temp. Thinking I should just replace the damn thing.

 

A limit switch opens because of an over temperature condition. I suggest you check the vent pipe at the exit point to ensure there is nothing blocking it such as a bird's nest or other obstruction. As stated earlier, a dirty/clogged evaporator coil will restrict the air flow and cause an overheat condition.

 

The a coil was somewhat dirty but not horrible. And I don't believe it's the exhaust vent because I unhooked it at the top of the furnace and ran it for a short time and still kicked off. I hooked the vent back up as I know that is not safe to breath it but I didn't have a ladder at the time to reach the roof so that was my only other option. Is there a proper way to clean the a coil? I took the leaf blower to it on high but dunno that it removed much of anything. Once again thanks for all your time and knowledge!

 

I feel like you would've saved a lot of time and money by calling someone. Stop taking a leaf blower to the coil...that's doing nothing.

 

I'm not so sure what a pro would do that we haven't. We have verified we are getting correct voltages everywhere and everything is working in correct order. I thinkI just have a switch getting tripped from an over heating issue, is there a proper waytto clean the coil with the limited space to work with. The leaf blower was used to blow anything out that may have been loose.

 

Is your furnace an up flow or down flow?

 

If up flow, buy a can of coil cleaner, I believe Home Depot sold it at one point. Take the cover off the front of the coil, then there will be a metal piece in the middle of the "A" in the coil. There should be a few screws holding that metal piece in place. Once you remove it you will be able to see the bottom of the coil. If it's dirty use that foam coil cleaner and a wire brush or tooth brush and go with the fins. That should do the trick if that's the problem. I'm not trying to be a dick but you have put a lot of time and money into this. I guess at least you got some experience and knowledge for next time at minimum.

 

Sorry to triple post but also make sure all registers are open and no returns are covered or blocked.

 

It is a down flow with just one large cold air return at the top. I appreciate the helpI ddidn't think you were bring a dick. And I'm not trying to be either. I don't know what else I can try but I feel if I call in a pro it will be just to replace the unit. We have had issues with it every year since we have lived here. Just not as bad as this time. But I can't see spending the money for him to do all the stuff I have spent the last few days doing. Guess I could just have it checked and see what they think and an estimate to fix it. I'd I do need it replaced hopefully I can have it moved to the attached garage. We have a manufactured modular home and the furnace is located in a small closet in the hallway right next to the living room so when heat or air is running it's fairly loud. And having the large return duct right above the door doesn't help with the noise.

 

Here is a picture of the coil. It's not a great view but it don't seemed to be clogged. Definitely some dirt but I get strong air from the vents so I wouldn't think that would be causing the shut downs. Was trying to see if the leaf blower would remove the surface debris