No Heat On York Diamond 80 Gas Furnace


Old 10-01-06, 05:37 AM
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No Heat On York Diamond 80 Gas Furnace

Here is the situation: I have no heat when on Auto mode. When on Fan mode, I can hear and feel Cold Air come out of vent.

When I troubleshoot my system as mentioned on several post here in this forum, here is what happens:

Turn machine on:

Motor starts to hum
No ignition/No spark/No flame
I do not hear the high pitch noise that sounds like a flame/heat blower.

Is this a simple fix or should I get a repairman?

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Old 10-01-06, 07:10 AM
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When you said motor hums . Id call a tech to check it for sure.

Old 01-12-08, 05:23 PM
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Thumbs up cold air

this reply is much later than the original message but may help others doing research.

about three days ago i woke up to hear the furnace running, however it was pushing only cold air. i have a york furnace which was in the home when i bought it about a year ago, the house was built in 03. i went to check the diagnostic led and it gave me four blinks which meant the limit switch was open. i did a ton of research since i knew almost nothing about furnaces and i'm not the type to pay some shmuck 300 bucks for an hour and a 20 peice. so i finally located the limit switch, which i'm pretty sure my furnace only had the one (since some have more than one). through my research i found sometimes these stick open when they are activated, so when i removed it i rapped on it a little and replaced it into the furnace. i did this several times and it would allow the firing cycle to complete maybe two times.

the limit switch is a safety device which shuts down the furnace when the plenum (i think thats the right terminology) air gets too hot after it goes through the heat source (in my case its right after the three gas burners). this can be caused by not enough air flow past the burners. so i checked the return air ducts, opened all the registers, and checked my filters, and i even removed one of them to completely rule it out.

then i contacted a heating retailer to get a new limit switch, luckily it was only 18 bucks for a new one. i swapped out the switches and the first run started normal. as i finally felt some relief the damn furnace went out again. because of my schedule i went another day without the heat (which sucks in alaska).

then i throught maybe the contacts on the limit switch are too loose, so i clamped them a little and still nothing. i called a friend of mine who knows a little about a lot to get another pair of eyes to look at it. on his way over i decided to clean up the area a little and vaccuum some junk out from inside the furnace compartment. as i was moving the wires around i noticed a lot of clicking, like circuits were being made and lost in the circuit board. i messed with it a little more and found that if i moved the plug on the bottom left (the one with 6-7 wires going into it) it would make that clicking noise again and if i found the sweet spot, the blinking led would stop and the furnace would start up normal. after checking some wires with the volt meter, we decided it was something to do with the board itself. so we unplugged everything and inspected the board. after looking at the back of the board, we didnt see any broken tracks. what we did see is a dime size yellow spot, like there was some shorting going on in that area.

I called the heating store and they had me bring down the circuit board (which you'll need to do since there are so many different ones), and a new one was 155 bucks, not bad for a new brain. the guy at the store said the yellow spot pretty much ruins the circuit board and it would think there was something wrong with the furnace when just the circuits were bad on the board. so i went home and put in the new circuit board and it worked perfectly.

it took about five hours for the house to warm up since it was below zero outside.

long story short, if your getting cold air without any blockages, and replacing the part doesnt work, it's probably the frickin circuit board.
Old 01-12-08, 05:33 PM
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You're to be commended for all the research/reading done on your own.

And for braving the Alaskan subfreezing temperatures without heat. Man! it must be tough!

Thanks for the long and interesting story, spiced with good sense of humor; I have not laughed this much in awhile.
Old 01-13-08, 08:04 PM
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Sorry I didn't see this sooner

A couple of months ago, I had exactly the same probelm. After all of the guy shere guided me through checking everything, I finally called my service company. The service tech checked everything that I had done with no solution. He then told me he was making an educated guess that the control module was bad. He said he had seen this same situation a number of times on the York Diamond 80's. He was correct and replaced the control module and everyting fired.Fooling with the heater and learning things about gas heaters(this was my first one) was interesting and I have since replaced the blower motor, the inducer motor and the igniter so that everything is now new. One stretch without heat convinced me that sometimes, more than normal service and cleaning is necessary,lol.

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