Since past 2 days, I am busting my head resolving my York diamond 80 heat furnace issue. The furnace is not blowing hot air and the error code LED blinks 4 times, which corresponds to an issue with Open high limit switch. Well, there are tons of videos floating around to resolve this issue. Apparently the fix is supposed to be simple…well, not so much. I tried every thing from cleaning the flame sensor, by passing the high limit switch (by short circuiting via wire) and checking up all vents and filters. The issue remains. Here’s the current behavior of the furnace.
1-Turn on the furnace.
2-Small induction motor starts running…but right away LED start blinking 4 times (Open high limit switch)…hence igniter doesn’t kick in and no flames therefore. Motor continues to run.
3-By pass the high limit switch by connecting the two wire via small jump cable and restart.
4-This time there are no LED blinks. Igniter kick in, turns red hot, gas start blowing in and flames comes up just fine .
5-Flames remains running for next couple of minutes. All of a sudden I hear a click and flames goes off.
6-Reset everything again but the LED still blinks 4 times even with the limit switch by pass but the igniter remains cold. This behavior remains as of now.
It is also important to note that sometimes resetting two switches on the main blower panel (Which I believe are some pressure switches) and 3 on the igniter panel would make the igniter to heat up, but this behavior is random. My most recent tries still does work, and LED keeps on blinking indicating issue with open switch.
Guys please help me out here. As mentioned earlier, I tried every thing from cleaning the flame sensor, by passing the high limit switch (by short circuiting via wire) and checking up all vents and filters. Will greatly help for further debug help.