My ducane furnace wont satisfy the thermostat. when I turn up the heat the burner runs for about a minute, blows out, all the while the fan motor continues to run. when i pull the switch board cover, it blinks 3 times. says that the pressure switch is the problem. I have put 4 pressure switches on this furnace in 3 years. is this just a cheaply made part? or is there other problems causing the 3 blinks(faulty pressure switch)?
A short cycle heat cycle indicat a pressure switch replacement was needed. This did not fix the problem. the problem was in PCV line since the end was filled with slugs and cause the line to backup with water. When this happen the system would stop asking for gas. the water would leak out and it would restart. The problem was fixed by cleaning value at end of PCV. This released the water, two quart of water, that was back up causing problem. Curious if a filter change indicator was providing a clue that was missed?
The high limit switch on the exhaust fan is bad. Ducane has a replacement part but your contractor has to call them to get it. I am a contractor and found the problem first as ducane techs told me.
Check that there is not a small piece of trash getting into the tube for the pressure switch.
Also check that the evaporator us not plugged full of dirt and dust from an improperly installed or poorly maintenanced filter.
This will cause burner short cycling and inability to warm the space.
Reply what you find and I'll give further instruction.
Look for where the 2 copper pipes come into the side of the unit. That is the evaporator. The plastic line that I think you are speaking of is the condensate line, where water drains during A/C operation. That's the bottom of the evap.
Hard to get to, no matter where it is. But, it's a mighty good filter when the filter isn't properly installed or leaks.
You have described the classic symptoms of a dirty evaporator, or collapsed, closed off ductwork. Maybe a fan running too slow, but rarely that.
There won't be much if any water in the condensate line in the winter. The cold dry air absorbs most of it, ( and when you heat the air, it absorbs it even faster).
So no, water won't be freezing in the condensate line right now, and the condensate line is so far away from the pressure switch I think your talking about, it shouldn't have any impact anyway. The pressure switch only proves to the control board the inducer fan is running before it turns the gas valve on.
So yes, "A" coil it is (another term for evaporator).. And downflows are usually easier to clean. You should be able to get get the front panel off the A coil case, and reach inside to pull out what is now a blanket of dried dirt/duct/lint/hair. If the coil is a slab, there will only be one surface to clean. If it's an A coil, there will be two.
You'll be surprised next summer how much better your A/C is going to work, especially if no one has jacked around with the refirgerant charge.
I wouldn't worry too much about cleaning the coil, though. It will clean itself next summer when the A/C is used. At least don't worry about it if you can pull the blanket of stuff off, and don't see embedded dirt clogging the coil. Be sure and have all you noce white things away from the supply air grills when you start the uniti back up, becuase there is going to be some dust blowing when you first start the fan up. And to minimize cleaning later on, flipt the Fan switch on the thermostat to ON, for a short time (thats the same fan speed as the A?C uses.).
Oops, my bad. You've got one of those really efficient 90+ furnaces.
Still, same result though. It's not ever cold enough in there to freezer water to plug anything up unless you loose power for 2-3 days at below freezing temperatures.
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I am somewhat familiar with my furnace, but where is the evaporator?
I have found dirt in the past in the 2" rubber coupling that connects to the PVC line. cleaning this out worked for a short time. this is a vacation home.we leave the heat on 45 all winter, but when i turn up the stat, it comes right on. then the issue i listed before happens.
Ah, the evaporator is the A coil!
we had filter cloth at one point in the registers for dust , i removed them and the furnace seemed to work fine for about 2 months. I figured the cloth was creating to much static pressure in the duct system. All the sudden the 3 blink problem started to occur again.
With this cold weather, if the condensate line gets some ice in it, could it make the pressure switch seem as if its the problem?
could this be creating the effect of a dirty evaporater? ice closing up the condensate line?
If in fact its a dirty evaporater, do i need to take the furnace off the A Coil(down flow unit) and clean it?
I agree with everything you are saying except, i have a good bit of water coming out of the condensate line(not like when the A/C is running) but a good bit of water comes through my condensate line in the winter. Remember, this is a high efficientcy furnace.it has a sealed trap. a 5/8" line comes off the induser and 2 small lines coming off the pressure switch that drop into the sealed trap. when i walk outside, there is a steady drip running out of the condensate line.again, not like in the summer, but water is steadily coming out.
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