Fye on my Foul-Functioning FUBAR Furnace!

Just be thankful it isn't one of the defective furnaces mfd by Consolidated back in that same time period (1983 to 1992 or something like that) under a bunch of different brands. Those like to catch fire eventually and burn down your house, caused by overheating & cracking of metal parts in the burner area. York wasn't on the list of impacted brands, though.

Unfortunately, mine was. Had to rip the damn thing out and have it replaced or they were going to turn off the gas (not that I would have kept using once we knew).

John

Tell me about it, a lot of homes up in LA/OC have those too.
 
The possibility of cracks in the heat exchanger are why I keep a functioning Carbon Monoxide detector in the house. I think should be mandatory in houses with gas heat.
 
The possibility of cracks in the heat exchanger are why I keep a functioning Carbon Monoxide detector in the house. I think should be mandatory in houses with gas heat.

They are here in California, and I bought some a couple of months ago. had our house appraised for a refi and the appraiser said where are the CO detectors? My wife grabbed one of the four still in the package - the appraiser said "I need a picture of one plugged in to get approval". Must've worked as we signed the papers last Tuesday.

Very useful to have and they can save lives.
 
Well that pressure switch finally came in Friday and I put it in on the weekend. It was so warm it wasn't till this morning that I got a chance to try it. No dice - didn't even start up like it has been first thing in the morning with the old switch. So I called the furnace guy back and let him have at it. Oh well, it was a $37 gamble, not much considering the alternatives.

I do have a CO detector, because of the woodstove, and it's located fairly close to both of them.
 
If all the switches are closed, gas pressure and gas valve checks ok then I would look at the control board: aging Relays and caps. Same problems as an old amp.
 
IME the pressure switches are a safety that indicates something else is wrong and won't let the controller go to the next step. The few problems we've had were almost always related to an obstruction in the vent pipes. Even though I thought the pipes were clear, the controller was always right.

Is there a light on the control board that tells the status of the furnace? Ours is the same era and the light is steady when OK, but blinks a certain number of times if there's a fault. Then you know where to look for a solution. Watching and listening to the furnace start and go through all it's steps is kind of fascinating to me.
 
If all the switches are closed, gas pressure and gas valve checks ok then I would look at the control board: aging Relays and caps. Same problems as an old amp.

I'm starting to think that...read on...

IME the pressure switches are a safety that indicates something else is wrong and won't let the controller go to the next step. The few problems we've had were almost always related to an obstruction in the vent pipes. Even though I thought the pipes were clear, the controller was always right.

Is there a light on the control board that tells the status of the furnace? Ours is the same era and the light is steady when OK, but blinks a certain number of times if there's a fault. Then you know where to look for a solution. Watching and listening to the furnace start and go through all it's steps is kind of fascinating to me.

The guy came out today for the third time, and the damn thing WOULD NOT MALFUNCTION for him. Actually it did to begin with, and he determined that my NEW pressure switch was faulty. It was not switching even at considerably higher vacuum than its rating. So he put the old one back in. It fired up, and continued to do so over and over. I told him on the phone (I was at work, wife was there) that it will start up after it's been sitting a long time, but fail on the second cycle almost every time. He could not replicate it.

I'm thinking maybe a control board component too. This thing is from 1989, no indicator lights or error codes. The controller has a big can cap on it, which I've already pulled and checked - it's OK on capacitance, and I cleaned the contacts. I think it's a motor cap for the air handler. I'll see if I can find a schematic for the rest of the thing, or try to open it up and look at components. It's just a box with terminals on the outside so I have no idea what's in it, other than the big cap on the outside. But its symptoms could be consistent with some component malfunctioning when it's warm (after it just ran) but not when it's been cold for awhile. Like a wonky transistor, relay, resistor etc. :scratch2:
 
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hmmm... older furnace, might be able to find another control box inexpensively?
 
I'm going to look for that, but it's quite tedious searching online parts houses, some of their search engines are better than others!
 
If all looks good and clean and you can follow the sequence of firing---Exhaust fan on--ignitor glows--gas valve opens--burner ignition----air handler starts and runs through cycle, your problem is probably on the board. You can jumper and bypass most of the limit switches to eliminate them as a cause.

You also want to make sure that your condensate piping and discharge hose has a good clean path. Sometimes, when the exhaust fan is doing it's thing and some crud is in the line, the blower fan, when it starts, will pull just enough vacuum around the exhaust fan to trip the pressure hold down switch.

Fixing these older furnaces can be an inefficient economic situation compared to buying new. If you have an HVAC buddy, he should be able to get you a new unit for less than a grand. I have a 100K BTU 94% Janitrol that cost me $700, wholesale (that was a few years ago). The problem is that even if you get it all operating, there is no guarantee that the fire box or condensing unit will not rust through immediately. Up here, the new utility mantra is 0 PPM CO with their sniffer. Your CO detector is around 40 PPM to avert nuisance alarms.
 
Does the pilot valve open even though the ignitor doesn't glow? You can test this with a lighter stick. My guess is no and if so, the safety systems are working as designed. If the pilot flame lights without the glow rod operating then I would suspect that relay etc.

You say there are 2 pressure switches, is the other normally open or closed? Does it test normal? Is it on the negative pressure side?

Is the condensate switch a pressure or vacuum switch? What is its function? i.e. is it there to ensure exhaust flow doesn't blow back though the drain? If the pressure switch isn't closing/opening with the exhaust blower running does it run consistently with the switch bypassed?

A bad exchanger would likely show a fault after full ignition and heat up. Maybe.

That's all I got.
 
Update on this so I don't leave it hanging. A big thank you to everyone - the furnace is running for now!

The pressure switch I had put in a few days earlier, turned out was not working. First furnace guy, on his 3d visit, tested it and found it was not opening at >2" vacuum pressure. Supposed to be rated at 1.13". So I fought with the vendor and got a replacement. He put the old one back in and the furnace worked for him.

About 12/23 the other half called another repair co. without saying she was going to. I was at work, so this guy shows up and guess what, the furnace would not malfunction for him either. I talked to him on the phone and he agreed I was down to the controller board at this point.

I had already ordered a board, which came in 2 hours after the guy was there. I woulda had him come later and install it, but did not know he was coming. :-\ But we were leaving town for xmas, so I quick put the board in after work before leaving, and the furnace still didn't work. We left heaters on and the weather was warm. Got back on the 29th and it was 62 in the house, not bad.

I had also ordered a relay off that board that I thought was bad, but the board got there first.

After talking with my FIL (life-long HVAC guy) I had a few things to try when I got back. I unhooked the air intake pipe at the furnace and cut into it about 4 ft. from the end so as to pull out a section with a bunch of elbows that were inaccessible from outside the house. Blew it out with the vacuum cleaner, no bird nests. Lo and behold, the furnace worked consistently with it unhooked. It draws mostly room air (I kinda have it partially off the fitting so as to draw at least some outside air) so it wastes a bit of heat but it runs.

Either there is some other clog in that 25 ft. of pipe, 20 ft. of which I vacuumed out in the fall, OR...the new inducer fan I put on is actually a bit too weak and does not draw enough air to run the furnace properly. It was supposed to be a correct replacement and looked/fit correct. This could explain why the pressure switch was not opening, if the fan doesn't draw enough vacuum. I think. What I'm not sure about is why it works sometimes. Might be wind against the house helping the intake sometimes, or there is a bird nest I can't see that flips up and down sometimes and blocks the air flow.

Soon as the weather clears a bit I'm going to get my leaf blower out of storage and blow out that 20 ft of inaccessible pipe good and hard. If that doesn't find anything I was thinking of putting a T and valve on the intake line near the furnace so I can bleed in enough room air to make it run.

I don't think the furnace has too many seasons left in it, the heat exch will probably rust out soon. I've spent about $500 in parts and labor so I'm not chucking it now!
 
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Elbows do add restriction. It it is my heater, A brute force add on blower to force intake air flow. It may not be another relay, depending on the rating of what is on controller. Probably a inexpansive small fan in line / on the intake will work. It will save you the room air and give you time to trouble shoot.
 
IMO your FIL is on the right track. I had a wasp nest caught in an elbow that would flip 90deg in the pipe and sometimes block, sometimes not.

Here's a way to clean the pipe. Put a vacuum cleaner hose on one end and turn it on. Get enough string to run the length of the pipe and tie a small piece of TP or tissue to the end. With the vacuum running, feed the end with the TP into the pipe. The vacuum will suck the paper through, pulling the string with it. Once you get the string all the way through, you can attach a stronger cord or rope to it and pull that through if needed. Then tie something big enough to pull through the pipe without getting stuck, like a chunk of soft foam rubber or a sock, to the end and pull that through the pipe. It should clear out anything in the pipe at no cost.
 
Great idea Jimbo, thanks. I was just going to blow it hard with a leaf blower, but mud daubers will be attached of course, so it might not dislodge everything. There are two elbows in line even if I remove that funky section next to the furnace (which has 2 more).

I thought of the extra fan, what would you use for that? And how to control it so it turns on only when the main fan is on. Sounded like a headache but if there is an easy way...
 
-snip-
The pressure switch I had put in a few days earlier, turned out was not working. First furnace guy, on his 3d visit, tested it and found it was not opening at >2" vacuum pressure. Supposed to be rated at 1.13". So I fought with the vendor and got a replacement.--snip

And, this is why I won't take parts back at work!
Glad to hear your furnace is working! :D
 
I had a blockage in one of the pipes ( can't remember which) And I took some fishing line and attached a small kids hard plastic ball about 2" in diameter by drilling a hole completely through it. Then, I took my shop vac outside and attached it to each pipe one at a time. I went inside and fed the ball with fishing line attached to it as it got sucked up the pipe. It cleared some leaves and grass that a mouse somehow got into the pipe.

I attached the string in case the ball did not make it all the way through and I would have to pull it back. You do need a good 2 HP or so Shop Vac and duct tape it to the outside pipe. The plastic ball was about 1/4" to 3/8" smaller in diameter than the inside of the pipe.

Just a thought.
 
Some great ideas in cleaning the intake pipes. Should try that first.

I would pull a fan from an old kitchen range hood (Cheap from thrift shop) or a bath room ceiling exhaust fan and have it blowing into the intake. It should be easy to put it on outside wall. The main blower relay can trip another relay or just parallel new relay to the main will run the fan. If the main relay is beefy enough, I will just parallel the fan to the blower.
 
Great idea Jimbo, thanks. I was just going to blow it hard with a leaf blower, but mud daubers will be attached of course, so it might not dislodge everything. There are two elbows in line even if I remove that funky section next to the furnace (which has 2 more).

I thought of the extra fan, what would you use for that? And how to control it so it turns on only when the main fan is on. Sounded like a headache but if there is an easy way...

Give up the fan idea. :nono: You'll just be fooling the safety feature (pressure switch) into ignoring a problem that it's telling you about. Think replacing a fuse with a larger one.:thumbsdn: Additionally, that switch will need to go back to the opposite mode at some point in the cycle to continue the cycle or it will shut down.

BTW I did a little searching on your furnace. AFAICT it's 92% efficient. The best furnaces today are 97%. You won't really notice much savings, especially if you're heating with wood by going to a new one.
 
Give up the fan idea. :nono: You'll just be fooling the safety feature (pressure switch) into ignoring a problem that it's telling you about. Think replacing a fuse with a larger one.:thumbsdn: Additionally, that switch will need to go back to the opposite mode at some point in the cycle to continue the cycle or it will shut down.

BTW I did a little searching on your furnace. AFAICT it's 92% efficient. The best furnaces today are 97%. You won't really notice much savings, especially if you're heating with wood by going to a new one.

Thanks, good to know. I kinda figured that but was not sure what the efficiencies were at this point.

My FIL has an old hanging gas heater for his garage. Says it's built like a tank, he pulled it out of some building and it just runs. He says it's 80% efficient, though. We've come a long way!
 
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