Water Heater Won't Start

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SpeedThrills

SpeedThrills

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It's old, but if it's a simple fix, that'd be great.
A couple months ago, it wasn't as hot as it should've been, but it came around and has been okay until today. The pilot is lit, and the exhaust fan runs (until I unplug it), but the burner won't light. I've lightly tapped the gas valve. Nothing. (It has an exhaust fan because the exhaust stack is horizontal.)
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SpeedThrills said:
It's old, but if it's a simple fix, that'd be great.
A couple months ago, it wasn't as hot as it should've been, but it came around and has been okay until today. The pilot is lit, and the exhaust fan runs (until I unplug it), but the burner won't light. I've lightly tapped the gas valve. Nothing. (It has an exhaust fan because the exhaust stack is horizontal.)
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Make sure the pressure switch hose and orifices are clear. They can get clogged with debris not allowing the switch to close when the fan is running.
 
It’s 6 months shy of being 20 years old; well into bonus time. Do you have a drain nearby for when it does leak? When do plan on replacing it?
 
I assume it does not try to light? Without a wiring diagram I can offer few suggestions. Most fan drafted tanks do not have a pilot, rather, electronic ignition. It surely must have some sort of fan "prove" switch so that it will not light without proper vent pressure/ suction from the fan. The pilot would not stay lit if the thermocouple was bad or circuit opened
 
EDIT: ARE YOU SURE this has a pilot, or did you happen to look in there as the hot surface ignition device was heating up? (orange glow)

In any case, see if you can post the wiring diagram in a clear manner, even if you have to overlap a couple of photos

BE CAREFUL poking around in there. IF THAT IS a hot surface igniter, they operate off LINE VOLTAGE AKA 120V AC

I used to know WTH I was doing with this stuff. I spent nearly a dozen years servicing, repairing, and even installing HVAC/R
 
67Dart273 said:
I assume it does not try to light? Without a wiring diagram I can offer few suggestions. Most fan drafted tanks do not have a pilot, rather, electronic ignition. It surely must have some sort of fan "prove" switch so that it will not light without proper vent pressure/ suction from the fan. The pilot would not stay lit if the thermocouple was bad or circuit opened
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This is what I was talking about. The pressure switch proves the fan is running. To me it sounds like the fan is constantly running unless he unplugs it. So it's trying to light the main burner but will not until the switch closes.
Causes are debris in orifices at the pressure switch but most likely at the fan itself. The hose could be cracked or a birds nest in the vent itself (happens all the time!)
 
Ok now let's get down to trouble shooting this! It's easy if I'm right in thinking it's a intermittent pilot system which was very common 20 years ago.
First get out your multi meter and set to volts a/c.if you don't have a digital one we are going to be looking for 24v a/c so set your range accordingly.
Now if that fan is running it knows it needs to fire up but can't. You said the pilot was lit. So.

Put one lead to ground (the water line will work or gas line)and check for 24v at both terminals of the pressure switch (sometimes they are called a air proving switch).if you only get voltage on one side of the switch then everything I already said is the culprit. If you get voltage at both terminals then carry on.

If you're water heater is the type I'm thinking the gas valve should have three terminals on it.
MV-main valve
PV-pilot valve
MV/PV-which is the neutral for the two.
Again with your meter one terminal to ground (gas line will obviously be easiest here)the other to PV. This will show 24v because your pilot is lit. I guess that's just for practice haha.
Now ground to MV. If you have 24v at the MV terminal your gas valve is bad. If you don't your ignition control module is bad. If it's an original it's probably a grey box made by Honeywell. Could be black also if it's been changed at some point.
Also I should have mentioned that although we are looking for 24v you won't se it everywhere. It could read 27v or at the valve if it's trying to open but can't it could 12 or 15 or whatever. Hope that makes sense
 
I don't know if this helps, but my buddy had an old camper up at the lake with a propane powered light over the kitchen table. It was always was hard to start. One day he took it apart and looked inside and found a tiny spider web in there, blew it out. It's been working good since.
 
H22A4 said:
It’s 6 months shy of being 20 years old; well into bonus time. Do you have a drain nearby for when it does leak? When do plan on replacing it?
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Def running on borrowed time. Going to be replaced very shortly. I just want to see if it'll run to tide us over.
It's sitting on a drain pan that has a drain hose running into the crawlspace.
67Dart273 said:
EDIT: ARE YOU SURE this has a pilot, or did you happen to look in there as the hot surface ignition device was heating up? (orange glow)

In any case, see if you can post the wiring diagram in a clear manner, even if you have to overlap a couple of photos

BE CAREFUL poking around in there. IF THAT IS a hot surface igniter, they operate off LINE VOLTAGE AKA 120V AC
Click to expand...
Yes, it is a pilot.
pt70 said:
I don't know if this helps, but my buddy had an old camper up at the lake with a propane powered light over the kitchen table. It was always was hard to start. One day he took it apart and looked inside and found a tiny spider web in there, blew it out. It's been working good since.
Click to expand...
I'll check for anything in my skill range.

No luck as to a nest in the stack.

Thanks all. I'm off to check it out...
 
SpeedThrills said:
Def running on borrowed time. Going to be replaced very shortly. I just want to see if it'll run to tide us over.
It's sitting on a drain pan that has a drain hose running into the crawlspace.

Yes, it is a pilot.

I'll check for anything in my skill range.

No luck as to a nest in the stack.

Thanks all. I'm off to check it out...
Click to expand...
I need the wiring diagram to do you any good. I used to work on this stuff, but I need to know what it is that we have
 
My apologies! I typed this about 8:00 and never clicked, "post reply"!!!!!

The hose could be cracked" Bullseye!!! The hose was broken at the motor. As soon as I trimmed it clean and put it on, the burner lit! That would explain why it "kinda" had the problem a couple months ago. It probably wasn't completely broken off then.

Thank you, odie 2882 and 67Dart273!!!

I was told when it was installed, (when the house was built), that the fan was because the stack was horizontal, because they didn't want to run a vertical stack through the roof. From your posts, I see that it is what creates a draft. My only experience invoves units with no fan.

It will get replaced in the very near future. Yes, it's 20 years old and overdue. Now I can do a little research and see what unit to use replace it, and shop around a bit. It's been a long time since I bought one and it looks like I'm in for sticker shock!

I never liked the spaghetti plumbing on it.
 
You REALLY should have stuff like your furnace and water heater serviced periodically. There is debate on how often. AC / furnace once a year. Furnace only, every 2-3 years, or more if you are a neglectful type. And that should include the water tank and any other gas appliances
 
Time for replacement. Usually on a gas heater the thermocouple is bad if it won't light. Like mentioned, are you sure it has a pilot light or electronic ignition? Isee the 115v. rating on the tag. That must be for the fan?
 
67Dart273 said:
You REALLY should have stuff like your furnace and water heater serviced periodically. There is debate on how often. AC / furnace once a year. Furnace only, every 2-3 years, or more if you are a neglectful type. And that should include the water tank and any other gas appliances
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I am definitely guilty of minimal maintenance.

I've flushed the water heater once, and it ran clear. Luckily, never an issue other than last nights.
I clean the reusable filter on the HVAC twice a year. I've had a couple minor issues with it. I've been able to fix them. It's as old as the water heater.
We have a water softener on our well. I clean the injector every couple years. It's always clean. We have city water now, and only use the well for the sprinkler.

My vehicles are maintained to the max. I guess I use the old axiom,"You can sleep in your car, but you can't drive your house".

We built the house when I was about 45. I figured we'll have to replace all major systems (inc. roof) hopefully once. (Water heater, probably more:rolleyes:) It'll be 20 years old when I'm 65. At 85, it'll be my stepdaughter's "investment".
 
SpeedThrills said:
My apologies! I typed this about 8:00 and never clicked, "post reply"!!!!!

The hose could be cracked" Bullseye!!! The hose was broken at the motor. As soon as I trimmed it clean and put it on, the burner lit! That would explain why it "kinda" had the problem a couple months ago. It probably wasn't completely broken off then.

Thank you, odie 2882 and 67Dart273!!!

I was told when it was installed, (when the house was built), that the fan was because the stack was horizontal, because they didn't want to run a vertical stack through the roof. From your posts, I see that it is what creates a draft. My only experience invoves units with no fan.

It will get replaced in the very near future. Yes, it's 20 years old and overdue. Now I can do a little research and see what unit to use replace it, and shop around a bit. It's been a long time since I bought one and it looks like I'm in for sticker shock!

I never liked the spaghetti plumbing on it.
Click to expand...
Glad it was an easy fix for ya! I’ve been a plumber and gas fitter for a little over twenty years and can tell you you are definitely on borrowed time with that heater. But at least now you can phone around and get some quotes on a new unit.
 
odie 2882 said:
Glad it was an easy fix for ya! I’ve been a plumber and gas fitter for a little over twenty years and can tell you you are definitely on borrowed time with that heater. But at least now you can phone around and get some quotes on a new unit.
Click to expand...
I had a good friend (passed) who was a plumber. I picked up just enough to be dangerous!
 
Del was correct. If it was a power burner from the factory, the next thing in sequence is the draft proving switch. A little safety and common sense, these are not hard to work on. The logic is similar for most power ( that's with a fan folks, vs the ones without ) burners. 1. call for heat 2 start the draft fan 3. prove the draft fan is working, usually a end switch AND a draft or similar diaphragm switch.
 
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