Ignition controller flicking at random

[Mouse]

Hi everyone...

I have an extremely old gas water heater. So, I know the first thing a lot of you are going to say is "Replace it", ... Easier said than done since I don't have the cash for that right now. So I'd rather just fix it even if it's just temporary.

Here is what's happening:

1. Turn it on, the HSI (Hot Surface Ignitor) kicks on.
2. The Ignition Control clicks, the gas comes on and we have fire
3. Goes for a random period of time working fine (about 30 secs to 2 minutes)
4. The Ignition Control starts clicking randomly/quickly which turns the gas off and with every click
5. Sometimes when it's done clicking, the gas stays on, sometimes it shuts off.

I made a video of the whole thing if you'd like to see it in action: http://heinleins.com/igcont_irradic.mp4

Steps I have done to try to fix it:

1. Pulled all the plastic tubes that lead to the exhaust fan at the top, washed them, made sure they weren't kinked. (Tried running it without the tubes, nothing worked, which was expected)
2. Made sure nothing was blocking the vent on the outside of the house.
3. No blockage inside the PVC pipe leading to the outside vent.

So, my conclusion is that a part is shot. But, I have no idea what one. Maybe I'm wrong, but nothing has changed on the exterior since the last time I fixed it (the HSI needed to be replaced about 4 months ago)

Any help would be appreciated!

Thank you!
-andy.

 

[Reach4]

I doubt that your WH is extremely old. Pilot lights were the norm for a very long time, and I think they still should be. (The heat from the pilot contributes useful heat IMO.)

A very old water heater would not use a PVC exhaust.

Don't know your heater, but typically there would be something that detects if the flame really started. That may be a thermocouple or some other assembly. Check your documentation for a flame detection replaceable assembly. Alternatively problem could be a sensor looking for air blockage.

Is there an indicator light of some sort? Does it blink? That may be a code.

 

[Sponsor]

 

[Mouse]

I doubt that your WH is extremely old. Pilot lights were the norm for a very long time, and I think they still should be. (The heat from the pilot contributes useful heat IMO.)

A very old water heater would not use a PVC exhaust.

Don't know your heater, but typically there would be something that detects if the flame really started. That may be a thermocouple or some other assembly. Check your documentation for a flame detection replaceable assembly. Alternatively problem could be a sensor looking for air blockage.

Is there an indicator light of some sort? Does it blink? That may be a code.

Thanks for your feedback. I think the heater was installed in/around 1995-1998, so it's up there

There are no lights to check.

I am leaning towards your idea about the sensor that checks for blockage. I am going to assume it's the big round thing that the rubber hose attaches to? This thing:

 

[Reach4]

Does the blower start before ignition is attempted? If so, I am leaning to the flame detection, since the response is to try to re-ignite. If everything starts at once, then I would be more in doubt.

You could block the air intentionally and see if that changes the action.

 

[Mouse]

OK -- i'll go try that. But, I don't know what part the flame detection would be in/around? I don't have the manual and can't find one online, but it does have a schematic:

 

[Mouse]

Does the blower start before ignition is attempted? If so, I am leaning to the flame detection, since the response is to try to re-ignite. If everything starts at once, then I would be more in doubt.

You could block the air intentionally and see if that changes the action.

You are definitely right that it's not the Blower Vacuum Switch that I originally thought. I turn it all on, everything is working, i pull the rubber tube and everything turns off. I put the rubber tube back and everything kicks back on.

Now I am leaning towards a bad thermostat since it doesn't look like it has any other heat detection unit? Part number 2 in the right diagram.

That or the Ignition Control (part number 5)

 

[Reach4]

It looks to me that the thermostat controls the blower motor. Then the blower vacuum switch, the thing in your photo, would close and tell the ignition control module to turn on the gas valve and the ignitor.

I agree that there does not seem to be a flame-detection sensor. Is it possible that they monitor the resistance of the HSI to determine if the flame is continuing? I don't know. The ignition control module is at the middle of things. I would look for a part number on that, and try that part number in a search engine.

You could try measuring the voltage from terminal TH to ground. I the blower is running, I think you should have a steady 24 VAC.

Bad thermostat means the blower will not run.

 

[hj]

Those numbers in the boxes are NOT "part numbers" they are the sequence that occurs when ignition is activated.

 

[Mouse]

Those numbers in the boxes are NOT "part numbers" they are the sequence that occurs when ignition is activated.

Well, I was using them as reference numbers so Reach4 could find them quicker. I wasn't going on google searching "water heater part #3"

 

[Mouse]

Bad thermostat means the blower will not run.

Yeah -- I don't think it's that either after reading up on it.

I drained out all the water from the unit, refilled it and everything is working fine now. So, I don't want to mess with it if it's working (kids and wife have to take showers tonight). What I may try doing is replacing the Ignition Control. It seems those have a tendency to fail, and when they do, the units act similar to what I am experiencing. I found one on Amazon for about 75$ (link).

I will keep you posted...

 

[DonL]

Yeah -- I don't think it's that either after reading up on it.

I drained out all the water from the unit, refilled it and everything is working fine now. So, I don't want to mess with it if it's working (kids and wife have to take showers tonight). What I may try doing is replacing the Ignition Control. It seems those have a tendency to fail, and when they do, the units act similar to what I am experiencing. I found one on Amazon for about 75$ (link).

I will keep you posted...

You may have a crack in the Hot Surface Ignitor.

A system like that measures its resistance to detect what it is doing.

If it opens for a split second it will shut the gas valve off.

I would check the Hot Surface Ignitor before replacing the Ignition Control.

Draining the heater or jarring it can make a bad / cracked ignitor open and close. Do not touch it with your fingers.

Good Luck.