Heatilator Quit working!

[tablerock]

I have a Heatilator GNDC30, around 20 years old that started having issues this season. It started out not wanting to stay lit, would require relighting occasionally, or multiple attempts to light. Then, more recently just quit working altogether.

This model has a pilot light and it does stay on correctly. I have no experience with home HVAC repair, but was able to replace the igniter/thermocouple/thermopile assembly yesterday. Put it back together, got the pilot going, and nothing happens when I flip the switch on. No clicking/sparking at the ignitor. I put a voltmeter on the wires coming from the thermopile with the switch off and its around 760mv, but does not change when I flip the wall switch. I read on a troubleshooting chart somewhere that it should drop in half when switched.

With my meter on the 2 leads coming from the wall switch, I get the same 760mv when switched off, drops to 0 when flipped on.

I don't get any clicking noise when the wall switch is flipped on and I don't see any arcing either. I'm not sure if I should or not.

Any ideas? Things with me are always going to be something off the wall. Like a spider web in the gas tube or ???

 

[DAKSY]

Try jumping the TH & TH-TP terminals with a wire or paper clip. See if it starts. If it does, your wall switch might be the culprit.

 

[tablerock]

Thanks, I just did and nothing happens.

 

[DAKSY]

Try rapping on the side of the valve with a plastic screwdriver handle. A solenoid could be stuck. If that doesn’t work, the valve may be shot. 20 years is a long life for a gas valve.

 

[tablerock]

I actually did try this before replacing everything. Just went back and tried again and nothing. My guess is that it's the valve. I priced one on Fire-Parts.com that does not have the "turn down" feature. It's $85. To buy one OEM or with the turndown feature is upwards of $250 to $300. I don't see where my model has the limit switch anywhere, or any other switches otherwise.

Could I have possibly done anything wrong in my installation of the pilot assembly? Pilot looks normal, but could the bracket that holds it or the gas tube assembly need adjusted?

 

[DAKSY]

I don’t think so. The valve is a fairly simple mechanism. If the electromagnets are charged by the thermopile, they open to allow gas flow. You could try dropping the mV by turning the adjustment screw, down to about 550mV, but I think your valve is history.

 

[49er]

It's unlikely but I wonder if there's any chance you might have gotten a wire in the wrong place when you replaced the pilot assembly? It might be worth posting a picture of your valve if you can.
It sounds like you have a standing pilot so I wouldn't expect any clicking or sparking at the ignitor. You would only get a spark when you pushed on the manual ignitor button.

 

[tablerock]

I actually took a pic of the 2 wires coming from the thermopile before removing them from the gas valve, so I know they are correct. That leaves me with the 2 coming from the wall switch. i actually disconnected them again and reversed them just to try it the other way and made no difference. There is another pair of wires that lay in the floor pan that come out of the wall that were never hooked up. My guess is they are for an optional thermostat? Either way they were never connected.

Leading up to all this, my pilot lite had grown to a pretty big constant orange flame several inches high. After replacing the pilot assembly, I have a nice, squatty blue flame.

 

[DAKSY]

The thermopile wires should be connected to the TP & TH-TP terminals, & the screws should be snug

 

[49er]

You're most likely looking at a new valve as DAKSY has already mentioned.
As a homeowner like yourself though, there is one last thing I would check before ordering the valve. With your wall switch turned on, put your meter leads on the valve terminals TH and TP. Are you seeing 760mv across those terminals?

 

[tablerock]

You're most likely looking at a new valve as DAKSY has already mentioned.
As a homeowner like yourself though, there is one last thing I would check before ordering the valve. With your wall switch turned on, put your meter leads on the valve terminals TH and TP. Are you seeing 760mv across those terminals?

With wall switch off I’m getting like 788mv,
With wall switch on, 764mv.

 

[tablerock]

Here is a pic of the valve with wiring.

 

[tablerock]

Here is a pic of pilot quality. I never put the log assembly back in. Threw everything else back together to see if it was working after the pilot assembly replacement and it wasn’t.

 

[49er]

Everything looks good to me so I guess it's time to order a new valve.

When you got these readings, you had your meter connected to the top and middle terminals on the valve?

With wall switch off I’m getting like 788mv,
With wall switch on, 764mv.

 

[tablerock]

Everything looks good to me so I guess it's time to order a new valve.

When you got these readings, you had your meter connected to the top and middle terminals on the valve?

No, measurement taken between middle and bottom terminals.

 

[49er]

No, measurement taken between middle and bottom terminals.

That makes more sense.
The top and middle terminals are connected to the coil in the valve. You should see 0 volts between them with the wall switch off and 760mv or so with the switch on. As you know, that voltage will be pulled down to something less when you get your new valve in.

 

[fortune-cookie]

Make sure the wall switch is functioning correctly. If it's a simple on/off switch, you can try bypassing it temporarily to see if the fireplace turns on. You can do this by connecting the wires that go to the switch directly. If the fireplace turns on when bypassing the switch, it might be a faulty switch.

 

[tablerock]

Success! Replaced the gas valve and fired right up. Thanks for your help.