HEATILATOR won't stay lit

[wizardofaz]

The HEATILATOR model GNDC36E is probably about 21 years old. We've been in the house for about 7 years and it has worked great every winter - until this one. I turn it on, it sparks, lights, the sparker keeps going, then the controller shuts off everything. The whole sequence is about 4-5 seconds. Doesn't vary at all. Lights perfectly, keeps sparking, then shuts off. There was no period of declining functionality. It worked perfectly up until the day it didn't.

On the controller (Robertshaw DS 845 NL-1-4) the red LED comes on blinking after it shuts off. The note on the manufacturer's label says
"If the red light stays on continuously, replace the control. For flashing light, refer to service instructions."
But of course I can't find any service instructions. I hesitate to replace the control, since if the blinking LED is working properly, it's saying the controller is not bad.

My intuition is the controller is not detecting the flame, even though the flame seems the same as it has always been. It's not obvious to me where the flame sensor is ... but I'm guessing it's one leg of the sparker.

Some pix are attached. Anyone who has experience or even a good idea, I'd appreciate it.

 

[Lennox65]

The HEATILATOR model GNDC36E is probably about 21 years old. We've been in the house for about 7 years and it has worked great every winter - until this one. I turn it on, it sparks, lights, the sparker keeps going, then the controller shuts off everything. The whole sequence is about 4-5 seconds. Doesn't vary at all. Lights perfectly, keeps sparking, then shuts off. There was no period of declining functionality. It worked perfectly up until the day it didn't.

On the controller (Robertshaw DS 845 NL-1-4) the red LED comes on blinking after it shuts off. The note on the manufacturer's label says
"If the red light stays on continuously, replace the control. For flashing light, refer to service instructions."
But of course I can't find any service instructions. I hesitate to replace the control, since if the blinking LED is working properly, it's saying the controller is not bad.

My intuition is the controller is not detecting the flame, even though the flame seems the same as it has always been. It's not obvious to me where the flame sensor is ... but I'm guessing it's one leg of the sparker.

Some pix are attached. Anyone who has experience or even a good idea, I'd appreciate it.

View attachment 309023View attachment 309024View attachment 309025View attachment 309026

I am not familiar with that system but generally, if the ignitor continues to spark after the pilot is lit, it means that flame rectification has not happened. The flame sensor could be faulty or the ground could be open.

 

[wizardofaz]

I am not familiar with that system but generally, if the ignitor continues to spark after the pilot is lit, it means that flame rectification has not happened. The flame sensor could be faulty or the ground could be open.

Lennox65 thanks for the reply. That was my general idea, that the flame was not being sensed and so the sparking continued, and eventually the controller shut it down. But two reactions to your comment:
(1) I don't see any pilot. Is there always a pilot? Visually, this looks like the sparker is right in the area where the main fire ends up appearing, and it just lights the fire from scratch.
(2) I wonder where the flame sensor is. I don't see any wired device in the vicinity of the flame except the sparker (ignitor) itself. Could the flame sensor be part of the ignitor? There are a couple pix in my post that show what the ignitor looks like.

Thanks for any more ideas anyone has. Obviously I'm just trying to avoid the $x00 repair bill if it can be a DYI.

BB

 

[wizardofaz]

OK answered one of my questions.

The ignitor and thermocouple are in fact the same device in this unit. And the thermocouple works. I put a multimeter on it and heated it with a gas match, got 30-45 mV out. I think this is as expected. And if I wanted to replace it, it's widely available. Cheapest source seemed to be Amazon.... go figure.

So now I think the best bet is the controller. If the controller is turning the gas on, the fire lights, the sensor is good, but the controller turns it back off, what else could it be? The controller is available, I may order one. If anyone has a great idea before that, please shout it out.

I've read elsewhere that the airflow may be the problem, but I don't think so in this case. But in case the issue was that I had the glass off so airflow was very different than normal, I tested again with the glass back on. Same result. Videos are attached.

The other thing I notice is that the the burner doesn't light everywhere. For some reason the flame doesn't light in the front right part of the burner. I suspect if the gas stayed on longer it would eventually light, but it is one thing that concerns me just a little. If I light that area with a gas match it lights fine. But then the controller still shuts it down in a few seconds.

Any more ideas from anyone, I'm listening. Thanks.

 

[Lennox65]

Direct Spark Ignition is the one technology that I have not worked with in my 27 years in the fireplace business, so I have absolutely no practical experience to share with you.

For whatever reason, you are not getting rectification. I don't know if it is in the rod, the wiring, or the module. It still could be the ground, have you found where that wire connects to the fireplace and checked it?

 

[wizardofaz]

Direct Spark Ignition is the one technology that I have not worked with in my 27 years in the fireplace business, so I have absolutely no practical experience to share with you.

For whatever reason, you are not getting rectification. I don't know if it is in the rod, the wiring, or the module. It still could be the ground, have you found where that wire connects to the fireplace and checked it?

Other people have suggested this problem is usually the ground. I did cut off the ring lug, cut the wire back a couple inches, and crimped a new lug on. I cleaned up the metal around the mount screw they used as a ground terminal. All to no avail. Also, I tested the thermocouple with it's ground by clipping a DVM probe to the chassis and the other probe to the sensor wire (unplugged from the control unit) and putting a small gas flame on the thermocouple. It generated 30-45 mV, which includes the ground in that test loop. So I think the thermocouple and its ground are OK.

I've ordered a new controller. Didn't want to do that while I had other ideas what it could be, but I've run out of other ideas. $200. Hopefully that will fix it. I'll post the outcome here, next week.

Thanks again for your help.

 

[Tjune54]

Usually the spark electrode becomes the rectifier, I would also replace the electrode assembly with the controller.

 

[wizardofaz]

Usually the spark electrode becomes the rectifier, I would also replace the electrode assembly with the controller.

Yes that's the case. I was able to get it to produce 30-40 mV with a gas match as a test.

The electrode assembly is another couple hundred bucks. I think I'll run with the old one until it fails. It's not that hard to get out.

Thanks for the reply and suggestion.

 

[wizardofaz]

Replaced the DS845 and that got it working again. Purchased from supplyhouse.com, that was the best price I found. Free shipping, 90 day return, no restock fee. And it got here in two days. Hard to beat.

 

[wizardofaz]

Here’s the old controller with the cover off. No smoked parts or otherwise obvious problem. Probably fixable with schematics and test procedure. I wonder if anybody wants it.