Suburban Furnace Lites, Then Goes Out

FireMech · 06-12-2015, 04:50 AM

The igniter is sparking, the blower is working, the burner lites then goes out right away and it does this 3 times before it goes into lockout. I tried blowing out the vents, cleaned and adjusted the igniter and I am sure I have correct battery voltage.

I found the propane regulator switch (I have 2 tanks) to be defective (low flow) when switching the selector to run on both tanks. Selecting one tank seems to have adequate flow when the stove is on. I hope to replace the regulator today except I am camping 1 hour from town and will need to find a RV parts store.

I'm thinking the flame sensor on the igniter is bad however I see a lot of people on the forum have had bad control boards. Any thoughts on what is defective?

cb1000rider · 06-12-2015, 07:29 AM

I've had this experience too (with Jayco, not that it's a Jayco furnace). In my case, it was solved by re-positioning the igniter, which is also the flame sensor. It sounds like you tried adjusting it.

scott24 · 06-12-2015, 05:08 PM

Make sure the furnace is grounded properly. Can also check the DC microamps on the flame sensor as well

therink · 06-12-2015, 05:44 PM

I would remove the flame sensor and sand it well using sand paper. If that doesn't work, run a small brush through the burner tube (or compressed air). All it takes is a spider Web to alter air flow to burner.

FireMech · 06-12-2015, 08:42 PM

I wasn't able to get a replacement igniter/flame sensor but I sanded the igniter again and re-positioned it closer to the burner. By doing so the solder joint broke loose. I don't have a solder gun with me but I was able to secure it tightly, temporarily. I re-installed and it fired right up!

Later I tried it again and I'm still having the same problem. I'm thinking my temp fix came loose. We are headed back home tomorrow so I'll order a new igniter and will let you know the outcome.

How do I check the micro amps on the flame sensor?

Is the burner tube the brass looking device with the very small single hole?

I'll check to make sure the furnace is grounded correctly.

PerryB · 06-12-2015, 08:55 PM

How do you set the selector to run on both tanks? I'm on my fourth trailer and have not seen this feature. I'm pretty sure its either right or left. I don't think centering the valve is a "both" position. -- Maybe I'm missing something? ....

FireMech · 06-13-2015, 05:05 AM

PerryB, you are correct, centering the selector is not a both position. Thanks for clarifying this.

It didn't get too cold last night without the furnace. I did turn it on this morning just to see if it would work and it fired right up. However, after about 15 minutes it shut off before it reached the set thermostat temp.

PerryB · 06-13-2015, 09:26 PM

I had an issue last fall where I noticed my furnace had a thready/ragged sound and not a solid rumble like it used to. Also reduced heat, although it never quit burning. I noticed I could hear the gas whistling through the regulator. I replaced the regulator and both pigtails and normal operation returned.

elranas · 01-16-2021, 06:20 AM

Quote:

Originally Posted by PerryB

I had an issue last fall where I noticed my furnace had a thready/ragged sound and not a solid rumble like it used to. Also reduced heat, although it never quit burning. I noticed I could hear the gas whistling through the regulator. I replaced the regulator and both pigtails and normal operation returned.

How did you reduce the heat?

**chuckster57** · 01-16-2021, 07:01 AM

Welcome to the forum

PerryB didn’t “reduce the heat”, the loss of heat was from poor gas flow. RV furnaces don’t come with any device to reduce heat output.

elranas · 01-16-2021, 07:08 AM

Quote:

Originally Posted by chuckster57

Welcome to the forum

PerryB didn’t “reduce the heat”, the loss of heat was from poor gas flow. RV furnaces don’t come with any device to reduce heat output.

That makes sense. *I was just curious because I think mine runs too hot.

**chuckster57** · 01-16-2021, 07:12 AM

Quote:

Originally Posted by elranas

That makes sense. *I was just curious because I think mine runs too hot.

There is an “over limit” switch that will shut the flame off if the furnace gets too hot. If yours is blowing good heat, I would say enjoy it, too many people complain of not enough!!

elranas · 01-16-2021, 07:22 AM

Quote:

Originally Posted by chuckster57

There is an “over limit” switch that will shut the flame off if the furnace gets too hot. If yours is blowing good heat, I would say enjoy it, too many people complain of not enough!!

It does blow enough air but my furnace flame goes off every 4 minutes and after a 1 minute of colling it comes back on. This cycle repeats until the thermostat temperature is met and then all the system with shut off. Most people tell me that a furnace shouldn't get so hot for the hi-limit switch to trip. It is a safety switch not part of the normal operation (on/off all the time) of the furnace. My sole concern is that due to something faulty my furnace gets too hot and I'm abusing the hi-limit switch and it won't work when I really need it.*

elranas · 01-16-2021, 07:29 AM

AirExcel sent us a new furnace and it does the same thing. We replaced the gas regulator, thermostat, added two more 4" ducts and even bench tested the unit and it still does the same thing.

**chuckster57** · 01-16-2021, 08:01 AM

Quote:

Originally Posted by elranas

AirExcel sent us a new furnace and it does the same thing. We replaced the gas regulator, thermostat, added two more 4" ducts and even bench tested the unit and it still does the same thing.

On the bench, no ducts hooked up and it will run, get hot, shut off the flame and then re light?

Have you used an ohm meter on the over limit switch during bench testing?

elranas · 01-16-2021, 11:04 AM

Quote:

Originally Posted by chuckster57

On the bench, no ducts hooked up and it will run, get hot, shut off the flame and then re light?

Have you used an ohm meter on the over limit switch during bench testing?

Yes, that's exactly what it does.
Yes, I tested the hi-limit switch while running and it opens when the furnace is too hot -- and it gets HOT.

**chuckster57** · 01-16-2021, 11:07 AM

Do you have a temp gun to see what temp it shuts off at?

Have you measured the gas pressure when running?

elranas · 01-16-2021, 11:27 AM

Quote:

Originally Posted by chuckster57

Do you have a temp gun to see what temp it shuts off at?

Have you measured the gas pressure when running?

I don't have a temp gun but I can get one from Home Depot. What would I be testing? The temp from the register?
No, I measured the pressure when the furnace was off. Did I do it wrong?

**chuckster57** · 01-16-2021, 12:05 PM

You want to measure the temp at the over limit switch with an ohm meter hooked up. I want to know at what temp the over limit loses continuity.

Gas pressure should be measured using a manometer at the gas valve of the furnace if you can access it while running.

**JRTJH** · 01-16-2021, 12:48 PM

There should be the same 11"/water column (about 0.5PSI) gas pressure in the entire LPG system. From a very simplified explanation, if the stovetop burners don't "spit flame away from the burner holes" and if the refrigerator works properly on gas, there's probably not an "excessive gas pressure" in the system.

That said, I wonder if the burner jet is possibly the wrong size ? If the hole is too big, it would allow excess LPG to enter the burner tube, making more heat then should be there. Sort of like turning a stovetop burner on high regulates more LPG to the burner and the flame gets larger and hotter.

Another possibility, if the burner tube is not aligned properly, it could aim the flame against the side of the tube (closer to the high temp switch) which "mechanically" causes the switch to get too hot....

What concerns me (and I have no answer for) is why two furnaces are doing the same thing ???

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