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Furnace Heater Trouble Shooting- Help Needed


Jules the Dolphin

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Hi All,

 

Recently purchased a 1986 Dolphin with 38k. Most everything works but the furnace is not emitting heat. Propane is hooked up and works to light the hot water heater and stove and the furnace comes on but only blows cold air. I thought maybe it just needed to be left on for a while to cycle through the air and allow the propane to flow but its been going for about 30minutes and still only has cold air coming out. Any advice for trouble shooting this?

Thanks!

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Heaters are simple IF you understand "things". Are you running the heater off the house battery or is your rig plugged into a 115v source?

Failure points, heater blower, sail switch, ignitor points, control board, gas valve.

Check outside vents for critter nests. Cycle it 6 times while plugged into 115v. IF your battery is a bit low the blower won't spin fast enough to trip the sail switch.  Without the sail switch tripping there is no heat.

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On 10/26/2016 at 5:00 PM, WME said:

Heaters are simple IF you understand "things". Are you running the heater off the house battery or is your rig plugged into a 115v source?

Failure points, heater blower, sail switch, ignitor points, control board, gas valve.

Check outside vents for critter nests. Cycle it 6 times while plugged into 115v. IF your battery is a bit low the blower won't spin fast enough to trip the sail switch.  Without the sail switch tripping there is no heat.

WME has the right advice. When you turn on the thermostat you should hear the fan start. When the fan has been going a short time it causes enough air to push the sail switch (looks like a boat sail on a hinge) to "on". When the sail switch goes on (makes continuity) it signals the control board to open the gas valve (clicking sound) and fire the ignitor points (sparking sound), you should hear the click of the valve opening, then the sparking of the ignitor points, then the sound of a rapid flame (Whooshing sound like a flame thrower). My heater had 4 problems when I first got it. (1) Poor motor bearings caused slow fan, so I lubed the bearings and still have to relube once in a while. (2) the sail flag was misaligned and sticky, I cleaned lubed and re-positioned it and tested continuity when in the on position, it was OK. Still no fire, so (3) I got a new control board, about $100, from Dinosaur? in Portland Oregon. Now I had the  click of the gas valve and a sparking sound but still no fire. (4) I looked at the sparking points and they were not sparking where the gas flow was happening, they had been pushed against the frame, so they would spark but not light the gas so the control panel would shut off the gas. When I got the spark where it needed to be I finally had heat. You must also have propane gas at the right pressure at the heater valve for operation, I did not have that problem, hey 4 out of 5 ain't bad, and I did not have the bug nest in the air intake or exhaust problem either. Your thermostat is probably fine as it started the blower. Good Luck

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  • 2 years later...

Experiencing similar issues.  Symptoms so far are as follows: blows cold air fairly well (the sail likely works) .  I hear the tick tick tick tick of (presumably) the igniter trying to fire the propane that i do smell when troubleshooting (so valve is opening).

A couple or three days before heater went out, I noticed what sounded like the aforementioned tick tick tick tick tick that seem to continue even after fire was lit.   This is probably relevant to the trouble shooting process. 

Any ideas?  Temps are dropping a bit in this solstice night.  

 

Many thanks.

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Thermostat turned on, fan runs on prepurge, sail switch and over temp proof,  gas valve opens, ign begins,  if the flame is not sensed the gas valve closes and the ign stops. In the case of the older igniter boards the furnace will run till the battery is dead if it does not light. The most common problem is the board as long as you have good airflow. A modern board is a good upgrade even if it's not your problem they try at least 3 times to light (old boards quit after one try) and are smart enough to turn the whole affair off if it does not light. Dinosaur boards are first class worth the money. There are other problem with old furnaces such as being completely rusted/burned out but most of the ones I have fixed it's generally been the board or a motor not turning or turning slow. Some rv shops have testers but they tend to pass boards that do not provide enough spark.

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A quick check to eliminate a few things.. Try running the truck engine when you turn the heater on.

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13 hours ago, Mister Blu said:
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Experiencing similar issues.  Symptoms so far are as follows: blows cold air fairly well (the sail likely works) .  I hear the tick tick tick tick of (presumably) the igniter trying to fire the propane that i do smell when troubleshooting (so valve is opening).

A couple or three days before heater went out, I noticed what sounded like the aforementioned tick tick tick tick tick that seem to continue even after fire was lit.   This is probably relevant to the trouble shooting process. 

Any ideas?  Temps are dropping a bit in this solstice night.  

 

Many thanks.

 

 

Not sure how the 'hidden comments' thing happened, but if it's something you managed to do, please don't. Many, myself included, don't like clicking on 'mysterious' links! :)

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Likewise.  Not sure how that happened.  Never saw it before.  Thought it weird.  Hopefully, that istaken care of.  

Let me know if it is not.  

 

...and pardon.  If it was, indeed, my doing.

 

 

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1 hour ago, WME said:

A quick check to eliminate a few things.. Try running the truck engine when you turn the heater on.

Tried with engine off and adequate batteries power.  

Tried with engine on and idling.  Tried with engine on and driving.

Tried while connected to shore power.

Although the fan occasionally squeeks a bit, it is not impeded by lint, dust, dirt, or other debris.  That i can see.

 

 

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One reference I found did mention one possible cause being bad high tension wire, or loose connection.  I hear it ticking(presumably igniter trying to light a fire).   

And as I mentioned before, a few days prior to furnace going on the fritz, i did noticed that I heard the same tick tick ticking even even after furnace flame was lit.   Related?  

How much is a compatible, upgrade board?

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2 minutes ago, Derek up North said:

All normal this time, so one of the Interweb's mysteries. You aren't Russian or Chinese by any chance? :)

 

No, not much of a Russian here.   

Personally, i enjoy going a bit slower.  Taking my time.  

Even when i am a running bee-hind.

and no.  Never been to China.  

Earthling maybe.  God's country.  Currently living in the P.N.W.  

Frost last night.  

Which is more cost/time effective... a Mister heater, or fixing this?

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19 minutes ago, Mister Blu said:

One reference I found did mention one possible cause being bad high tension wire, or loose connection.  I hear it ticking(presumably igniter trying to light a fire).   

And as I mentioned before, a few days prior to furnace going on the fritz, i did noticed that I heard the same tick tick ticking even even after furnace flame was lit.   Related?  

How much is a compatible, upgrade board?

Mine had the same symptoms, had to put it on the bench for testing in order to find out the spark gap was too wide. Electricity will find the shortest path to ground so if it is not sparking at the gap it could be sparking somewhere else outside the fire chamber. If the wire gets a crack in the insulation this could happen. The board senses flame with the spark wire. If the wire is broken somewhere or the coil is shorted on the board the electronics will not see flame and try to relight. Note the gasket died when I pulled the view port hatch off. It took a few tries to get the correct. The gasket is important to keep those bad gasses out of the heated air!

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My 1986 Sunrader the furnace didn't work when I got it. Squeaked like crazy and motor ran but no heat. Very low miles so the camper had spent lots of years just sitting and southern Cal so no heat needed. Motor was just running slower from disuse. I gave it some use. Turned it on and off dozens of times. On, all the way off at thermostat, wait 5 minutes, then on again. Gas appliances you have to wait a while like a home water heater. Finally got the furnace to light and it squeaked a lot but worked. After a while the noise quieted down too. 

Now 14 years later it's not running up to snuff again. Sprayed fan post with WD40 and got it working for a while but I should have used a dry lubricant like graphite type spray. Works when it's warm outside but not cold when I need it. Going to buy a new motor. There are ones I think will fit on ebay. Waiter or WME replaced their motor a few years ago and worked out well. Will clean and align sail switch while I'm in there. 

Linda S

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3 minutes ago, linda s said:

My 1986 Sunrader the furnace didn't work when I got it. Squeaked like crazy and motor ran but no heat. Very low miles so the camper had spent lots of years just sitting and southern Cal so no heat needed. Motor was just running slower from disuse. I gave it some use. Turned it on and off dozens of times. On, all the way off at thermostat, wait 5 minutes, then on again. Gas appliances you have to wait a while like a home water heater. Finally got the furnace to light and it squeaked a lot but worked. After a while the noise quieted down too. 

Now 14 years later it's not running up to snuff again. Sprayed fan post with WD40 and got it working for a while but I should have used a dry lubricant like graphite type spray. Works when it's warm outside but not cold when I need it. Going to buy a new motor. There are ones I think will fit on ebay. Waiter or WME replaced their motor a few years ago and worked out well. Will clean and align sail switch while I'm in there. 

Linda S

The motors use oilite bearings. They are factory impregnated with oil and the oil gets used up after some time. Friction heat pulls the oil out of the bearing towards the shaft that's why it gets quiet after a while. You can not replace that oil. Not sure that adding oil will work long term. Usually a motor replacement is in order.

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6 hours ago, Gulfstream Greg said:

Mine had the same symptoms, had to put it on the bench for testing in order to find out the spark gap was too wide. Electricity will find the shortest path to ground so if it is not sparking at the gap it could be sparking somewhere else outside the fire chamber. If the wire gets a crack in the insulation this could happen. The board senses flame with the spark wire. If the wire is broken somewhere or the coil is shorted on the board the electronics will not see flame and try to relight. Note the gasket died when I pulled the view port hatch off. It took a few tries to get the correct. The gasket is important to keep those bad gasses out of the heated air!

How to access the " spark gap". To check if it is functioning properly.   Is this what the "view port" is for?

 

 

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In my situation, any squeal is nominal, and seems to be more prevalent with a depleted battery.  Maybe a good cleaning.  

As far as the furnace not firing... well, it did tonight.  It isn't going right now.  Over the last two or so days, I have tried it in different situations trying t g it to light.  This evening, it fired up and i was not plugged in to shore power.  First time in two or three days.

not sure if it will fire up again after it turns off, we will see.

Any ideas?   

Ignitor positioing maybe?

Can some one offer a link to a replacement control module, preferably the upgraded one?

 

 

 

 

 

 

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If it’s the board, I have a new dinosaur UIB-L in my shop. If it fits your furnace it’s yours for postage. 

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The boards do that sometimes they work other times they do not usually when it 35* in the middle of the night and the fan is blowing cold air. Dinosaur has pictures of the boards on their site you can match it to yours.

 

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23 hours ago, Mister Blu said:

Got any links for motor?   

And for an upgrade board?  

Preferably Amazon for ease of purchase, and delivery.  

https://pdxrvwholesale.com/products/atwood-hydroflame-furnace-model-8516-ii-tune-up-kit

And the manual https://dunesport.com/manuals/atwood-furnace.pdf

I don't see a window in the manual for watching to see if you actually get spark. 

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There is a tiny dime size window that will allow you to see the flame but that's about it. Is  it warm? Yes then you have a flame. Is it blowing cold air? Yes then it didn't light! They are designed not to blow the side out of your camper and are over engineered to do so, so the fail safe devices work very well. The bottom line the buck stop at the control board so if it does not light something was/is amiss. My bet is on the board they get flaky with age. 

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Greg that PDX RV wholesale is a great resource. I used to rely on PPL RV parts in Teas to help people find the parts to fix stuff but they no longer have the superstore that used to have everything with diagrams. I saved that site. Man I wish I knew about that all along. Clearer and easier to negotiate than PPL was. Not to mention they have the blower motor I need. 

Linda S 

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I have a 1984 Toyota Huntsman. The furnace will only come on if I start the truck. It will blow warm air for a while, then the flame will go out and it will blow cold air.  What' up with that?

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Possibility... a dying fan motor. Its stiff and doesn't blow enough air to trip the safety fan sail switch. When you start the truck the motor gets extra voltage, like 12 vs 13.5 , after the heater starts you probably stop the truck. Then the voltage drops back to12 and the fan slows down and eventually the sail switch trips and the fire stops. OR the fan slows and the air flow is reduced and the heat chamber overheats and the safety temp sensor trips.

The fix is a new motor, maybe a clean and lube the motor and sail switch will get things going. But your motor is 35 years old and just may be worn out.

 

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On 12/29/2018 at 4:25 PM, WME said:

Possibility... a dying fan motor. Its stiff and doesn't blow enough air to trip the safety fan sail switch. When you start the truck the motor gets extra voltage, like 12 vs 13.5 , after the heater starts you probably stop the truck. Then the voltage drops back to12 and the fan slows down and eventually the sail switch trips and the fire stops. OR the fan slows and the air flow is reduced and the heat chamber overheats and the safety temp sensor trips.

The fix is a new motor, maybe a clean and lube the motor and sail switch will get things going. But your motor is 35 years old and just may be worn out.

 

Sometimes I've had good luck pulling fan motors and re oiling the felts that hold the oil that oils the bearings over time they dry out.

Another trick if everything checks out but the furnace won't fire is to lightly tap the body of the gas valve with say a screw driver handle. Gas valve guts can stick and not operate after sitting for a long time.once working cycle a few times to exercise the valve.

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