Furnace Problem?

[2 DA WDS]

When I turn my furnace on it runs for a few minutes and then shuts down for a few minutes and then runs then shuts down and keeps doing this until it reaches the temperature set on the thermostat. Any thoughts?

Also, I was trying to adjust the fan speed on the fantastic fan and got it to run at full speed but when I push the arrow to turn it down nothing happens.

[BobW]

Make sure the battery is fully charged. Low voltage will keep the furnace from turning on.

[rverdlm]

There are several safety sensors in the furnace that along with low voltage could be causing the furnace to shut down. It's almost impossible to self diagnos this problem. One other problem I've had is low gas pressure. The way to check this is to light a burner and watch how it burns as the furnace goes on and off.

[BobW]

Once I had no heat from the furnace. After doing allot of checking, I found out that the hose in the tank compartment was kinked to the point that everything was not working. Check that area. It's easy to kink the hose while you slide the tanks back inside.

[2 DA WDS]

OK, the furnace actually lights and produces heat when it starts but it shuts down before it reaches the temp set by the thermostat. Then, it stays off for 2 or 3 minutes then starts, lights, produces heat and shuts off again. It keeps doing this until it does reach the temp set on the thermostat. Last fall I took it to a dealer because it would never stay lit and they said it worked fine for them. I told them to check the propane regulator and they said that it was bad and replaced it. Now I am having this problem.

[rverdlm]

I understood that from your first post. I still think all the things that have been suggested are good to check. Put a good digital volt meter at the 12V panel and see if the voltage changes as the furnace runs. If your charger is weak this would show it. The furnace draws a lot of 12V current and the battery could be drawn down, recharge, draw down etc. Same with the gas if the regulator is marginal. When it shuts down does the fan continue to run? It should run after the burner shuts off to remove the heat from the plenum. If the fan continues to run (that would probably eliminate the battery voltage as an issue) and it's only the burner that is cycling, that could be normal or it could mean that the burner is getting to hot and the over temp sensor is shutting it off. Have you checked in the 2 holes outside to be sure there is no dirt etc in them that could be causing a slight restiction in the air flow?

[2 DA WDS]

Yes the fan runs after the gas shuts off. The regulator has been replaces but could be a defective new one. Yes I have checked the input, that was one of my first thoughts that something was blocking that. I have tested the charger and its working properly. Someone suggested the limit switch.

[Huck]

I had a similar problem with my furnace when it was new.
It would start then shut down. I checked it all out and could not find the problem.
I got frustrated and switched the thermastat on and off a bunch of times fast, and it fixed it.
It has worked fine ever since.
Must have been a bad thermastat switch..

[berghild]

my furnace is basically worthless. it runs like crazy but not very much heat. howard found a that ductwork was not connected to the other ductwork....but fixing that didn't help. am ready to turn the furnace compartment into storage and buy a mr big neat and have it plumbed in like my neighbors did. mostly we just use electirc heater or the heat pumps. that won't help without hookups though in the desert this winter. grrrr

[hitchup]

The furnace on our 2006 Elite had problems during our 2nd winter in it. It would run, then shut off. It never would give out heat. RV Tech found loose wires. He tightened the wire nuts. Then it ran fine for a couple of months before it went out. So had it checked out at the dealer and it was more loose wires. Worked fine for the last cold winter in VA we owned it.

But I really like having two smaller furnaces in our 2009. They are keeping our larger unit more comfortable. We still supplement with one oil heater and most winter days, I only needed a long sleeved shirt to stay warm. It may help having the enhanced insulation.

[bstark]

This may sound a little technical but, Dave (rverdlm) has offered the best hope of a solution and here is how I would go about checking that overtemp out. You can isolate the point on the board that the feed from the overtemp pot comes back to the board and meter it while the furnace is running and observe if there is an interruption in current that is triggering the shutdown, if that isn't the problem go to another point such as the flame sensor to see if it is marginal and telling the furnace to shut down. You should do this with all of the furnace 'fail-safes' such as the sail switch, timer relay etc.. If you are not the least bit technically inclined, a good service guy or a friend that is handy could do this for you and it can be done during the summer when you're not as desperate for heat and can take the time to troubleshoot it correctly. Your dealers to date have simply done the basic "get-it-running,-bill-them-and-get-them-out-of-here" thingy!

berghild: These furnaces are rated at 42,000BTU's (due to the tapered duct attachment plenum on the back end) and actually do put out enough heat that you should be more than toasty in cold weather without the thing running non-stop. If there isn't enough heat coming out of the ducts I would surmise you've got a duct disconnect somewhere that is allowing all of the heat to go into the basement to be lost in the process. This can actually be worse than you imagine because the rear of the furnace is near the wall cavity (under it) that the thermostat is attched to and the heat 'escaping' from the rear of the furnace simply goes up that wall cavity and signals the rear of the thermostat that "all is warm now" so shut down.

[BobW]

This is what I did. Take the heater out of the RV. Hook it up to 12 volts. Connect, or short out the thermostat. Connect the gas line to a propane container. Basically what your doing is isolating the heater from the RV. If it works, the problem is in the RV. If not, go out and buy another furnace.

[berghild]

now those are some helpful ideas! I think the heat is escaping somewhere other than the one disconnected duct that Howard found.....but that's just a hunch. it doesn't shut down it just barely puts air out at the back of the coach and it's just barely warm (after it it warms up the ductwork I think). I have owned several other rigs and I know it should be keeping us plenty warm.
It has been 39 here in the sierras in the mornings and our lil' electic BIG HEAT is doing the job just fine for now. thanks for the help. Cyndy

[billr]

Our furnace was starting and going off, and would try to re-fire several times and not stay on. Ended up being a bad LP regulator on the tanks. Low pressure was being sensed and shut it down.

Bill

[Motor31]

Regarding the Fantastic Fan speed. Set it on manual then adjust the speed setting using the speed control. They aren't all that intuitive to operate.

[Diesel-Gypsy]

I have to confess, my furnace behaves in the same way......it lights, runs, then shuts off, waits a minute, then re-lights and continues to repeat that cycle until the coach is warmed-up.

Once the coach interior is at the desired temp it maintains the temp in short cycles of about 1 to 2 minutes every 5 or 6 minutes.
It depends a little on how cold it is outside.

I had it looked at in depth by a tech rep from Suburban at the Perry Rally last winter.
He took it out, changed parts, even changed the thermostat on the wall...
The results were marginally better.
He said it basically was a problem that he has seen many times, and it caused by DRV's installation.
It seems it is a combination of restrictive ducting, and poor return air.

The end result is we live with it..... :?

[2 DA WDS]

Diesel-Gypsy:
Interesting, have to ask about that at the rally.

Got my new Fantastic Vent control panel, works like its supposed to.

[rverdlm]

As I said before, if that is what is going on i.e. fan keeps running, but the burner goes on & off, that is how every RV furnace I've had works. There is a sensor that monitors the plenum temp and turns the burner off as required. The coach will come to temp as desired.

[Diesel-Gypsy]

Dave, I have had several other trailers with similar furnaces, the furnace in my Mobilesuite does operate differently.

It is basically a situation where the over-temp fail safe sensors shut the furnace off before it gets too hot because it cannot push the heat through the system quickly enough.

DRV now uses ducting with very low restriction higher volume ducting.
The furnace on these newer installations seems to work much better.

The fan on my furnace is doing exactly what it was designed to do.

Rick