Furnace Problems

[ParTheCourse]

Our Suburban SF35 furnace is acting up.

When the outside temperatures are in the mid 40’s or colder it has all it can do, with constant running, to get up to and maintain 65 inside.

I have removed the exterior cover and checked the intake and exhaust tubes and everything else visible to a layman and all is clear.

The blower seems to be working fine, hot air coming from the exhaust tube and warm from the floor registers inside, although at greatly differing temperatures not related to distance form the furnace.

The unit seems to ignite quickly, heat coming from the exhaust in the 15/20 seconds it takes to turn on the thermostat and get out the door and around the rig to it.

Then there seems to be a secondary ignition every few minutes lasting for 3/4 to 10/15 seconds. You can hear the ignition and then the blowtorch (raggity, spuddery) type sound. There does not seem to be any change of temperature from the exhaust during this time. I say “secondary ignition” because there is always heat coming from the exhaust however, you cannot hear the blowtorch type sound except during these short intermittent burns.

A mobile repairman charged $20 to remove the cover and verify that all was clear and hunch his shoulders.

Any thoughts on what's going on before we break winter camp and tow it to a dealer where they can get out and on the bench will be appreciated.

[ParTheCourse]

Our Suburban SF35 furnace is acting up.

When the outside temperatures are in the mid 40’s or colder it has all it can do, with constant running, to get up to and maintain 65 inside.

I have removed the exterior cover and checked the intake and exhaust tubes and everything else visible to a layman and all is clear.

The blower seems to be working fine, hot air coming from the exhaust tube and warm from the floor registers inside, although at greatly differing temperatures not related to distance form the furnace.

The unit seems to ignite quickly, heat coming from the exhaust in the 15/20 seconds it takes to turn on the thermostat and get out the door and around the rig to it.

Then there seems to be a secondary ignition every few minutes lasting for 3/4 to 10/15 seconds. You can hear the ignition and then the blowtorch (raggity, spuddery) type sound. There does not seem to be any change of temperature from the exhaust during this time. I say “secondary ignition” because there is always heat coming from the exhaust however, you cannot hear the blowtorch type sound except during these short intermittent burns.

A mobile repairman charged $20 to remove the cover and verify that all was clear and hunch his shoulders.

Any thoughts on what's going on before we break winter camp and tow it to a dealer where they can get out and on the bench will be appreciated.

[Ray,IN]

Your '08 5er is under warranty, before anything else I'l contact my dealer for service. You don't want to do anything that could be a loophole to void the furnace warranty. It should not be dirty enough yet to require cleaning. There are several things that can be the problem, testing by a certified technician is the best option.
Afterthought: The dealer may have a mobile service so you will not need to break camp.

[ParTheCourse]

Thanks Ray,

It’s 250 miles, 500 round trip to the nearest Newmar dealer in Fort Myers. The nearest large dealer with a substantial repair staff, for whatever good that is, with a good reputation around the CG is 5 miles away. They do not have road service.
It will be repaired under the Suburban warranty if there is any thing that needs repair, if it’s cleaning the orifice or something similar it’ll be on me.

[Tom N]

This may not correct your problem but it's an easy, quick check.

Pull the thermostat, unplug and reconnect all the wires.

-Tom

[ParTheCourse]

Thanks Tom, you got mail. Mike

[GaryKD]

The problem I've had with my furnace is the same as you describe. The furnace continued to reignite. Combine this with the built in wait time for the reigniting and the coach would not get warm. The solution for me was to replace the regulator. It seems I got some contaminated propane and the regulator had partially filled with the contamination. My only additional sympton was the regulator "gurgled" when the furnace was drawing propane from the tank. The furnace was the only appliance that had difficulty. I removed the regulator and a yellow colored liquid poured out.

[ParTheCourse]

Gary, Thank you for getting my head away from the furnace.

I will look at the regulator but as I do:

When we purchased this unit I had the standard size tanks replaced with 40#’ers. That placed the regulator 4/5 inches below the tops of the tanks. Seems I read a long time ago that the location is important and if I recall they are to be above or even with the tank tops and the valves.

“There are several things I can’t remember anymore.”

Googled the subject for an hour and can not confirm it, perhaps someone has knowledge of the requirements.

Thanks again,

[ParTheCourse]

While following GaryKD’s suggestion I found a kink in the hose leading from the regulator. It was under the trailer below gas compartment where the hose turns towards the rear.

Disconnected it from the manifold, pinched it back into round with pliers, rerouted it to prevent recurrence and presto, heat.

The cold front passage overnight provided the first opportunity for a test. 45 outside, 55 in up to 72 in about 50 minutes. What’s to old saying, “Now we’re cooking with gas”.

[GaryKD]

Mike,
My apology for not continuing the thread. Somehow I did not see your post, after my post. I'm glad to see you discovered the problem. I do not think the position of the regulator in relatioship to the propane tank is important. On motorized Newmar coaches the regulator is positioned around the middle of the tank. The regulator does need to be installed with the vent hole pointing down. This hole has a mesh screen over it. This ensures moisture will drain from the regulator and not be trapped, in the regulator and freeze up the regulator.