We have a 2004 Holiday Rambler (Monaco) Neptune and have had two serious problems we can't seem to resolve. First for two days up in Jackson, WY we smelled the same type of exhaust odor perceived from the outside vent, but the CM alarm did not go off (it was OUTDATED, my error). I had headaches for three weeks after returning. The technician found/repaired two propane leaks, replaced the furnace motor (the exhaust side of the motor was not working correctly), and replaced all carbon monoxide, propane and smoke alarms. Then last week, down in Moab, UT, the CM alarm went off the first night using the furnace, fire department responded, turned off furnace and propane, drama but no fire or explosion, etc. Our technician is working on issue today but after soaping all connections, hoses, etc. cannot determine problem. Any experiences or advice?Harold from Salt Lake City

On a home furnace, I'd suspect a cracked heat exchanger. Not totally sure the same logic applies to an RV, but I suspect it does.Jim, "Why do I wear loud socks? To keep my feet awake!"

I wonder how hard it would be to pull the furnace and have it tested on a bench. That would factor out a lot of issues. Some RVs, one can just lift up a dinette seat and have full access to the furnace. Others take some work to get at them.Barring a window or other hole open that would suck in air from near the furnace exhaust port on the outside, it either is a leak in the intake/exhaust line, or a cracked heat exchanger.

Could be cracked heat exchanger, blockage in exhaust, or a problem with fan motor housing. My other question is that most RV furnaces use only one motor to run blower and air exhaust for the combustion chamber. If the motor was bad both sides would have been effective.

CO is differant from Propane and I doubt that the propane detector can detect CO Rather than shutting down the furnace and gas they ( the firemen) should have used their CO detector to pin point the problem. I would bet that you have a broken heat exchanger in the furnace. AND any Rv furnace I have seen uses one motor and has a double ended shaft to power the blades. One for the heat and the other for exhust. Did he really put in a new motor? I would look hard at the heat exchanger. Don't forget CO is orderless so you can't smell it. And CO is lighter than air so you want a detector near the ceiling. Propane at the floor

Well, now, there ARE combination gas/CO detectors for both propane/natural gas and carbon monoxide. I have just such a unit in my workshop; bought it at Lowes.I don't know that they use them on RVs, but the technology is definitely in existence.I'm sure the OP knows about the toxicity and lack of smell of CO, having suffered a three week head ache. I trust he's also aware of how lucky he is to still be on this side of the grass.

Carbon Monoxide from Furnace | Good Sam Community

RoyB
Explorer II
Apr 25, 2014
After reading all of this I am thinking your furnace EXHAUST may have been blowing back into the trailer. That has to be very rich with deadly fumes - maybe not... I know the hot air feeding the heat ducks is sampled off this same hot air source so I guess I may not be that much aware how the furnace works. There certainly is alot of HOT AIR going to waste out of the outside furnace vent for some reason... One of my trailers comes out under the awning where we set alot and the other trailer vents out the back side of the trailer???

We don't use the furnace very much in the POPUP as it puts out way too much heat - runs us out there hehe..

Roy Ken
wa8yxm
Explorer III
Apr 25, 2014
One thing about heat exchangers.. We never had an alarm, not CO, not Gas, but the original furnace in my house, I decided to replace it with a new, more efficient one, with central air conditioning as well.

Well when they pulled the old one out I got a look at the heat exchanger.. There were several spots that were "Sealed" by flakes of rust, which of course broke loose hauling it up the stairs.. Thing looked like a colander.

I think I replaced it..... Just in time.

New one was much nicer, DSI, High effiency, Better air filter, Nice.
Ron3rd
Explorer III
Apr 25, 2014
dougrainer wrote:
On a 10 year old furnace, I would not pay the labor to replace the Heat Exchanger. Replace the Furnace and keep the module board and Fan Motor/Impellors for extra parts. MUCH safer this way. Doug

To the OP; I would listen to this man. Very experienced tech. Chris Bryant's another one, if he happens to chime in. Both these men know what they're talking about.
dougrainer
Nomad
Apr 25, 2014
TenOC wrote:
naturist wrote:
Well, now, there ARE combination gas/CO detectors for both propane/natural gas and carbon monoxide. I have just such a unit in my workshop; bought it at Lowes.

Propane is heaver than air and settles to the floor. CO is lighter than air and rises.

My Propane detector is near the floor. The CO detector is about halfway between the floor and the ceiling.

True, but a LOT of OEM's are using the combo LP/CO detectors now and they ARE mounted at the floor level. Doug
TenOC
Nomad
Apr 25, 2014
naturist wrote:
Well, now, there ARE combination gas/CO detectors for both propane/natural gas and carbon monoxide. I have just such a unit in my workshop; bought it at Lowes.

Propane is heaver than air and settles to the floor. CO is lighter than air and rises.

My Propane detector is near the floor. The CO detector is about halfway between the floor and the ceiling.
doughere
Explorer
Apr 25, 2014
I don't know as I'd trust a technician who replaced the motor because "the exhaust side of the motor was not working". Its a double shafted motor, both sides either work or don't.

Doug
dougrainer
Nomad
Apr 25, 2014
On a 10 year old furnace, I would not pay the labor to replace the Heat Exchanger. Replace the Furnace and keep the module board and Fan Motor/Impellors for extra parts. MUCH safer this way. Doug
beemerphile1
Explorer
Apr 25, 2014
loggenrock wrote:
Actually, in regards to carbon monoxide, it is considered "neutral" in regards to "density" as compared to air. The specific gravity of air is 1.0, this is what other gases are compared to. Carbon monoxide is 0.97 - for all practical purposes the same as air - meaning it neither rises nor sinks, but rather just blends with it, so unlike propane, which has a specific gravity of just over 1.5, this will settle to low spots. Conversely, natural gas is lighter, about 0.6, so it does rise. Therefore carbon monoxide detectors can really be located anywhere - high or low - and they will be effective. And I, too, like the ones with a digital readout AND a free-standing battery power source. ST

You are absolutely correct but for one thing. CO is most often caused by heat producing appliances. Heat rises.
loggenrock
Explorer
Apr 25, 2014
Actually, in regards to carbon monoxide, it is considered "neutral" in regards to "density" as compared to air. The specific gravity of air is 1.0, this is what other gases are compared to. Carbon monoxide is 0.97 - for all practical purposes the same as air - meaning it neither rises nor sinks, but rather just blends with it, so unlike propane, which has a specific gravity of just over 1.5, this will settle to low spots. Conversely, natural gas is lighter, about 0.6, so it does rise. Therefore carbon monoxide detectors can really be located anywhere - high or low - and they will be effective. And I, too, like the ones with a digital readout AND a free-standing battery power source. ST
wa8yxm
Explorer III
Apr 24, 2014
Regarding combo detectors.. Natural gas, like CO, is lighter (Well Less Dene for the nit pickers) than air so it rises toward the ceiling,

Propane, on the other hand, is heavier (More dense) so it tends to hug the floor.

This is why your explosive gas detector is mounted near the floor and your CO and SMOKE detector near (or on) the ceiling.

So yes, they do make combo explosive gas/CO detectors and yes they WILL detect Propane as well as natural gas, and Alcohol vapor, And gasoline vapor, and hair spray vapor and methane and a host of other gasses that have the ability to completely ruin your day if ignited.

But if mounted for PROPANE detection (near the floor) they are in the wrong place for CO and if mounted for CO detection (Ceiling or near it) wrong place for Propane. Thus you need two.

In a house however, You can use the combo near or on the ceiling since NATURAL gas is less dense and will rise to the top of the room.