Furnace RPM's

[whutfles]

We have a 2010 Montana Mountaineer 326RLT. It is in storage plugged into 110V to keep batteries charged. I went out the other day to put new silicone caulking on the shower door. Temps were below freezing so I turned on the propane and turned the furnace on. Then I carried some tools into the RV and noticed hot air was comming from the furnace exhaust outside near the door so I knew the furnace was working. I had the ceiling lights on in the kitchen, LR and hallway. Then I noticed the furnace RPM's were slowing about every 10-15 seconds to about 3/4 speed for a couple of seconds and then return to full RPM's. When the furnace slowed, the lights were slightly dimming also. The longer I watched it, the slower the furnace slowed and the dimmer the lights dimmed. So I turned the lights off and the furnace continued to cycle fast to slow to fast. I was going to leave the furnace on overnight to allow the caulk to dry. But I was concerned I might damage the furnace motor if it continued to slow. The battery test in the panel said the batteries were fully charged. I checked the battery connections and there was no corrosion. I have 2 Interstate AGM 31M batteries. So after about 20 minutes of watching this, I turned the lights back on and the furnace started running normal and the lights quit dimming.

I read somewhere when I first bought these batteries that they can go to sleep and someone used a welder or something to put a heavy load on these AGM batteries to wake them up as they supposedly go to sleep. Is that what I have here? Did my batteries go to sleep? Or do I have some other problem?

We have not had the luxury of being able to plug into 110V in the past. Only recently moved to a different storage site. So in the past, charging the batteries was limited to plugging in the truck and running it for a while.

[AZ Traveler]

You didn't say if you have just plugged into 110 or it had been hooked up for awhile. If you had just plugged in, your batteries may have been way down on charge and your converter was overloaded trying to run lights, run the furnace blower and charge the batteries all at the same time.

Your battery indicator on the panel will always show a full charge when you are hooked to shore power and the batteries are being charged. The indicator is not very accurate but will only give a good reading after the batteries are disconnected from the charger for 30 minutes or so.

If your batteries were discharged it could take several hours plugged in to top them off.

[whutfles]

They've been plugged for about a month in this new site.

[DQDick]

Were your slides in when running the furnace? If so, how many of your vents were covered?

[whutfles]

Slides were in. The one in the kitchen and the one in the living room were each about 1/3rd covered.

Once it started working right, it ran OK for the next 3 hours while I was there and it was tosty warm the next day.

[drknapp]

I have noticed that when our water heater kicks on (when set to electric) and our furnace is running, the fan speed slows a tad and then kicks back up when the water heater kicks off. But it's not a large variation in speed.

[whutfles]

DRKNAPP - Well your water heater is 110V and your furnace is running off the 12V battery. So it's a combination of the load from the water heater and the converter that charges your batteries. What was your power source that the RV was plugged into - 50 Amp, 30 Amp or 15 Amp?

In my case the furnace and the lights were all 12V and I was plugged into 15 Amp. So it was just the load that the converter was drawing.

[rohrmann]

Just a suggestion that should be a maintenance item, is get into your breaker/fuse panel and tighten all the connections, both the 12 volt DC and the 120 volt AC at the breakers, and any other connections you can see there. Also, all the connections where the batteries are should be checked for loose connections too. The fluctuation in motor speed can be caused by loose connections. You may want to disconnect from the AC power coming into the trailer just to be safe, and just be careful when tightening the 12 volt DC connections. If you have a battery disconnect switch, you can turn that off so there is no voltage in the panel if you are more comfortable with that.

[whutfles]

ROHRMANN - Thank you. That's a very good suggestion. We have 2 DC lights that quit working last year - one over the dinette and one over the couch - all in the large driver's side slide. No bad fuses and connections all look good at the lights in the ceiling and no pinched wires visible under the slide. Just no power at the lights. i suspected a loose connection at the fuse box for that problem.

Does the fuse pannel pull out from it's front into the cabin or do I have to remove the rear wall in the garage to get to it? My panel is just to the right of the door as I enter the RV.

And by battery disconnect, you are not referring to the one in the convenience center, but a separate one at the battery, right?

[Carl n Susan]

Originally Posted by whutfles

<snip>...We have 2 DC lights that quit working last year - one over the dinette and one over the couch - all in the large driver's side slide. No bad fuses and connections all look good at the lights in the ceiling and no pinched wires visible under the slide. Just no power at the lights. i suspected a loose connection at the fuse box for that problem...
</snip>

This is a common problem. There is a junction box under the slide in the back corner. It frequently leaks and causes corrosion of the 120V and 12V wire connections inside. Remove the cover and check for 12V there.

[whutfles]

Just spent the afternoon at the RV with no heat, froze my fingers. I found the negative terminal on the 2nd battery was loose.

I removed the cover off the entrance panel and fortunately all terminals were accessable from inside the RV. All of the hot wires to the 12V fuses were tight. And all of the black wires to the 120V breakers were tight. 2 of the white ground wires were loose. And 3 of the uninsulated ground wires in the second row back had never been tightened - the wires were just lying behind the bolts. I'll try to put some pics on here of the pannel. The left pic is with the cover on with lid removed and the right pic is after cover is removed.

I took the wood grill off the front of the furnace trying to access the junction box with the electrical connections. Well, no junction box, just 3 wires sticking up beside the furnace with plastic crimped connections on them. There is a metal cover along the entire side of the furnace nearest the wood grill for access to the heat exchanger. It has 2 metal screws holding the cover on. One screw was laying on the floor. Replaced that screw, vacuumed around the furnace and reclaimed a couple of my wife's plastic spatulas that had fallen down beside the furnace from one of the drawers.

I reconnected the batteries, reconnected to power and turned on the furnace. It ran great. So thanks for the suggestion to check the terminals.

It still did not correct the 2 12V lights that don't work in the large slide. So I'll wait till we get in warmer weather next month and try to find the junction box CarlNSusan referred to.

[beeje]

My 2011 unit has no under slide junction boxes. I also found many loose wire connections in the panel.

[whutfles]

My large slide has a 6 or 8 inch high plastic apron with the electrical wires attached to it that supports the wires as the slide is taken out. The wire goes up into the slide near the outside edge and goes into the RV where the floor meets the wall. So I'm going to have to drop the underbelly cover and go fishing to find any junction box.

[beeje]

whutfles, my unit is just like you described. I have had almost all of the coroplast covering off my unit to repaint the frame and install new Valterra valves. There were no junction boxes anywhere in there. I can only assume that the wire runs and home runs straight to the electric panel.

[rohrmann]

On our rig, there are inside junction boxes in the slides, covered with carpet and attached with a few screws. I've never had a need to expose them, but we have no external boxes under the slides, so I'm guessing this is where the connections are located. The photo is of the box that is at the back end of the large curb side slide behind the sofa. Looks like a water stain on the wall, but that is just a shadow from the flashlight on the floor I had aimed at it. I have had our sofa slid out several times in the past due to water leaks, and it is not anchored down, just heavy to move, but doable.

[whutfles]

Thanks ROHRMANN. I'll check under my couch.

[kencare]

Originally Posted by whutfles

ROHRMANN - Thank you. That's a very good suggestion. We have 2 DC lights that quit working last year - one over the dinette and one over the couch - all in the large driver's side slide. No bad fuses and connections all look good at the lights in the ceiling and no pinched wires visible under the slide. Just no power at the lights. i suspected a loose connection at the fuse box for that problem.

Does the fuse pannel pull out from it's front into the cabin or do I have to remove the rear wall in the garage to get to it? My panel is just to the right of the door as I enter the RV.

And by battery disconnect, you are not referring to the one in the convenience center, but a separate one at the battery, right?

Had light over the desk slide quit this summer, switched out light unit with one that was working nothing. Got into wire loom under rear of slide, found wire broken and corroded, cut off corrosion, new connector and heat shrink back into loom. Everything is good.

[whutfles]

Well guess I'll have to get into my loom and see what's in it. What model do you have?

[kencare]

Originally Posted by whutfles

well guess i'll have to get into my loom and see what's in it. What model do you have?

2005 3500rl

[kencare]

My bad its a 2008 3500RL pulled by 2005 GMC 2500