2024 310GK Furnace works on batteries/Cuts off when on shore power

[ajg617]

Here’s a pic of my furnace. In looking at it I’m realizing there’s one duct running to the island not two. Must go into a box with two coming off on either side. Per the furnace install manual there should be a minimum of 4 4” ducts coming off the furnace and the one 2” doesn’t count. I’ve got three unless one is hidden and I don’t remember. If so that could cause an overheat as well.

This is ours. The hutch was a huge problem as it was the shortest and easiest flow for the furnace. The hutch was where the majority of the flow came out (shortest route from furnace) into the living area. I replaced the register with one that could be adjusted.

[Boxer1200]

I may try that once I get this sorted. Great idea. Do you have one or two ducts extending to the kitchen island?

[ajg617]

I may try that once I get this sorted. Great idea. Do you have one or two ducts extending to the kitchen island?

One duct going to both ends of the island. Very little air coming out of that - most coming out of the coffee bar.

[Scott'n'Wendy]

I’m leaning towards this being an overheat issue. My reasoning is this. One, very little air flows from the island vents or the bathroom vent by the toilet.

While pinched hoses or somehow blocked/restricted can cause overheat and shutdown, that doesn't fit the symptoms of working fine off battery but not shore power. Have those symptoms changed?

[Boxer1200]

While pinched hoses or somehow blocked/restricted can cause overheat and shutdown, that doesn't fit the symptoms of working fine off battery but not shore power. Have those symptoms changed?

That is true. Maybe I’m just grasping at straws here. Last night for a little light reading, I read the entire service and training manual, and it all points to thermal shutdown. Here’s an excerpt from that.

If during the heating cycle, the limit switch circuit opens and remains open for 5 minutes, the module board will go into lock out and shut down the blower motor. If this occurs, the thermostat will need to be reset for the furnace to operate.

This perfectly describes my scenario. I suspect there is so much heat trapped in there I’m still feeling warm air from the vents right up to the point the fan shuts off. Again, you can’t even touch the furnace without burning a finger after shutdown.

The last morning of the trip since I knew we didn’t the need the microwave I flipped the breaker at the pedestal so I was on batteries and this time it shutdown prior to reaching temp. So that debunked my initial results. It did run 26 minutes. So a bit longer but still wouldn’t reach the requested temp.

Out of town for work now, but this weekend I may detach a duct on the furnace and see what my results are. Probably pull the island duct since it’s the weakest on the output end. Additionally I’ll stick a meat thermometer or something in the duct to see if the temp changes at all.

[howson]

Boxer1200

I agree with the thermal overheat hypothesis. However, what set this thread off on a tangent is in the title itself--the furnace works fine on battery power but fails on shore? Is this still true or upon subsequent troubleshooting found that was incorrect?

[Scott'n'Wendy]

Boxer1200

I agree with the thermal overheat hypothesis. However, what set this thread off on a tangent is in the title itself--the furnace works fine on battery power but fails on shore? Is this still true or upon subsequent troubleshooting found that was incorrect?

Yup..nothing wrong with introducing new evidence that contradicts the first position. I always say 'Never get Married to your First Idea' when it comes to troubleshooting.
There are reports of underbelly air ducts being compressed by other components and that may be your case where the furnace does not have free enough ducts to move the heated air out. Return air is needed but pretty hard for that to be inadvertently blocked so probably not that....but make sure they are not blocked I suppose it would be possible for there to be a fan problem...but the sail sw would probably detect that.

[ajg617]

There is a limit switch and module board on the Suburban water heaters also. These are known failure points according to two mobile techs (one GD) that I talked to when I couldn't get the heater to light on propane. The module seemed to be the worst offender.

[Boxer1200]

Boxer1200

I agree with the thermal overheat hypothesis. However, what set this thread off on a tangent is in the title itself--the furnace works fine on battery power but fails on shore? Is this still true or upon subsequent troubleshooting found that was incorrect?

I did disprove this theory while at the campground this past weekend. Off shore power and it quit this time. Don’t get why that worked the way it did previously. My apologies for the tangets.

ajg617 The limit switch was actually replaced as soon as this all started the day after purchase. Supposedly the dealer has checked out the board, sail switch etc by removing and bench testing. They say they ran it for hours in the trailer but I know that to not be true as it’s not possible. No tech is going just sit in the trailer for long enough to see this happen.

I made an appt with a reputable independent mobile tech co and I’ll drop it off at their shop Friday. I figure if I’m paying someone directly they’ve got a vested interest in getting this right. Not just rushing through it. Plus, no back and forth on warranty with GD and I can speak to the tech directly. It’ll cost me a few bucks but I don’t trust the dealer to work too hard on this.

[Reacher]

The SF 35 blower should draw 8.4-8.5 amps. If your voltage is correct and you're not seeing proper amp draw then the motor may be your problem.

[Boxer1200]

I’ll definitely follow up on here after these other techs take a look at things. Suppose I’m lucky this is the biggest issue with this new trailer, but it sure is driving me nuts since I can’t solve it. Stay tuned.

[Boxer1200]

Update...The indy shop, unlike the dealer has confirmed there is indeed a problem, but they're stumped as of now on what it is. Everything checks out good except the furnace won't do what you ask of it. They're working with Suburban to try and figure it out. Supposed that's better then throwing parts at it, but we'll see. I'll probably prod them more today asking about what they've tested on the electrical side, and to double check the ducting. I'd rather not have the coroplast dropped or cut unless absolutely necessary, so I'll have them check from above under the island panels first.

[Boxer1200]

A little update. Took this to an independent rv repair shop. Decided if I’m paying out of pocket someone will be more willing to put some effort in.

They found a bad board. Added a new board and then some issues still persisted. Found the motor pulling 12 amps. Should max out at 10. It keeps climbing, then amps out and shuts the whole unit down. So getting a new blower motor now. They’ll also check the gas solenoid since it appears there’s multiple fail points. I’m certain someone at the GD factory dropped it or crushed it because the cage is bent up. My dealer didn’t seem bothered by the bent up cage so didn’t dig deep.

Hopefully this fixes it. I’ll report the finality of it soon I hope.

[ncitro]

Glad you are seeing some progress. I am surprised with that many failures and the bent up cage they did not just replace the whole unit.

[Country Campers]

A little update. Took this to an independent rv repair shop. Decided if I’m paying out of pocket someone will be more willing to put some effort in.

They found a bad board. Added a new board and then some issues still persisted. Found the motor pulling 12 amps. Should max out at 10. It keeps climbing, then amps out and shuts the whole unit down. So getting a new blower motor now. They’ll also check the gas solenoid since it appears there’s multiple fail points. I’m certain someone at the GD factory dropped it or crushed it because the cage is bent up. My dealer didn’t seem bothered by the bent up cage so didn’t dig deep.

Hopefully this fixes it. I’ll report the finality of it soon I hope.

Glad you are making progress. You might want to call Grand Design with your issue and the path you have taken to get it repaired. They may help you out or maybe not, worth a call though I think.

Brian