Momentum 25G Furnace over-temp?

[Dan P]

2021 Momentum 25 G. We have only been out 3 times. The first was overnight in the dealers lot. The furnace quit twice requiring us to cycle the T-Stat off and on to restart it. Then on a bigger shake down, at 29 degrees outside and the T-Stat set to 68 the furnace would only make it to 64 and it ran continuously. It needed recycling on that trip too. The kitchen area register temp reaches 130 degrees, the bathroom 140, (will burn your bare feet) and the bedroom 120 degrees. I don't know how to measure flow, but it may be slightly less than my old weekend warrior or other trailers I've had. It had been suggested that it may be a return air problem. Removing the access panel and leaving the cabinet door open does not effect the flow or temperature. All the exposed ductwork is free and clear and not kinked.. The cabin seems to be sealed well and I can't detect any cold drafts coming in anywhere. I suspect the furnace has a 150 degree over temp limit switch that's tripping and causing the need for the restarts. I'm stuck on the thought that it's an airflow issue. Are there speed taps on the blower? Got any tips before i start a ticket? I'd much rather take care of it myself is possible.

[TucsonJim]

2021 Momentum 25 G. We have only been out 3 times. The first was overnight in the dealers lot. The furnace quit twice requiring us to cycle the T-Stat off and on to restart it. Then on a bigger shake down, at 29 degrees outside and the T-Stat set to 68 the furnace would only make it to 64 and it ran continuously. It needed recycling on that trip too. The kitchen area register temp reaches 130 degrees, the bathroom 140, (will burn your bare feet) and the bedroom 120 degrees. I don't know how to measure flow, but it may be slightly less than my old weekend warrior or other trailers I've had. It had been suggested that it may be a return air problem. Removing the access panel and leaving the cabinet door open does not effect the flow or temperature. All the exposed ductwork is free and clear and not kinked.. The cabin seems to be sealed well and I can't detect any cold drafts coming in anywhere. I suspect the furnace has a 150 degree over temp limit switch that's tripping and causing the need for the restarts. I'm stuck on the thought that it's an airflow issue. Are there speed taps on the blower? Got any tips before i start a ticket? I'd much rather take care of it myself is possible.

Hey Dan. I'm in agreement with you that it's probably hitting the over temp limit. And I'm thinking along the same lines that it may be an airflow issue. Just for grins, what furnace model do you have? Another question is what air conditioner make and model do you have? If you have the Furrion AC, the only sensor for the thermostat is inside the AC plenum. But this usually only causes the inside of the RV to get really warm as compared to the thermostat setting.

Jim

[Dan P]

Thanks for responding Jim. The furnace is a Suburban SF30Q, AC1 - Coleman 15k btu, AC2 Coleman 13.5k btu. I'm hoping someone has experienced this and has a solution. I've emailed customer support and I'll pass their suggestions along. I consider a furnace bumping into the high temp limit switch repeatedly a hazard. So I'm hoping to get some answers. I was just going to go to Suburban to see if that furnace has multiple taps for fan speed.

[Jlawles2]

Dan, something to check is the outside vents for obstructions. If these are blocked in any way, strange things happen. I would not be surprised if strong winds would not cause issues.

[Dan P]

I thought I'd update the situation.... I've spoken with customer support, was connected to a specialist who was stumped. She sent me a ducting drawing at my request, and said she would contact a person involved in service for an opinion. She also said she wasn't aware that this was a common problem. Since I am 4 hours away from a warranty center she verbally authorized an independent shop to look at it. She promised to get back to me with the service guys opinion and an authorization for independent warranty coverage. That's well over a week ago I believe. No response yet. I think this will be a tough one to resolve because the only time the furnace will have to run long enough to trip the over temp cutout, is in very cold weather, when it's needed the most!. It will be hard to duplicate now that it's warmer.

[GDRV-Emily]

I thought I'd update the situation.... I've spoken with customer support, was connected to a specialist who was stumped. She sent me a ducting drawing at my request, and said she would contact a person involved in service for an opinion. She also said she wasn't aware that this was a common problem. Since I am 4 hours away from a warranty center she verbally authorized an independent shop to look at it. She promised to get back to me with the service guys opinion and an authorization for independent warranty coverage. That's well over a week ago I believe. No response yet. I think this will be a tough one to resolve because the only time the furnace will have to run long enough to trip the over temp cutout, is in very cold weather, when it's needed the most!. It will be hard to duplicate now that it's warmer.

Dan P , can you please let us know who you chatted with in support? Also, your VIN would be helpful so that we can check in to this for you. We definitely want to make sure we get you the best, most accurate info. With the way the RV world is right now, we do get stumped from time to time. We have never seen this type of situation where we have had to substitute and change so many products because of availability by vendor. Hope you understand we are doing the best we can!

[Dan P]

Thank you Emily.. Vin 22M1214662. Case 103453. I've had a good conversation with Stephanie Butler after the previous writing.. She got a couple things moving along and I was happy with my conversation with her. She got me the new style rubber / plastic bumpers for the rear door closure binders and promised to get me a couple additional legs for the couch that twists so bad with only one leg in the center.... I haven't seen them yet... For the furnace she has authorized a local shop to do repairs. I picked a place with a certified Suburban tech. I have an appointment with them later this week. I'll post the results. It did do it again last week. We woke up cold with the heat symbol flashing on the T-Stat. Switched to off and back on it fires at the first ignition cycle every time. With the 140 degree temps, and no blockages in the vents I'm convinced it's an over temp fault. Perhaps a bad relay with high resistance to the fan motor, or a bad fan motor is my guess. It just doesn't blow as hard as my older trailers and it doesn't heat as fast either, even considering the excessive temps at the registers... Thanks for you concern. If I can get my furnace to work well and if I could get GD to officially recognize and correct the fresh water siphon problem I'd have a dandy trailer! Thank you...

[Country Campers]

GDRV-Emily

Please see above.

Brian

[Dan P]

Today's update. The unit is in a shop now with a certified Suburban tech. He concludes that the ducting requirements don't meet Suburban's design requirements and suggests one more 4 inch duct is required. A quick call to GD and the advisor tells me this is not unheard of... Now we wait for for emails to go back and forth between shop and GD.. I know the additional register will go in the kitchen.... Oh,,, that will be toasty while the bedroom is already a bit chilly unless the bathroom door is left open.

[Dan P]

One more update.. GD sent me a copy of the ducting plan for the 25G. There are 3 4 inch ducts plus a 2 inch for the tanks. I downloaded the tech manual for the furnace, 3 4 inch ducts are required. Suburban's design requirements have been met. This is really frustrating. Perhaps it's more of a Suburban issue than it is a Grand Design issue.

[Dan P]

One more update. I've had the 25G with a Suburban certified tech and he disagrees with Suburban's design requirement for 3 4 inch ducts. He added one more run along the back of the kitchen cabinets with the register in the "hallway", pretty close to under the thermostat. This isn't a GD shop. They swear that they have authorization to do the work under warranty. GD says they have no record of authorizing the work. I asked the shop not to do anything without written authorization. They went ahead anyway promising they would eat it if GD refuses. Temps here in SE WA are in the high 60s and low 70s during the night so I won't be able to test it until this fall.

[Dan P]

This is a never ending story. Adding a duct didn't resolve the problem. The register temps are lower now and the heat actually seems better distributed, but it still locks itself out... I was awake this time to hear the fan come on for about 8 seconds. I couldn't hear the click of the gas solenoid, the fan shuts off and it's locked out... so it's not an over temp situation after all... I called to see if GD would help me get priority in a shop... No luck the closest shops are booked way out. I wrote again and was authorized to go out of network as before. I called the local shop that did the extra register, no they don't want it back because GD hasn't paid them. I suspect they work they did wasn't authorized. I'm feeling alone now... I pulled the cover and the sail works fine and with good force on the switch. The switch tests fine repeatedly.. That leaves the board. I've been an electronic tech for years so I'm not afraid of it. But I could use some advise.. Are people turning to the Dinosaur board for a replacement? The rivets in the board are in a slot. Is there a release or anything keeping it captive? And finally, are people having luck changing the board without removing the furnace? Any tips are appreciated.

[Phil N]

Dan P Has your issue been resolved? I have a 2021 28G that has the SF 30Q. I just got back from a trip today and this was the first trip I used the furnace. I experienced the same issues you mentioned above. I did find that setting the T stat 65* or higher I would have to cycle the T stat off and on. That was waking up at 3:30 in the morning to find out the furnace was not cycling. At 64* it cycled off and on through out the night with no issues.

[Guest]

elranas What was the solution to your over temp condition? This may help solve Dan P's issue.

Jim

[Dan P]

I checked the sail and sail switch multiple times without a failure. This led me to believe that it had to be the control board. I ordered the Dinosaur board but it didn't come before a 7 day outing. In that 7 days it only failed once where it had been failing nightly. This leads me to believe that a wire isn't crimped well, or there is a cold solder joint on the original board. The new board tests well now that I have it in but I have no real experience with it over night. So a recap, it was not an over-temp, and the additional duct didn't help other than it doesn't burn my feet in the bathroom any more. I was fortunate enough to be awake one night and it didn't ignite after about 8 seconds of fan. I suppose it could be an igniter adjustment problem, but I'm pretty convinced it's either a bad wire connection or was a bad board. I may not know until next season for sure. Cheers all.