Gateway and EOL Access

[Done Workin]

After replacing the sail switch, furnace control board and battery on my 2019 Alpine 3700FL, I spoke with ASA. I have two rooftop A/C units (Dometic) and a Dometic (DFMD35121) furnace. ASA provided me instructions on how to verify if the end of line (EOL) resistor is present in the gateway. My issue is I cannot find the gateway to verify. I removed the air return vents (#1 and 2 A/C) inside the coach as the instructions show, but all I see is the ducting. Do I have to go on top of the unit to access the gateway on this model RV? Any help is appreciated.

[ChuckS]

Originally Posted by Done Workin

After replacing the sail switch, furnace control board and battery on my 2019 Alpine 3700FL, I spoke with ASA. I have two rooftop A/C units (Dometic) and a Dometic (DFMD35121) furnace. ASA provided me instructions on how to verify if the end of line (EOL) resistor is present in the gateway. My issue is I cannot find the gateway to verify. I removed the air return vents (#1 and 2 A/C) inside the coach as the instructions show, but all I see is the ducting. Do I have to go on top of the unit to access the gateway on this model RV? Any help is appreciated.

Yes.. I am fairly well versed on Alpines.. I own one.. The GATEWAYS for your roof A/C units are laying inside the Evap coil Cover on each roof A/C unit. To get access you have to First remove the plastic outside cover..

I am Guessing your 2019 has the Dometic NXT series roof A/C units.. toward the front of each unit you will have another cover to remove.. Once you remove that cover look down where the EVAP coil is into the duct and you will see the black plastic box ( gateway ) with wires attached..

I gather your issue is with the FURANCE and it wont RUN? if it wont come on at all you need to check the two BLUE signal wires on the Zone ( Usually Zone 1) on the control board and gateway to make sure they are making good connection otherwise furnace will never turn on

** Nothing that you need to access for your issues is from within the inside for the Control boxes and gateways for each roof A/C unit

[ChuckS]

Also watch this vide from my Alpine YouTube Channel... It will open your eyes a bit and will also show you where the control box and gateway are located.

https://youtu.be/-QJTxSDZRWE

** NOTE - the EOL resistor you are looking for will be in the LAST Zone ( usually front A/C unit ) plugged into the gateway.. Small white plug with a 120 ohm resistor in place..

To verify simply measure with your mulitmeter across the Green and Yellow wires and you should read around 120 ohms indicating the EOL resistor is in the circuit..

IF it WAS NOT there then you would have had all sorts of issues with your HVAC system long before this

[Done Workin]

The furnace blower comes on and then the burner kicks in a little bit afterwards, but the burner cuts off, restarts, and short cycles. Sometimes the blower will remain on but the burner will cycle on/off up to 17 times before finally lighting and staying lit.

Sometimes it (blower and burner) literally shuts off for a couple of seconds then comes back on.

The RV repair guy has suggested just placing the furnace on its own thermostat and by-pass the INCommand system. This involves cutting the blue wires, which I am not too keen on doing.

I have also thought of totally replacing the furnace ($1500). Any suggestions if you believe the EOL resistor would have to be in place. I had no isses with my AC units all summer.

[RollaMo]

Originally Posted by Done Workin

Any suggestions if you believe the EOL resistor would have to be in place. I had no isses with my AC units all summer.

If you are not having any issues with the AC unit, then it is highly unlikely that EOL resistor is your issue.
As Chuck mentioned, without it you would have had issues before this.

[Done Workin]

Sir:

Thank you. I spent some time on the phone with a Keystone Tech rep and we went through some troubleshooting. They pointed me to the furnace and gave me a contact number for Dometic. So the chase goes on. Other than the sail switch and control board, any other suggestions for the furnace?

I tested the gas flow and changed the battery so those are good.

[chuckster57]

How did you test the gas flow? And where?

[ChuckS]

Edited post…

The EOL will not what so ever be your problem..your issue is that when the Atwood furnace fires off and tried to run the flame sensor is not seeing a reliable flame source hence the issue ..

I would pull that burner chamfer out and clean it and the clean ignitor and flame sensor and gap to 1/8 inch

The only other item in the circuit that would cause furnace to cutoff like you are staying is the Hi Limit switch.. but it is good during the start up sequence and the gas valve and ignitor are trying to do their job.from what I’ve read in your post,

Additional thought .. on the Atwood furance on the outside shiny metal cage is a black switch. If the contacts are intermittent this will kill the 12 volt feed to the control board..I would cycle that switch several times and retry operation