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How do I remove and clean the hydro flame sensor? 2021

How do I remove...

How do I remove and clean the hydro flame sensor? 2021 forest river Crusader. Dometic dfmd 35131 heater

Mechanic's Assistant: Which particular sensor are you asking about? And have any trouble codes been triggered?

Heater blower kicks on heater ignites for about 3 seconds then shuts off consistently every 10 seconds

Mechanic's Assistant: Are you fixing your Kicks yourself? What have you tried so far?

Trying out in the woods. Checked the sail switch so far

Mechanic's Assistant: Is there anything else the Mechanic should know before I connect you? Rest assured that they'll be able to help you.

The heater is my issue at the moment

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Answered in 1 minute by:
1/29/2022
RV Mechanic: Robert, RV Mechanic replied 8 months ago
Robert
Robert, RV Mechanic
Category: RV
Satisfied Customers: 24,124
Experience: 23 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.
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Hi! Welcome to JustAnswer. Thank you for contacting us about your RV. I am Robert and will be assisting you today. May I please have your name?
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Customer reply replied 8 months ago
WillHowdyTrying to locate, remove and clean the flame sensor
RV Mechanic: Robert, RV Mechanic replied 8 months ago

Hi will! Sorry to hear you are having issues with your furnace, I would like to go into some details for you on this of the possible causes. Just to confirm, the furnace is actually firing off for 3 seconds then shutting down? You are getting heat out the exhaust?

This could be other things besides the electrode. The electrode sparks the flame and acts as the flame sensor.

Robert

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Customer reply replied 8 months ago
it kicks on for about 3 seconds then shuts off and ignites again roughly 10 seconds laterBlower stays goingHeat does come out of the exhaust
RV Mechanic: Robert, RV Mechanic replied 8 months ago
I would like to give you some other items to look at before you have to remove the furnace. I want to provide you some troubleshooting as if this came into the shop. Please allow me several mins to type a response, lots to cover.

Robert

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RV Mechanic: Robert, RV Mechanic replied 8 months ago

The key is the furnace is trying to light off and is sparking.

For this condition the propane pressure, circuit board, high limit and electrode are suspect.

We have to assume your propane pressure is good, I do understand if the other propane appliances are working but that does not mean the pressure is off, each appliance can act differently. In the shop I would hook a manometer to the system to read the pressure. What you can try is go to the propane tank and shut the supply valve then slowly open it up. Sometimes if the supply valve is opened to fast the regulator can lock up and you may not get the proper pressure, slowly open the valve and then run a stove burner for several mins.

After the fan kicks on make sure the DC battery voltage is not going under 12 volts, if the voltage was dropping off it can cause issues with the sail switch, you should have over 13 volts DC if you are plugged into power.

The circuit board on the furnace is also suspect, these boards can fail. Most good mobile RV techs will have a special board tester and can tell if the board is bad or not. IF the board checks out good then you are looking at the high limit and electrode. The high limit sits on the burner, it is a small round disc, you should have continuity through.

To get to the electrode you may have to pull the furnace and work with it on a bench, not to many RV's have outside access panels anymore which makes everything difficult to work on. The electrode will sits where the gas valve assembly is located on the furnace, you would not isolate the propane at the tank on the RV and disconnect the gas valve assembly line and then pull that out to get at the electrode. See picture below, #6 is the electrode and #5 is the gas valve assembly.

IF you have more questions or concerns please feel free to contact me, I am around daily and respond when I can, sometimes I am helping others or away from my desk, I try to respond back as fast as I can.

Robert

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Customer reply replied 8 months ago
I want to try and pull the electrode and clean it. Do I have to remove the entire gas valve to get the electrode out? I do have an access panel on the outside. I have checked the sail switch and have new propane.
RV Mechanic: Robert, RV Mechanic replied 8 months ago
normally to get to the electrode you have to remove the gas valve assembly and when that pulls out you should have access to the electrode. Should be a flange in that area with some screws and you pull it out, if you look on the parts breakdown the flange is to the right of the electrode the nozzle for the gas valve sits right next to that electrode. You are lucky if yours has an outdoor panel, normally this is not the case.

Robert

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Customer reply replied 8 months ago
Well I am still under warranty and my concern is voiding that if I attempt to remove the entire gas valve.
RV Mechanic: Robert, RV Mechanic replied 8 months ago

IF you are still under warranty do NOT touch it, if they see you have been messing with it you can void the warranty, I have seen this happen over and over in the past. My suggestion would be to let the dealer look at it and document the problem for any future problems. In the mean time if you are plugged into a 30 or 50 amp service you could use a small portable heater, you would just have to manage what is on the circuit, you would not want to turn on the microwave, hair dryer etc with a portable heater. I under stand this is super frustrating but trying to be helpful on how you might be able to get some heat if the furnace is down.

Robert

Robert
Robert, RV Mechanic
Category: RV
Satisfied Customers: 24,124
Experience: 23 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.
Verified
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Experience: 23 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.

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