Issue with RM 2652 Fridge on Propane

[mduff]

Appreciate your thoughts on what may be causing our fridge to not work on propane. First its the Dometic RM2652 with an integrated ignition. We're dry camping and running a generator to maintain our battery each day, and using propane overnight and most of day to keep the fridge cold. Note the the fridge is okay on 120v - running generator with fridge setting on auto.

I've addressed the possibility of low voltage, battery reading 13v+, and tried the fridge on propane (AUTO/GAS Mode Selector Button set to gas) while running the generator. Confirmed at the main terminal (for fridge) that we have 13v+.

Propane is working fine for the stove, and water heater. When attempting to light I get a faint smell of propane at the fridge. However tonight I'm removing the orifice to clean (with alcohol); suspect that this would create a poor flame versus no propane...

Checked the solenoid, continuity good, 47ohms, and 13.4v read when the unit is in trial-for-ignition.

Measured 13v+ across the thermofuse and at J4 on the circuit board.

Suspect the igniter/electrode as there is no sparking at the electrode tip (viewed directly with covers removed). Unable to disconnect as suggested in the service manual for units with a separate igniter, high voltage cable/electrode are one unit, and igniter is integrated (noted on page 17 of the Dometic Service manual not to run disconnected). Tonight I'll review the grounding of the electrode, though recently had this apart and no visible corrosion.

Any thoughts appreciated.

Thanks
Mike

[Herk7769]

Things to check:

1) You say it is the RM-2652. Is it windy? There is a recall on RM-2652s to add a metal shield and stack over temp sensor (see photos of fridge to see mod). If the recall was not performed, wind can keep the flame from lighting and/or blow out when lit.

2) Clean out stack. Bug nests (spider/wasp) in the flue can cause an over rich mixture in the combustion chamber and not allow ignition.

3) Examine spark gap. A bent electrode can prevent the DSI from igniting the gas.

4) After 3 start attempts, the control board will "LOCK OUT" and the check light will come on. You must turn off the fridge to reset the board

5) Battery voltage must be above 11.5 volts for the control board to function and the solenoid to open. 13+ volts is "charging voltage" and should only be that high when the generator is running (and shortly after you shut it down while the surface charge gets dissipated). What is the battery voltage an hour AFTER you shut the generator off?

[mduff]

Originally Posted by herk7769

Things to check:

1) You say it is the RM-2652. Is it windy? There is a recall on RM-2652s to add a metal shield and stack over temp sensor (see photos of fridge to see mod). If the recall was not performed, wind can keep the flame from lighting and/or blow out when lit.

2) Clean out stack. Bug nests (spider/wasp) in the flue can cause an over rich mixture in the combustion chamber and not allow ignition.

3) Examine spark gap. A bent electrode can prevent the DSI from igniting the gas.

4) After 3 start attempts, the control board will "LOCK OUT" and the check light will come on. You must turn off the fridge to reset the board

5) Battery voltage must be above 11.5 volts for the control board to function and the solenoid to open. 13+ volts is "charging voltage" and should only be that high when the generator is running (and shortly after you shut it down while the surface charge gets dissipated). What is the battery voltage an hour AFTER you shut the generator off?

Thanks Lou for the list.

1) Modification was done. With and without the shields in place no ignition. I'm comfortable with the sound of the fridge starting and running on propane from the outside; we're not getting there. Should add that earlier the week it was running okay. We've been dry camping for over a week and the issue started after about 4 days.

2) I'll check and clean the stack.

3) Confirmed the gap, we're good on that.

4) Good point to confirm. We have been cycling the power on the fridge each time, allowing a period to clear the board, e.g. 10 seconds, before attempting, and following receipt of the check light.

5) Battery voltage read over two (2) days was 12.59v, and 12.55v (checked in the morning), running the generator in the evening to charge. Also have a 40w solar panel that I set up on sunny days; it's marginal what it provides to charge, suspect more maintains the battery.

[Herk7769]

Since you smell gas (outside) when it is trying to light and the gap appears correct, mixture is the only remaining possibility. If the stack cleaning does not help; it should fix it!

DO NOT put anything in the orifice. Even a slight enlargement can result in an uncontrollable fire. Wipe the end with an alcohol swab and that is it.

Beyond that... I don't know.

[mduff]

Originally Posted by herk7769

Since you smell gas (outside) when it is trying to light and the gap appears correct, mixture is the only remaining possibility. If the stack cleaning does not help; it should fix it!

DO NOT put anything in the orifice. Even a slight enlargement can result in an uncontrollable fire. Wipe the end with an alcohol swab and that is it.

Beyond that... I don't know.

I'll get at the stack tonight. Is there a trick to cleaning the stack? The users manual provides; "Remove the wire and flue baffle from the top of the flue tube. Using a flue brush, clean the flue from the top..." How do you get access to the top?

Understood regarding the orifice. Will follow the service manual - "The orifice is cleaned by using an alcohol based solvent. Soak the orifice for approximately 1 hour and allow to air dry. Don’t insert anything in the center of the orifice it will harm the man-made ruby."

Any thoughts on the electrode; could this be the issue and not firing? Do these normally fail?

[BarryD0706]

Originally Posted by mduff

...
Suspect the igniter/electrode as there is no sparking at the electrode tip (viewed directly with covers removed). Unable to disconnect as suggested in the service manual for units with a separate igniter, high voltage cable/electrode are one unit, and igniter is integrated (noted on page 17 of the Dometic Service manual not to run disconnected). Tonight I'll review the grounding of the electrode, though recently had this apart and no visible corrosion.

You see no spark and you hear no spark. It's not a gas or orifice issue. Given that the gap and voltage are good, it sounds like you need to replace the electronic igniter (board), unless there is a fuse there that is blown.

[mduff]

Originally Posted by BarryD0706

You see no spark and you hear no spark. It's not a gas or orifice issue. Given that the gap and voltage are good, it sounds like you need to replace the electronic igniter (board), unless there is a fuse there that is blown.

Thanks Barry

Gulp! The igniter on our unit is integrated on the lower control board for the fridge. The electrode and high voltage cable is replaceable and may be ruled out with a replacement first. There is a 3a fuse that I had ruled out, however will double check as well. Also I'm going to clean the stack as suggested by Lou.

[Herk7769]

Before removing anything, I would get a garden hose and shove it in the combustion chamber and flush out any debris. Compressed air can also be used but I would use a low pressure to avoid damaging the electrode.

[roanmountaincampers]

Mine would not ignite. Electrode was touching combustion chamber causing it to short out.

[BarryD0706]

One more thought. The burner has to be grounded in order for the spark to jump to it. If the part right below the electrode wasn't grounded (or was extremely corroded) this could also cause the problem. I suggest using your ohm meter to verify a good ground at that point.
(A very corroded electrode would also be a problem.) These can be cleaned with sand paper if need be.

[mduff]

Originally Posted by herk7769

Before removing anything, I would get a garden hose and shove it in the combustion chamber and flush out any debris. Compressed air can also be used but I would use a low pressure to avoid damaging the electrode.

I'll get the TT home on Sunday and get this cleaned. It's a good maintenance step in any case. Also have an inspection camera there to visually check.

[mduff]

Originally Posted by BarryD0706

One more thought. The burner has to be grounded in order for the spark to jump to it. If the part right below the electrode wasn't grounded (or was extremely corroded) this could also cause the problem. I suggest using your ohm meter to verify a good ground at that point.
(A very corroded electrode would also be a problem.) These can be cleaned with sand paper if need be.

Good thought Barry, thanks. I read under the LP section that a bad ground would cause erratic behavior. I had cleaned the grounds near the lower control board previously (last month), however missed the ground to the burner area. I disassembled the burner/electrode last night and cleaned up all the touch points and cleaned the ground cable (at the burner end) that comes from the point near the control board - dielectric grease on all connections. Also soaked the orifice to cover that possibility.

Good news, unit fired up on propane and ran through the night, bad news had a check light come on during breakfast (battery reading 12.55v). We ran the generator for a period and retried the propane; lit once again. Leaving it on propane for now hoping that the earlier check light was 'normal' and resetting (the fridge) and allowing a period of cooling (while running on 120v off generator) for the propane components is the answer.

From this I know that the control board/igniter are working, and the electrode is okay. Certainly may have an intermittent issue on the board and if the problem continues may replace the control board to eliminate it.

[BarryD0706]

Most excellent!

If the error code comes on again, it would be good to know how it's failing. Reset the fridge and then go outside and watch while someone turns it on inside. If the burner lights and then goes out after a few (5?) seconds, it's time to take some sandpaper to the electrode (which is also the flame sensor).

[mduff]

Originally Posted by BarryD0706

Most excellent!

If the error code comes on again, it would be good to know how it's failing. Reset the fridge and then go outside and watch while someone turns it on inside. If the burner lights and then goes out after a few (5?) seconds, it's time to take some sandpaper to the electrode (which is also the flame sensor).

I was hoping to post that this was resolved, however...

We cleaned the electrode as a preventative measure, and removed the burner tube and soaked it in alcohol to clean (with a light application of a brass brush by the slots). From the Service Manual "If the burner does not have a good ground it can cause erratic gas operation. The electrode sparks to the burner tube and a erratic ground will cause erratic gas operation."

The frustrating part is we reset the fridge and it now lights 'consistently' though will not continue to run continuously; I define this as 'erratic' . We're unable to get a good sense for "good to know how it's failing"; we hear the solenoid clicking followed by clicking (of the electrode) then the propane ignites, we leave it and it operates correctly for some hours before failing.

We started a log. The fridge ran (on propane) from 11p Saturday evening to 6:30a Sunday - check light. Restarted at 8a Sunday and it ran until 2p - it checked some time on the trip home. Last evening (Sunday at 10p) we started the fridge on propane (after reassembly) and it ran fine until 11a today, then a check light. Tonight I'm going to review steps as it feels that I'm getting close! Will likely disassemble where the burner assembly mounts to the supporting structure and ensure no corrosion between these points.

Now that we have access (to the Internet) I will get some pictures posted to help others understand the referenced items.

[mduff]

Originally Posted by BarryD0706

Most excellent!

If the error code comes on again, it would be good to know how it's failing. Reset the fridge and then go outside and watch while someone turns it on inside. If the burner lights and then goes out after a few (5?) seconds, it's time to take some sandpaper to the electrode (which is also the flame sensor).

Spent tonight checking my work to date. Reassembled the pieces and with battery only tried the fridge on Auto, fired up, solenoid clicked followed by flame within seconds. Turned off the fridge and retried 10 times, same result fired up on propane. Switched the fridge to LP (why not...) and turned on the power, solenoid clicked and within seconds flame. Three (3) attempts no problem. Fourth attempt, solenoid clicked then nothing - silent, no clicking, etc. I could hear the gas entering the burner. Retried a number of times with no success, even switched back to Auto with no luck; through all these tests this was done on battery.

Any thoughts before I replace the lower control board?

[BarryD0706]

And if you go back on generator or shore power?

[mduff]

Originally Posted by BarryD0706

And if you go back on generator or shore power?

Connected shore power and fridge switched to AC; fridge was set to Auto. Are you wondering if it would fire on LP when connected to shore power?

[BarryD0706]

Originally Posted by mduff

Connected shore power and fridge switched to AC; fridge was set to Auto. Are you wondering if it would fire on LP when connected to shore power?

Yes, sorry for not being clear.

[mduff]

Originally Posted by BarryD0706

Yes, sorry for not being clear.

No worries, appreciate your assistance.

More data...

On shore power, fridge set to LP, attempted five (5) times, solenoid clicked, could hear gas, no other sounds, did not light.

Turned off shore power, fridge set to Auto, tested three (3) times successfully, fourth attempt failed, solenoid clicked, could hear gas, no other sounds. Further tests failed, attempted three (3) more times.

[BarryD0706]

I sure think its the board at this point, but as you said earlier, replacing the electrode first is a cheap thing to try. Let us know how it goes, and good luck!