Need Advice with Dometic Referigerator RM-2807 Malfunction

[bobinyelm]

I have a '96 BigFoot T/C with a Dometic RM-2807 3-way fridge that will not operate on GAS.

If I just select AUTO, it will click to GAS and after 45 seconds issues a CHECK message. During this period, I hear NO "snapping" of the gas igniter.

If I use a lighter during that 45 seconds, the gas flame ignites and the fridge stays lit.

That makes me think either the main circuit board is not supplying the igniter module with 12v to make it work, or the igniter itself is bad.

I looked up the circuit at http://bryantrv.com/docs2/docs/domser.pdf

Here is an instant link to just the electrical diagram: http://screencast.com/t/hyrjRWSFnU

It appears that the igniter is supplied from Terminals 4 Grn/Yel wire and a blue wire in a connector C3.

I would imagine that if I never see 12v present between Term 4 Grn/Yel wire, and C3 that the board is bad, and if I DO see 12v there for the 45 second ignition cycle, and I have no spark, then the igniter module is bad?

Could anyone offer their input on my problem and verify my reasoning?

Thanks,
Bob

[Chris_Bryant]

bobinyelm wrote:

Chris Bryant wrote:
The igniter will stop sparking itself when the flame lights- it's made to be powered continuously. There should be a manual shutoff at the valve- I shut that off to verify igniter operation.

Since the igniter is now wired to be powered when the gas solenoid is powered, what stops it from sparking when the flame is burning? It's no longer turned off by the thermocouple in the modified wiring circuit.

Just curious
Bob

That's built in to the igniter module-when it senses a flame, it stops sparking. It also pulses a 12 volt signal to the third (unused center) terminal while it is sparking. On old models, the main board used that to let it know it was lit. New models it is unused.

It's just a much faster way to relight the flame if it blows out. Before, the flame would have to be out long enough for the thermocouple to drop to ~15 mv. By this time, the flame had been out for a bit, so it had a fair amount of LP to give a nice whoosh when the igniter fired again.

[bobinyelm]

Chris Bryant wrote:
The igniter will stop sparking itself when the flame lights- it's made to be powered continuously. There should be a manual shutoff at the valve- I shut that off to verify igniter operation.

Since the igniter is now wired to be powered when the gas solenoid is powered, what stops it from sparking when the flame is burning? It's no longer turned off by the thermocouple in the modified wiring circuit.

Just curious
Bob

[Chris_Bryant]

The igniter will stop sparking itself when the flame lights- it's made to be powered continuously. There should be a manual shutoff at the valve- I shut that off to verify igniter operation.

[dougrainer]

bobinyelm wrote:

dougrainer wrote:
1996---Take the cover off the rear main control module. IF the Epoxy resin on that module board is beige/tan, the ONLY fix is to replace the Module board. Those years (1993-1997) were the years Dometic had bad module boards that Intermittantly went to check for LP,EVEN IF ON AUTO and not calling for LP. There are 2 parts- The Module (updated) and a Ground Loop harness that needs installed also. If your Module board is NOT beige but greenish in color(meaning that the board is the updated module board), then do what Chris advised. Doug

So if I have a green board (I do), does that mean I also have the updated harness I wonder?

Yes, you do. 20 years ago the harness was sold separately. I just found out yesterday that when you order the Module board for your specific model number, the wire kit comes with the new module. Doug

[bobinyelm]

Chris Bryant wrote:


Other than that- the revised wiring doesn't use the blue wire- it hooks the igniter module to the gas valve, so that it always has power if the gas valve is open. It also moves the grounds around. You can see the revised wiring at http://bryantrv.com/docs2/docs/R704B.pdf.

So you're saying that the revised wiring supplies power to the igniter continuously?

That's what this diagram you linked shows alright: http://screencast.com/t/pJepTtcwEK

Is the igniter module designed to work full-time (any time the gas solenoid is open)?

I read with the old wiring, the igniter is "locked out" if the thermocouple is showing voltage (flame is present), but starts producing sparks if the thermocouple indicates no flame?

I suspect the continuous sparking is probably better if running the fridge on gas while driving and the flame is likely to be blown out frequently?

Looking at this modification inset http://screencast.com/t/VSFqUgCTg it shows changing wires, and mine has the black and yellow wires as in the modification, so the igniter should indeed be active whenever the gas solenoid is activated.

Given that my solenoid was opening (allowing me to manually light the flame), I guess the connection to the igniter was faulty, since it worked after I removed and replaced the push-on spade terminals.

I don't HEAR it snapping when the flame is on, though. Perhaps I'll remove one of the wires to the solenoid (so I can listen for the sparking for the full 45 second period) just to make sure it's operational.

I wonder if my igniter is producing weak sparks-when I tested it, 3/16" spark was about all it would produce when hooked to a charged automobile battery. I wonder how big a spark it should be capable of?

Can you hear continuous sparking (in a very quiet environment) with your outside fridge cover off, the flame on, and your ear near the burner?

Thanks-
I guess the diagram I found was pre-modification.

Bob

[bobinyelm]

dougrainer wrote:
1996---Take the cover off the rear main control module. IF the Epoxy resin on that module board is beige/tan, the ONLY fix is to replace the Module board. Those years (1993-1997) were the years Dometic had bad module boards that Intermittantly went to check for LP,EVEN IF ON AUTO and not calling for LP. There are 2 parts- The Module (updated) and a Ground Loop harness that needs installed also. If your Module board is NOT beige but greenish in color(meaning that the board is the updated module board), then do what Chris advised. Doug

So if I have a green board (I do), does that mean I also have the updated harness I wonder?

[bobinyelm]

dougrainer wrote:
1996---Take the cover off the rear main control module. IF the Epoxy resin on that module board is beige/tan, the ONLY fix is to replace the Module board. Those years (1993-1997) were the years Dometic had bad module boards that Intermittantly went to check for LP,EVEN IF ON AUTO and not calling for LP. There are 2 parts- The Module (updated) and a Ground Loop harness that needs installed also. If your Module board is NOT beige but greenish in color(meaning that the board is the updated module board), then do what Chris advised. Doug

Yes, I had a '96 Lance w/ a tan board that went bad. This one is green.

I removed the igniter module and tested it w/ a battery, and it worked fine. I then checked the wires (black and yellow) to the igniter from the board, and it supplied 12v.

I re-hooked the wires up, and its now working perfectly and lighting the gas immediately. Bad connection? though the push-on spade connectors looked clean.

[dougrainer]

1996---Take the cover off the rear main control module. IF the Epoxy resin on that module board is beige/tan, the ONLY fix is to replace the Module board. Those years (1993-1997) were the years Dometic had bad module boards that Intermittantly went to check for LP,EVEN IF ON AUTO and not calling for LP. There are 2 parts- The Module (updated) and a Ground Loop harness that needs installed also. If your Module board is NOT beige but greenish in color(meaning that the board is the updated module board), then do what Chris advised. Doug

[Chris_Bryant]

The most common failure is of the electrode itself- it becomes internally grounded. You can pull the spark wire from the igniter module and listen for the snap to check. If it is that, often simply removing the electrode, wiping it down with a paper towel soaked in silicone lube, and lightly sanding the wire part will make it operational again.

Other than that- the revised wiring doesn't use the blue wire- it hooks the igniter module to the gas valve, so that it always has power if the gas valve is open. It also moves the grounds around. You can see the revised wiring at http://bryantrv.com/docs2/docs/R704B.pdf.