Dometic Fridge Igniter Won't Stop Sparking!

LandRoutes

Guest
Thought the spare LPG tank was almost full - instead almost empty, in fact it didn't make it through the night with what gas that was left. So this morning I awoke to the Dometic igniter sparking away without a gas supply to quench it. But... once refilled with LPG and all other gas appliances restarted and with the gas flowing, the Dometic igniter did it's duty - pilot flame caught a blaze as prescribed (working flame lit) and stayed on and so did the igniter sparking cycle. In fact the fridge has caught up to working temp and is now 2 degrees with a healthy flame but the sparking of the igniter 'spark plug' continues. The only thing that stops the spark is pulling the fridge fuse - off goes the fridge light and the spark(er) and the flame keeps on blazing, fridge keeps on cooling! Gotta love these simple devices.

Except, I would like to get the igniter to stop sparking as it should when the flame is lit. Does anyone know what senses the igniter to stop sparking once the flame is started? Does the spark plug act as a sensor? I am pretty sure that the thermocouple doesn't get involved because I have had to resort to clipping the gas start knob in the start position to give the thermocouple time to heat up and keep the gas supply flowing but in these cases the spark still stopped immediately after the flame was heard woofing into ignition. (The thermocouple is another issue I have with the system but not the subject of this current problem)

Anyone who knows these 'simple' devices that knows what stops the sparking after ignition who can pass along any advice get's the gold star!

Thanks in advance!
 
It sounds like the button is stuck in.

I am more used to Alde heating, so I'm no expert but occasionally the ignite switch for my Gas Hob does the same thing. I just flick it again and it stops sparking. You might need to strip and clean yours.
 
Firstly, please advise the model number of the fridge so that others who have the same fridge may be better able to help.

I have an older three way Dometic fridge - sorry but I can't remember its model number! - and I had the same fault.

My fridge has a control unit at the rear to which the igniter is connected. There are I think three spade connectors. One of these was corroded. I cleaned all three connections (obviously with power and gas switched off) and the problem was cured.
 
Dometic Fridge won't Stop Sparking

Helpful advice (BTW, I always flick everything as a first course) I will open the cover panel to the igniter in the AM as it is nearing 23:00 here in Turkey. This sounds like a good starting point.

Curiously though; What does send the 'Stop Sparking' signal to the activation/de-activation circuit? and does it so quickly - Inquiring minds really want to know. It will give me something to sleep on if anyone has that answer!
 
LandRoutes said:
Helpful advice (BTW, I always flick everything as a first course) I will open the cover panel to the igniter in the AM as it is nearing 23:00 here in Turkey. This sounds like a good starting point.

Curiously though; What does send the 'Stop Sparking' signal to the activation/de-activation circuit? and does it so quickly - Inquiring minds really want to know. It will give me something to sleep on if anyone has that answer!
Click to expand...

depressing the ignition switch starts the sparker as maingate says if the switch is stuck it carrys on sparking. Under normal operation depressing the starter switch manually opens the gas control valve and sets the sparker going appliance ignites,,,Thermocouple warms up, a solenoid then allows the gcv to remain open and all is good. in the case the flame extinguishes the solenoid closes and shuts the gcv....this principle in its various set ups is how most appliances work not just fridges

channa
 
If its not a stuck igniter button try "resetting" the fridge electrics to solve the problem. Isolate all power to the fridge for about ten minutes. Reapply 12V power and ignite the fridge. If you are still sparking after the gas is lit the spark module may have given up the ghost, it will fail completely if you let it carry on sparking so its better to isolate it if you can. They can get quite hot and melt with the risk of a complete electrical failure.
 
Still Workin On It!

Thanks Guy’s
Here’s an update. I have worked through the suggestions; I removed the cover box on the back of the fridge containing the reignite spark exciter module. It is a very clean space. The 3 wire connecter was in excellent shape with no corrosion. That sort of bummed me out – I had expected a quick fix there.

So I am working back to the thermostat module. The top of the fridge lives under the SMEX 3 hob stove, which I can see leaks escaping cooking fluids, but there is no real sign of any damaging influences from that activity – it’s just somewhat messy under there.

The fridge is an ELECTROLUX model RM 6401L. It is 3/Way with only manual switchover and has an automatic reigniter. You rotate the switch knob to the gas position and the reigniter begins sparking and there is a pilot lamp that flashes right next to the thermostat knob. Then you depress the knob to allow gas flow for ignition of the flame. In a perfect world the flame ignites and the thermocouple opens the gas valve and concurrently signals to shut off the reigniter spark generator. The Gas stays on as long as there is heat at the thermocouple and the igniter stands by for a blow out reignite cycle if necessary.

But… My fridge lights – gas stay’s on and functions perfectly – igniter continues to spark.

So I am questioning a pair of black wires that I have discovered at the thermostat. Two black wires are connected to the thermocouple piston cylinder in the gas connection area of the thermostat. (See Photo 1) I suspected that those wires were shorted when the piston was in the “gas off/thermocouple cold” condition and in an open connection state when the gas is on and thermocouple hot condition. Thus when in the open state there is no ground path to the reigniter and no sparking will occur. So I pulled one wire from its spade thinking the spark goes away – it didn’t – still sparking. I also tried shorting the two wires but with similar result.

Ok. Maybe there is something at the other end of those wires that is failing? The other end of those black wires lead to the other side of the fridge and into the box covering the connections for the mode selector switch knob.

Stumped again. Can anyone take it from here? I would hate to replace the thermostat and find that doesn’t cure the problem.

If it helps here’s pics of the thermostat and switchover module areas.
IMG_3154.jpgIMG_3162.jpg

OOPS! can't get rid of the second attachment, sorry for the double vision.
 

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continual igniter sparking

landroutes............I have exactly the same problem with my dometic fridge, but you can still use the fridge as normal.............to light the gas flame with the igniter, simply ensure the 12v igniter leads to igniter box in the outside bottom (rear of fridge) panel of the van are connected, and press in and hold the thermostat switch and then ensure the gas flame is alight. or light flame as instructed. use your ear or eye right close to the gas exhaust. when the flame is lit, simply unplug the igniter light leads so it goes out. to check when your gas is gone, you have to check your cooker rings next to the fridge, (because your igniter light will be off) and then refill gas and relight as above....steve bristol
 
It sounds to me like the spark ignitor box is faulty, if you remove the lower fridge vent you can see and change it easily enough, from the ignitor follow the thick HT cable back to the box
If you look on here you will be able to find the part number, I had to change mine for the same fault
 
tezza33 said:
It sounds to me like the spark ignitor box is faulty, if you remove the lower fridge vent you can see and change it easily enough, from the ignitor follow the thick HT cable back to the box
If you look on here you will be able to find the part number, I had to change mine for the same fault
Click to expand...

+1. Many of these ignitors are "automatic". The one in my Thetford certainly is. Basically, they sense the flame and start clicking immediately it blows out. I'm not sure how they work but I'm guessing the ionisation from the flame discharges the HT generated by the ignitor unit. They can go faulty and continually click.

Keith
 
before changing the ignition module I would clean the electrode thoroughly with some wire wool as although a dirty electrode will spark and ignite the gas with single electrode systems it also has to complete an ionisation control circuit and the cleaner it is the beter
 
LandRoutes said:
Helpful advice (BTW, I always flick everything as a first course) I will open the cover panel to the igniter in the AM as it is nearing 23:00 here in Turkey. This sounds like a good starting point.

Curiously though; What does send the 'Stop Sparking' signal to the activation/de-activation circuit? and does it so quickly - Inquiring minds really want to know. It will give me something to sleep on if anyone has that answer!
Click to expand...

well you did ask :)


FLAME IONIZATION PRINCIPLE

Heat in the flame causes the molecules in and around the flame envelope to collide with one
another. The force of the collision frees some of the outer electrons of the atoms forming the
molecules. This creates free electrons and positive ions, allowing a very small current to be
conducted through the flame. The whole process is called Flame Ionization.
Within the flame there is very low conductivity and resistance can vary from 100,000 to
100,000,000 ohms. Current conducted through the flame (flame current) is generally in the
range of 2-4 micro amps. If two electrodes were placed in a flame as in
Figure 14, and a voltage applied, a current could be conducted between the two rods
(Flame Rods). Naturally the positively charged ions would flow to the negatively charged rod.
In order to use this process to determine presence of flame and to prevent the potential hazard
of a high resistance short to ground (effectively simulating flame signal), the flame
current is rectified. Generally referred to as a Flame Rectification System, this is achieved
by placing a grounding electrode in the flamewhich is several times (generally 4 times) larger
than the flame rod or electrode. An AC supply voltage is applied across the electrodes. In the
first half of the AC cycle, the flame rod is positive and the ground rod is negative. The positively
charged ions will flow to the negatively charged grounding area.
The large grounding area increases the capacity to hold electrons. This results in a relative
high flame current flowing through the flame during the first half cycle.
During the second half cycle, the reverse process will take place. This results is a much
smaller flame current, rectifying the AC current through the flame. The only type of current
accepted by the system is the rectified flame current. Any high resistance type short circuit will result in an AC type flame current which is rejected by the FSG control. The large grounding
electrode generally forms part of the burner fuel nozzle .

Flame rods are small diameter metal rods supported by an insulator. The tip-end of the
rod can project into the flame. They typically are made of Kanthol, a high temperature alloy
capable of operating in temperatures of up to 2400 F (1300C). Other materials with higher -
temperature ratings, such as Globar (a ceramic material) are also available.
Applications for flame rod, rectification type flame detection in multi-burner applications are
generally found in the supervision of gas fired igniter flames.
Requirements for successful applications include:
• Gas burners only (premixed where possible).
• Adequate flame rod to grounding area proportioning
(4 to 1 minimum).
• Stable flame (no movement from flame rod).
• Proper placement of flame rod in flame
(short as possible, yet adequate contact).
• Proper rectifying flame current and associated
circuitry
 
Well what about those two Black Wires?

Your tips are appreciated. I have resorted to pulling the fuse as I delay in this repair. That stops the reigniter from sparking but the fridge keeps on cooling (flame keeps burning) even when the light is not working inside the cooler! (Funny isn't it that your mind say's "Fridge Warm" when the lamp is not on inside?)

The Flame Ionization Theory seems very plausible! I will try to find a new reignighter module here in Turkey tomorrow and give it a try a.s.a.p. I am still not convinced that those two black wires on the thermocouple of the thermostat don't have a part in this? Does anyone know what they do?
 
in commercial gas circuits two wires coming from a thermocouple are used as part of a safety shutdown circuit if you unplug it does the gas shut off?

yes it's to cut the thermocouple voltage to the gas valve and shut the gas off it goes to the multi purpose control switch, the wiring diagram is at the end of the manual, I found a copy online here

http://www.swift-owners-club.com/support/oem-handbooks/dometic/RM6270-6401.pdf
 
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outtolunch said:
yes it's to cut the thermocouple voltage to the gas valve and shut the gas off it goes to the multi purpose control switch,
Click to expand...
Absolutely correct, there was a post either on this forum or one of the lesser ones :) where somebody had stripped that down and cleaned it because his gas supply kept cutting off, if I remember correctly the module I bought was about £25 so it will be a cheap fix
 
DOMETIC - Just In...

Just got this Email from Dometic.... I will follow suit and reply here with results A.S.A.P.Good morning,

Many thanks for your email,

They symptoms you are describing could indicate a number of faults.

I would recommend you check the following,

Check the cables from the ignitor to the switch aren't loose or damaged.

Check that the fridge and the ignitor have a good earth.

If both of these are ok.

Turn the selector switch on and off a number of times it is possible the contacts inside the switch are dirty switching on and off may clean the contacts temporarily to give you an indication to where the fault lies.

I have attached a wiring diagram for your information.


Please be aware that only Gas qualified engineers should work on the gas aspect of any product.
 
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