QuestionDarren, thanks for the reply. Do you have any explanation as to why the reigniter only sparks once as opposed to the 45 seconds it is supposed to try? I'll try the direct 12v battery - that's how I discovered the bad positive cable from the battery - that will eliminate the convertor and any a/c ripple. If I decide to replace the circuit board do you recommend I use one of the Dinosaur boards I've read about?
Thanks,
Bob
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Followup To
Question -
I have a Dometic 3807 AES 3-way refrig. I recently replaced a bad power cable from the refrig to the battery and got the unit working again. However, its working erratically, sometimes not sensing there is 120v available, and mostly giving a check light on gas. It will start on gas but I've noticed it will only spark one time, which is abnormal. The thermocouple seems to work fine, putting out about 24 mv when heated and quickly drops to near 0 when the flame goes out. Once the flame goes out the reigniter does not spark again.
Does this sound like a reigniter problem, ground problem or main circuit board problem to you? I have Dometic's service note which hasn't helped too much.
Thanks for your thoughts.
Bob
Answer -
Hi Bob,
It sounds like most likely a circuit board problem if you have a good 12 volt supply to the frig. The two most common problems I have found that are hard to track down is too much A/C ripple in the DC circuit from the converter and plugging into an outlet with reverse polarity. These can both cause extreme erratic behavior. You might try hooking the frig up direct to a 12 volt battery and see if that helps any. I am enclosing the service note I have on this unit at the end in case it is different from what you have. Good luck.
Darren
INTRODUCTION
The purpose of this bulletin is to aid the servicer in proper diagnosis and repair of AMES/AES refrigerators. This bulletin will provide the servicer with information to find the hidden variables that can cause an erratic check light.
DC POWER SUPPLY
Cleandirect current (DC) power is mandatory for high tech circuits to operate as designed. The sources for DC power are a battery and converter. A battery will provide recharging of the battery by the converter or the alternator.
The converter and alternator produce DC power by a series of diodes that rectify alternating current to DC. A battery or capacitors can be used to clean up the AC ripple that is present after AC voltage has been rectified.
AC ripple can be measured by a voltmeter set on the AC scale at the main terminal block connections. Six volts AC or less is acceptable.See Fig 1
A brief interruption of the DC power supply while refrigerator is operating on gas can cause a check light; for example: Turning the refrigerator OFF-ON while operating in the gas mode can cause a check light. The switching of relays from converter power to battery power when unplugging from shore power or shutting down of the generator could interrupt DC power long enough to cause a check light.
The thermocouple produces 25-30 MVDC when operating. When DC power is interrupted and restored, the thermocouple may not have sufficient time to cool. If the power module sees above 6 MVDC, when power is restored the power module will assume a problem in the gas mode and immediately turn on the check light.
2. GAS SUPPLY
The refrigerator requires 11 inches water column with half of all the BTU's of the RV turned on ( half of all appliances turned on ). With all the appliances off, the pressure to the refrigerator should not exceed 12 inches water column. The gas pressure for the refrigerator is taken at the test pore after the solenoid with the refrigerator operating
3. GROUNDS
A. A quick easy way to test for ground problems can be done with a millivolt meter.
1. Connect a millivolt meter to J3 of power module and the negative (-) connection of the main terminal block.
2. Pull one of the wires off the gas solenoid valve. The millivolt reading should be one or less.
3. Put the wire back on the gas solenoid valve and with the reigniter sparking, the millivolt meter shows more than six a ground problem exist. Proceed to section B.
4. The millivolt meter should register between 25-30 millivolts with the gas flame burning.
5. Shut the manual gas cock valve off and watch the millivolt reading as it drops. Note the millivolt reading when the reigniter starts sparking (7-13MV).
B. Relocate Gas Solenoid Ground
1. Clean terminal J3 and J10 on power module.
2. Remove wire from J10 and tighten the terminal with pliers. Do both ends of the wire.
3. Remove white wire from gas solenoid valve and connect to the ground strip.
4. Connect a piece of wire (16 gauge minimum with a ring terminal on one end and 1/4" spade connector on the other end) between the gas solenoid and the ground terminal strip. Place the ring terminal under the screw on ground strip.
5. Reverify section 3A3.
4.COMPONENTS
A. The Thermocouple is a component extending above the burner assembly so the tip is in the path of the flame. During normal gas operation, the thermocouple should produce 25 to 30 millivolts when connected to the lower circuit board. Any reading below 18 millivolts could cause erratic gas operation. NOTE: A reading of 18 or less could be caused by low gas pressure or improper thermocouple location. The thermocouple should be centerd over the burner and extended over 3 slots.
B. The burner is a horizontal slotted metal tube located below the flue tube of the cooling unit. The burner should be cleaned periodically ( at least once a year). To clean the burner remove from the refrigerator and check for any foreign residue ( rust, spider webs, etc.) that could cause a defection of the gas flow or flame. Soak the burner in an alcohol based solvent and allow to air dry. Reinstall in refrigerator and leak check all gas connections with an approved leak check solution.
C. The Rrigniter is an electronic device that produces high voltage to create a spark at the burner only on gas mode. Verify proper Dc power is at the positive (+) and ground (-) terminals. The reading should be within one volt of the voltage at the main terminal block during the trial for ignition.
D. Electrode
First do a visual check for cracks or breaks on the ceramic insulator. Verify the mounting bracket is attached properly to the electrode. If either of the above is found, replace the electrode. The spark gap must be set at three sixteenths (3/16") of an inch and tip of electrode above the slots in the burner. If reigniter and high voltage cable are good and there is no spark at the electrode, replace the electrode.
E. The Solenoid Valve receives DC power when the AMES/AES control selects LP gas operation. The solenoid coil opens an internal valve seat and allows gas to follow to the main orifice. Check the solenoid valve with a properly calibrated ohm meter. Remove one of the connectors from the solenoid and measure the resistance across the terminals. The proper calibrated ohm meter. Remove one of the connectors from the solenoid and measure the resistance across the terminals. The proper reading would be 44-53 ohms. Hook a manometer to the test port. With Dc power supplied to the solenoid terminals, a gas pressure reading of 11-12 inches of water column should be present. If no pressure or low pressure is present at the test port, the gas solenoid is defective and should be replaced. NOTE: Verify the LP gas system pressure before replacing a valve with low pressure.
F. The Power Module monitors the DC, Ac and gas in conjunction with the setting of the display panel.
Check the fuses under the cover on the power module for continuity. Replace with same size if bad. Inspect for loose relay and plug 3 on the board.
When the refrigerator requires additional cooling the power module will send DC voltage to be the solenoid and reigniter. The trial for ignition will last for 45 seconds and at the same end of this period the check light will come on. NOTE: When the thermocouple output is between 7-13 millivolts DC, the DC voltage to the reigniter will be turned off. If the flame is extinguished the power module will not supply DC power to the reigniter until the millivolts DC drop to 7-13 MVDC. It may take 10-15 seconds for the thermocouple to cool. The PAL Tester will allow for proper testing of the integrity of the upper and lower circuit cards. The PAL Tester is available from your Dometic parts distributor.
G. Control Board
1. With the main ON/OFF switch on the control panel in the OFF position: Check for DC voltage at plug 1 terminal 4 of lower circuit board.
If no voltage check the fuse condition on lower circuit board. Replace if blown. Check for DC between J4 and J10 on the lower circuit board. If fuse is good and there is DC voltage at J4 remove and replace lower circuit board.
2. With main ON/OFF switch on the control panel in ON position:Check for DC voltage at plug 1 terminal 1 of the power module. If no voltage is present then the switch is faulty and the control panel should be replaced. If DC voltage is present at P1 terminal 1 check for DC voltage on P1 terminal 3 on the power module. If there is NO DC power present the power module is faulty and should be replaced.
AnswerHi again Bob,
Does it only spark once if the gas is off and it doesn't light? I have had several Dometic frig's that would only spark once and the flame would light and they ran fine, but if you turned the gas off they would keep trying to ignite, or if you blew the fire out they would light right back up. We have been using the Dinosaur boards for a year or so and haven't had any problems with them and I believe they come with a three year warranty so I would have to say yes to that question. Good luck with the repair and let me know how it goes.
Darren
