SURE MARINE SERVICE INC.
This oven troubleshooting guide was written specifically for
Seaward / Princess / Hillerange stoves manufactured prior to September 2007
It is applicable to many other brands of RV & marine stoves including many Magic Chef, Wedgewood, Kenyon, & early Gas Systems ovens.
Starting in mid 2007 Seaward redesigned their oven controls, eliminating the mercury control valve
and making this troubleshooting guide not applicable to models built after mid 2007.
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Only properly trained personel should attempt gas applance repair.
Improper repair can lead to property damage, injury or death.
Feel free to contact Sure Marine if you require assistance or parts at (206) 784-9903.
The basic oven components are the oven thermostat, the mercury control valve, the pilot assembly and the main oven burner
Later versions are also equipped with an oven thermocouple & safety valve.
All Seaward / Princess / Hillerange stoves built after 1993 should have an oven thermocouple & safety valve.
Stoves built between 1984 & 1993 might have an oven thermocouple & safety valve.
If simply turning the oven control knob allows gas to exit the pilot assembly there would be no 'oven thermocouple'.
Most stoves built prior to 1984 would operate this way.
If you do have an oven thermocouple, you would need to depress a button in order to light the pilot.
INFORMATION ABOUT THE SAFETY VALVE AND PILOT ASSEMBLY
If your stove is equipped with an 'oven thermocouple', you should be able to see a threaded probe mounted directly above the pilot flame.(see photo above)
You would also have a push button on the front of your stove in order to light the pilot.
If you are having trouble getting the pilot to stay lit after you release the push button, verify that the tip of the probe is covered with flame in the 'low pilot mode'.
If the probe is in the flame, but the pilot flame goes out as soon as you release the button, there are a few possible causes.
The thermocouple could be defective. ( a thermocouple is an electrical device that generates a small voltage when heated. )
The electromagnet inside the safety valve could be defective. ( The safety valve has the push button you need to depress when lighting the pilot ).
You could have a bad connection between the thermocouple & safety valve ( loosens with a 5/16" wrench, wire brush end & reassemble. Don't over tighten ) Generally you need to hold the button for about 10 seconds after the pilot is lit, then release the button and the pilot stays on.
The 'safety valve' and 'oven thermocouple' only effect the pilot staying lit,
If you can get your pilot light to stay lit, these parts are probably not defective.
INFORMATION ABOUT THE THERMOSTAT
The 'oven thermostat' monitors the oven temperature using a sensing probe usually located in the top rear of the oven.
It compares the oven temperature to the temperature you have selected with the oven dial.
It modulates the pilot flame height up to 'high pilot' when there is need for more heat, & down to 'low pilot' when the oven is at temperature.
That is basically all it does, it modulates the pilot flame up & down.
In the "oven off" position it also blocks gas going to the 'mercury control valve'.
During normal operation, the only component physically blocking gas to the main burner is the 'mercury control valve'
INFORMATION ABOUT THE MERCURY CONTROL VALVE
The 'mercury control valve' monitors the pilot height using a small probe mounted in the end of the pilot assembly.
When it senses a large pilot flame ( because oven thermostat has sensed a need for more heat ), the 'mercury control valve' opens and allows gas to flow to the 'main oven burner'.
The 'mercury control valve' itself is normally located directly behind the thermostat, but in early stoves it can be mounted in the side wall of the oven.
It is often replaced by the customers due to a misdiagnoses of an oven problem.
The 'mercury control valve' acts as a safety feature, if there is no pilot flame present in the oven, it prevents a large amount of gas from entering the oven cavity.
If you can ever get the oven burner to come on, the mercury control valve is probably not defective
DIAGNOSING A PROBLEM
If you can get the pilot to light, and you can get the main burner to come on, but periodically everything, including the pilot light goes out, you probably have dirt in the pilot orifice.
The pilot orifice is located at the inlet to the pilot assembly behind the 3/16" compression nut ( requires 7/16" wrench ).
Many oven problems can be traced to issues with the pilot assembly
This problem could also be caused by a bent pilot assembly, low gas pressure or a sticking propane regulator.
If running a top burner while operating the oven eliminates the problem it would point towards a sticking propane regulator.
If your stove is equipped with an 'oven thermocouple', verify that the thermocouple's probe is directly over the flame in 'low pilot' mode.
If the pilot does stay lit, but the main burner does not light you need to verify proper operation of the oven thermostat.
Verify you have two distinct pilot flame heights 'low pilot height' when the oven is up to temperature ( or in pilot only setting ), and 'high pilot height' when the oven is colder than thermostat setting. ( ie. oven cold & control knob set to 500F ).
Try lighting the pilot, and turning the control knob up and down, You should see the two different pilot flame heights.
If the flame goes out when transitioning between the two flame heights, there is probably dirt in the pilot orifice or you have a bent pilot assembly.
These are common problems.
The 'high pilot height' is limited by a pilot orifice inside the pilot assembly.
The 'low pilot height' is limited by a tiny orifice located inside the oven thermostat.
If you only have gas flow at high pilot, but zero gas flow at low pilot, this internal orifice is probably clogged.
If you only have a 'low pilot height' at all temperature settings, then you have a defective thermostat ( or severely clogged pilot orifice ).
Remember, all the thermostat does is monitor oven temperature & modulate the pilot flame height.
If you have two pilot flame heights, but the main burner doesn't come on, it is often dirt in the pilot orifice.
Try turning the thermostat up until you achieve 'high pilot height', then take a lighter or small torch and apply additional heat to the probe located in the end of the pilot assembly.
This is the probe connected to the 'mercury control valve'.
If the burner does come on, then the pilot flame just wasn't getting the probe quite hot enough.
This can take some time, so a plastic ended gas match or Bic lighter are not the ideal tools for this test
Most lighters are not designed to run continuously for a minute or two.
Again, this is probably dirt in the pilot orifice, but could also be caused by a bent pilot assembly, mis-located sensing probe or low gas pressure.
If you have the thermostat turned up, and the pilot size is big, and you apply additional heat to the probe but the main burner still won't light, you probably have a defective mercury control valve.
The burner should come on before the probe glows red hot
In theory, the oven burner jet could be clogged, but this would be unusual.
In a Seaward / Princess / Hillerange, if the mercury control valve is located on top of the stove it is part #72532.
If the mercury control valve is located in the side wall of the oven, it is probably part # 70402.
There are several variation besides these common two.
The 72532 & 70402 are both factory discontinued items, there are a limited number of remanufactured units available,
Some of the remanufactured units require modification of the supply lines. Call for availability.
If you purchase a replacement, please send your core back for credit in a timely manner.
PILOT ORIFICE REPLACEMENT
A new pilot orifice is part #70392 for LPG. #70393 for CNG
You can possibly clean / blow through the pilot orifice and reinstall it.
The hole is tiny, don't stick a needle in it or you will probably ruin it.
To remove the pilot orifice, start by removing the 3/16" propane line using a 7/16" wrench.
The orifice may simply fall out, or you may need to pry it out using a nail or small screwdriver.
It's shaped like a tiny thimble.
Insert the tool through an air hole located just beyond the threads past where the propane line was removed.
Use caution as the orifice is easily damaged.
If your oven does not have automatic spark ignition you can turn on the oven control briefly ( and depress the safety valve button if applicable ) to blow out the pilot supply line in case there is more dirt inside.
OVEN THERMOSTAT REPLACEMENT
If you need to replace the oven thermostat, many styles have been discontinued.
There is a replacement thermostat kit available, but it may require several modifications
There are many different configurations, more than I can describe here.
If you are not sure what parts you need, you can email us photos.
The most common thermostat is the #70400.
The #70400 ( CNG version is #70401 ) can be identified by the "triangularish" shaped copper plate attached to the rear of the thermostat body.
As with all seaward thermostats, incoming gas enters through the bottom of the thermostat.
There are two gas lines leaving the thermostat, a 3/16" supplying gas to the pilot light & a 1/4" line supplying gas to the main burner via the mercury control valve.
the 70400/70401 is only available remanufactured & currently the demand greatly exceeds the supply.
We are attempting to collect more cores to rebuild, so it is important that people return their defective 70400 thermostats in a timely manner.
The Seaward thermostat is unusual because it shuts off the pilot in the off position( as required by the USCG / ABYC. )
Residential standing pilot style oven thermostats are designed so that the pilot stays lit all the time.
If your mercury control valve is located in the oven wall, there is a generic thermostat kit that fits with little modification.
The generic kit is a factory Seaward item & will fit all stoves with some modification to the gas lines.
The kit is part #74498-KIT
REQUIRED MODIFICATIONS TO CONVERT FROM A 70400 TO THE 74498-KIT IF YOUR MERCURY CONTROL VALVE IS IN THE OVEN
Note that the 74498-KIT will not work with Natural Gas (CNG) stoves. If you need a Natural Gas thermostat, contact us.
The original thermostat mounting saddle will need to be replaced; It requires thread sealer to install.
Teflon tape is NOT recommended, use a propane approved paste. We have it if you don't.
The end fitting on the 1/4" tube will need to be converted from compression to the R53634.
This normally requires carefully filing off the old ferrule without damaging the tubing,
If your tubing is long enough you can simply cut the ferrule off.
In the stove shown below, the gas line is plenty long enough to just shorten & rebend.
The fitting on the 3/16" line does not need to be replaced unless damaged.
Both lines will need to be bent upwards slightly, as the gas connections are tipped slightly downward.
Be extremely careful that you do not cross-thread the gas fittings into the thermostat.
The old 70400 thermostat temperature markings on your stove will not match the new thermostat.
A new knob & decal are provided.
The temperature probe on the new thermostat will need to be routed back into the oven.
This can be a little tricky, but you do not need to disassemble your stove to get the probe back into the oven.
When you remove the old probe, pay close attention as to how it is routed as you remove it.
If the stove is propane and your current oven supply lines are made of aluminum, they should be upgraded to copper.
Natural Gas (CNG) is not compatible with copper, closely inspect the aluminum lines for corrosion or pitting.
Old aluminum supply lines are bad news. Most stoves have stainless lines & are fine.
This propane system is only pressurized to about 1/2 PSI, you do not need to overtighten the fittings.
Flare nut wrenches are recommended.
If your stove already has a #74498 installed the thermostat is also available separately
REQUIRED MODIFICATIONS TO CONVERT FROM A 70400 TO THE 74498-KIT IF YOUR MERCURY CONTROL VALVE IS ON TOP OF THE OVEN
Note that the 74498-KIT will not work with Natural Gas (CNG) stoves. If you need a Natural Gas thermostat, contact us.
If your mercury control valve is located on top of your stove, the conversion kit will be slightly different.
The conversion will require replacing the existing pre-bent stainless steel gas supply line.
If your existing gas line is "Z" shaped, you will need to order part#80424 in addition to the #74498-kit
If your existing line is "U" or "G" shaped, you will need to order part #80424-G in addition to the #74498-kit
The original thermostat mounting saddle will need to be replaced; It requires thread sealer to install.
Teflon tape is NOT recommended, use a propane approved paste. We have it if you don't.
The old 70400 thermostat temperature markings on your stove will not match the new thermostat.
A new knob & decal are provided.
The temperature probe on the new thermostat will need to be routed back into the oven.
This can be a little tricky, but you do not need to disassemble your stove to get the probe back into the oven.
When you remove the old probe, pay close attention as to how it is routed as you remove it.
You only need the additional gas lines if you are replacing a defective 70400 with the new style 74498 thermostat and your mercury control valve is located on top of the oven.
MERCURY CONTROL VALVE REPLACEMENT
If your mercury control valve is located in the oven, make sure that we are aware if the replacement is for LPG or CNG.
If your mercury control valve is mounted on top of the oven, there is a designated runway for the sensing probe to route through.
In the sidewall of the oven is a small tube to push the replacement probe through.
The tube is perfectly straight, so you will need to reach into the sidewall of your oven & snag the new probe with your finger.
Closely watch how the old probe is routed as you remove it.
Make sure to tuck any excess length of tubing up so that it can't become snagged & damaged.
Do not locate the excess sensing probe's tubing where the main burner's flame can hit it.
REMEMBER TO LEAK CHECK ALL CONNECTIONS BEFORE USING THE STOVE.
TO BE SAFE & ABYC COMPLIANT, YOUR PROPANE SYSTEM SHOULD HAVE A 300PSI PRESSURE GAUGE INSTALLED BETWEEN YOUR PROPANE TANK & REGULATOR.
THIS GAUGE IS PROVIDED SOLELY TO LEAK CHECK YOUR PROPANE SYSTEM.
IF YOU DO NOT HAVE A PRESSURE GAUGE INSTALLED, WE CAN PROVIDE YOU WITH THE NECESSARY PARTS TO INSTALL ONE.
TO LEAK CHECK YOUR SYSTEM, FIRST MAKE SURE THE MANUAL VALVE ON YOUR PROPANE TANK IS CLOSED.
IF SYSTEM IS EQUIPPED WITH AN ELECTRIC GAS VALVE, TURN IT ON.
OPEN THE MANUAL VALVE ON YOUR FUEL TANK BRIEFLY, THIS SHOULD PRESSURIZE THE PROPANE SYSTEM UP TO THE BOTTOM OF THE THERMOSTAT
IMMEDIATELY, CLOSE THE MANUAL VALVE ON YOUR PROPANE TANK AGAIN & LOOK AT THE PRESSURE GAUGE.
FOR A PROPANE SYSTEM TO BE CONSIDERED LEAK FREE, IT MUST HOLD PRESSURE WITH ZERO PRESSURE DROP FOR AT LEAST 3 MINUTES.
IT SHOULD RETAIN SOME PRESSURE AFTER ONE HOUR.
CONNECTIONS AFTER THE THERMOSTAT ARE ONLY PRESSURIZED WITH THE OVEN THERMOSTAT TURNED ON.
YOU WILL NEED TO LEAK CHECK THESE CONNECTIONS VERY CAREFULLY.
YOU CAN USE A SOAPY WATER SOLUTION & CHECK FOR BUBBLES, CLEAN UP THE EXCESS WHEN DONE.
DO NOT USE ANYTHING WITH AMMONIA, IT WILL ATTACK THE BRASS FITTINGS, USE DISH SOAP OR SIMILAR.
COMMERCIAL LEAK DETECTION FLUIDS ARE BEST BECAUSE THEY DO NOT LEAVE A CORROSIVE RESIDUE. WE HAVE IT IN STOCK.
REMEMBER THAT PROPANE IS DANGEROUS, IF YOU ARE NOT PROPERLY SKILLED TO PERFORM THIS TYPE OF WORK, HIRE A PROFESSIONAL.
IT WILL BE MONEY WELL SPENT.
If you can not positively identify your stove in the pictures on this page take a few photos and email them to us so we can be certain you get the right parts the first time.
Sure Marine Service Inc.
5320 28th Avenue NW, Seattle, Washington 98107
800-562-7797, 206-784-9903, Fax: 206-784-0506