Atwood Model G6A-8E water heater fails

[robrv3]

I have an Atwood Model G6A-8E water heater that won't run without stopping and the red light going on. What I need to know are the operational parameters of the MPD 93307 control module.
1) My measurement show the the controller only turns on gas for .8 seconds or 800 milliseconds before returning an error and shutting down the water heater.
2) I can turn off and turn on the water heater 30 or more times and it will successfully ignite and run every time suggesting ignition is okay however if blow the gas out of the air shutter and burner tub with an air hose the fails to lite and operate 2 out of thee times. I think this suggest that perhaps 800 milliseconds is not sufficient time for the gas to propagate down the burner time and have ignition.

I contacted Atwood and they are completely useless in providing information

[robrv3]

problem resolved I cleaned and gapped the igniter the gap was about 3/32 set the gap to 1/8, The module now waits 7 seconds before it stops and indicates an error to test this I had to turn off the gas then turn on the heater. I not sure why doing this the module gives more time for ignition and why it fired up 100% of the time when I turned the water heater power on and off but wouldn't run overnight before I cleaned and gapped the igniter. Top signal is error light bottom signal is gas solenoid power

[phays]

rborv3, I appreciate seeing real data, something we very seldom see on this forum. Once you solve the problem, use your scope again and you will have a base line for your ignition sequence for your water heater.

Try this Atwood service manual for help.

[dougrainer]

You HAVE to be an engineer. ONLY they have the time to waste on using equipment that is useless for this problem. Listen to Old Biscuit. You have a BAD Ignition module. The system is EXTREMELY simple. It gets 12 volts plus and then sends the 12 volt signal to the Gas valve for 8 seconds and has the Piezo tower spark for 8 seconds. IF the 12 volts to the gas valve lasts only for 800 milliseconds, the module is defective. BTW, it takes NO tools to figure this out other that a voltmeter or a 12 volt test light. I do it with NO tools, just listen to the Gas valve click or put my hand on it to feel if the valve clicks off. Have you bypassed the ECO tstat? The power to the gas valve goes thru it. Doug

[Old-Biscuit]

robrv3 wrote:
Measured with an oscilloscope. I have a bmp image wish I could post it. It doesn't seem .8 seconds or 800 milliseconds is enough time

It ISN'T.......

Like I posted. 12V DC s/b on gas valve solenoids for 6-8 seconds while spark electrode is firing

6-8 Seconds

[robrv3]

Measured with an oscilloscope. I have a bmp image wish I could post it. It doesn't seem .8 seconds or 800 milliseconds is enough time. I put the oscilloscope wave form up as my profile pic

[Old-Biscuit]

When you turn the propane switch ON the spark electrode should start firing and 12V DC should be sent to gas solenoids for 6-8 SECONDS allowing gas valve to open, propane to flow, flame to ignite and then PROVE it has lit.

How are you measuring the time .....800 milliseconds :H

Brown wire......12V DC from on/off switch to module (thru thermal fuse/t-stat)
Red wire,,,,,,,,12V DC from module to gas valve (thru ECO)
Blue wire-------12V DC from module to 'Fault' Light (no flame proven fault OR ECO open)
Green wire......Ground


ECO (high temp t-stat. IF it opens (OR fails to allow DC to gas valve) fault light
Terminals/spade connectors on ECO dirty/corroded----resistance impedes DC

Spark electrode...provides high voltage spark BUT also used to transmit signal generated by main flame used to prove it lit (flame rectification ---milliamp signal)
Spark electrode has to be 'engulfed' in flame....spark gap s/b 1/8" - 3/16"
Ceramic cracked....signal tracks to ground

Module.......has to have good clean ground


800 milliseconds :H

If so..........module failing