Atwood 10 gal DSI lights then goes out

[mrgrayaz]

Last appliance to go on our Alfa....'ol trusty the Atwood 10 gallon DSI water heater. Worked great until last week, while I fixed both the fridge and furnace this winter...For awhile there it was the ONLY propane thing working besides the range...

Unit keeps giving me the red finger, er I mean light when turned to propane.

• Gas pressure is good measured at the stove. (I got a manometer after the furnace fiasco) 11.x" WC with furnace and fridge on
• I have cleaned the updraft pipes with a vacuum
• Electrode alignment to burner tube is good
• I can see spark. I also shocked myself with the electrode off the board. Ouch! We have spark.
• I can hear the gas valve turning on and off and smell gas. *clunk on clunk off*
• I have sanded/wiped down all the spade connectors and connected/disconnected multiple times. Connections *look* good.
• I sanded the ground and reattached.
• Flame, when it lights is mostly blue around the distributor/blocker at the end of the burner, with some yellow. Flame is steady.

The only thing a little off is the airflow induction on the burner- Per the Atwood manual it says I should have 1/4 of air holes exposed on the burner - I have more like 3/4. The burner tube is rusted together from the expansion valve dripping and I can't adjust this. Either way, this hasn't changed in a long time judging by the rust.

What it appears to be doing is the following:

• Gas valve on *clunk*
• *Spark spark spark spark spark* on and visible in the dark
• Flame lights *whomp*
• Gas valve off. *clunk*
• wait 2 secs and repeat
  

The entire evolution takes about 2 seconds. maybe.

It will do this 2-3 times either resulting in lockout or it will stay lit on the third
try. When lit, I am not getting that loud whooshing flame like I am used too - it is essentially silent. I used to be able to hear the unit running from within the Coach (not a bad sound, just you could hear it). Unit does get the water up to the usual scalding temp once it has lit.

I'm guessing either electrode - which looks to have been replaced already...or the board.

Thoughts?

[mrgrayaz]

To clarify, being that I have spark and I have gas - I am leaning towards a flame sensing issue. Being that electrode is functional and looks fairly new.....new board is where I am headed. Our fridge had the same issue when it needed a new board, fully functional on 120v and very intermittent propane functionality...

Unit uses a 93851, or a UIB 64....probably go UIB 64. Guy @ Dinosaur has been good to me.

Am I crazy? Anything I miss?

[Old-Biscuit]

Spark electrode proves the high voltage spark used to ignite main flame
BUT is also the means by which the 'flame proven' signal gets back to circuit board.
Circuit board only sends DC Voltage to gas valve solenoids for 6-8 seconds during 'trail for ignition'
No return signal.....DC is dropped from gas valve circuit

Flame Rectification......ions/burning burning fuel etc
A miliamp signal is generated by main flame. It goes back to circuit board via the spark electrode and high tension wire.
Being a miliamp signal it doesn't take much resistance to stop it OR for it to go to ground

Spark electrode wire.....must be clean/tight on terminal
Spark electrode ceramic can NOT have cracks.....signal with track to ground and it has to be clean (wipe down with a rag sprayed with silicone)
Spark electrode MUST be 'engulfed' in main flame for signal


AS for air shutter.....
1/4 OPEN is standard starting point..
Typically provides sufficient air for proper air/fuel ratio.......Strong BLUE slightly loud flame
Unable to adjust due to rust....time for a new burner tube

AND maintain a 'air pocket' in top of WH Tank so T&P Relief Valve doesn't weep
Not only does the drip drip drip rust out parts it can also corroded spade connectors on t-stat/ECO and gas valve solenoid

Dino Boards are GOOD----IF problem is with circuit board (not common)
Get the protective cover .......Dino board is exposed

[70ChevelleSS]

Originally Posted by Old-Biscuit

...Flame Rectification......ions/burning burning fuel etc
A miliamp signal is generated by main flame. It goes back to circuit board via the spark electrode and high tension wire.
Being a miliamp signal it doesn't take much resistance to stop it OR for it to go to ground...

Had the same problem on ours. The wire inside the ceramic was corroded through. Higher voltage to ignite could get through. Milliamp return signal couldn't.

[mrgrayaz]

I've ordered a new igniter and a new burner tube - total was $35 shipped, so not expensive. I'll update the thread when I get them in....

[mrgrayaz]

I received my new burner and igniter in the mail yesterday.

Installed the igniter first and that does seem to have resolved my issue. The old igniter externally looks just fine....

We are dry camping for the next week so I will be giving the propane feature a workout and will update again.

[mrgrayaz]

We have been dry camping now for over a month - I'm going to call this good. It doesn't always light on the first try, but it's darn close...

[mrgrayaz]

And its back up to its tricks ...different symptoms now.

The furnace will light every time...with the door open. With the door closed, it tries 3 times and then fails. I can immediately reset, open the door, and it lights.

I never did replace the burner tube. Sounds awful like gas to air mixture doesn't it?

The existing rusted open burner tube is fully open.

Any ideas?

[Old-Biscuit]

As the gas flows thru orifice the air is pulled into burner tube and mixes with the gas until it hits the spreader plate where ignition occurs.

The air/gas mixture is critical for proper combustion

Air/gas must flow straight down burner tube w/o bouncing around

Your rusted up burner tube is culprit.

Install that new shiny burner tube........align it so that it is a straight shot from gas valve to combustion chamber and reset spark electrode.

[mrgrayaz]

Originally Posted by Old-Biscuit

As the gas flows thru orifice the air is pulled into burner tube and mixes with the gas until it hits the spreader plate where ignition occurs.

The air/gas mixture is critical for proper combustion

Air/gas must flow straight down burner tube w/o bouncing around

Your rusted up burner tube is culprit.

Install that new shiny burner tube........align it so that it is a straight shot from gas valve to combustion chamber and reset spark electrode.

I can't get this sucker to fire door closed.

Got the new burner installed and aligned with the gas tube.... Had to bend the bracket to make that happen. Have a nice blue flame with a smidge of yellow, no sputtering with the tube 1/3 open - runs really nicely door open or closed. Good flame, good heat.


Pics of flames are hard, but it's a nice clean burn.

Won't light door closed. Arrrgh!!!!

[Old-Biscuit]

Two common issues......intermittent ignition (actually there are 4 but these two are more likely your problem)

Flame Spreader
Needs to be 'parallel' with end of burner tube........if not gas/air mixture can be directed away from ignition spark

Spark electrode/ground rod gap
1/8"
And both spark electrode/ground rod need to be engulfed in main flame when lit

Open air shutter until flame is BLUE/BLUE and LOUD then slightly close ----S/B blue w/just a tinge of yellow and slight roar


Did you clean main gas orifice?
Proper gas flow thru orifice is what 'pulls' air in thru air shutter.

Remove from gas valve, soak in alcohol then lightly blow it dry (just use your breath.....high pressure from air compressor can damage orifice and never stick anything thru it)

[tmw188]

Is the door pushing on the igniter wire? Seems odd that it won't ignite, I could see maybe not staying lit for long with door shut, but just igniting seems very odd.

[mrgrayaz]

Ok tweaked the igniter to 1/8" - was probably more like 3/16" - new igniter so I left the spacing it came with. No change in behavior.

Checked the flame spreader - I used the new one that came with the tube and bit looks good. I tweaked it a bit - no change in behavior.

I have not soaked the gas valve - I may try that next.

I had an interesting idea to pull the igniter back towards the flame spreader and that seems to be working. Removed igniter from its forward screw hole, and just screwed it onto the back of the mount with a washer.
Its pulled the igniter about 3/4" back so it's right next to the flame spreader, not an inch down the tube and it lights ever time. Very interesting. Weak spark?

[mrgrayaz]

WATER HEATER LOCK OUT - GAS AND SPARK PRESENT
Gas pressure incorrect ------------------------------------------Set inlet pressure at a minimum 11˝ W.C. with two or more gas
appliances running
Low voltage--------------------------------------------------------Correct power supply - 10.5 VDC minimum
Poor electrical ground--------------------------------------------Secure electrical ground
Electrodes out of flame pattern --------------------------------Re-adjust electrodes
Electrodes sparking to screw fastening burner to flue tube Adjust electrodes away from screw
Dirty electrodes --------------------------------------------------Clean electrodes
Partial obstruction in main burner------------------------------Clean main burner
Partially obstructed main burner orifice------------------------Clean main burner orifice or replace
Improper air adjustment ----------------------------------------Adjust main burner air shutter approximately 1/4 open
Flame spreader on main burner out of adjustment ----------Adjust flame spreader so that it is square to the end burner tube out
of alignment of the main burner
Manifold not aligned with main burner ------------------------Re-align solenoid valve with main burner
Partially opening solenoid valve --------------------------------Replace solenoid valve
Defective circuit board--------------------------------------------Replace circuit board