AtWood HE0601 - Gas lights, but it doesn't recognize

[mnopneal]

Trying to help a friend with an Atwood HE0601. RV service people have abandoned them.

It works fine on AC power. On gas, it will fire the ignitor, light the burner, then continue to fire the ignitor, through the 20 seconds, 10 seconds, 6 seconds, and then apparently it decides there is no flame and cuts off the gas.

I have downloaded the skimpy Atwood service manual on this. Thus far I've not figured out HOW it is supposed to detect a flame.

I see a Thermal Cutoff Switch (#50 on the diagram) located up on the stack above the burner. This is reading 1.4 ohms at the switch when the big J15 plug is disconnected. That seems a bit suspect to me, but the manual reads like that is only for stopping runaway conditions.

I don't see anything else that would sense flame/heat.

Thoughts?

Neal

[Old-Biscuit]

Spark Electrode has dual purpose
High voltage for ignition
Return path for Flame Proving signal....change in current via flame rectification

Spark Electrode must be engulfed in flame and be CLEAN
*soot/carbon on electrode will inhibit the milliamp current that proves flame lit----clean with emery cloth
Electrode wire connection must be clean and tight at circuit board

**Spark Electrodes were not sold individually......part of the gas train assembly


The Atwood HE0601 had short production life.....helium based absorption fridge that Dometic dropped support for after they acquired Atwood
Parts are NLA/Out of production

The switch on the stack.....thermal switch that when it trips open stops all DC to circuit board due to overheating of boiler section



Hopefully cleaning up the electrode and connections will resolve the ignition issue
If not electrode then circuit board 'sensing' circuit


Here are some links to 'HE' manuals, parts etc
https://techsupport.pdxrvwholesale.c...twood-he-0601/

[mnopneal]

Thanks heaps for the reply, that clarifies a lot.

Now, IF, after cleaning as you suggest, and hitting the connectors with some De-Oxit, it still fails to recognize flame, how might we split the problem into parts and figure out what is wrong?

It reads like I don't want to place any test meter in circuit, because it's gonna have high voltage sparking, then not.

What if I disconnect the ignitor, put a couple of volts across it, measure current, and then put the ignitor end over a lighter flame? Would that tell me if it's the ignitor versus the control board?

Regards,

Neal

[Old-Biscuit]

Never try a 'trial for ignition' without spark electrode connected. That can damage the circuit board

You can check continuity of spark electrode to verify that the electrode and wire are intact

After cleaning electrode/wire connection:
If spark electrode fires during 'trial for ignition' (produces spark) but continues to fire after flame is present then that is a circuit board issue
If spark electrode fires, then stops after flame is present and then gas valve shuts down that is most likely spark electrode issue

Biggest issue......NO PARTS AVAILABLE

[mnopneal]

So, we cleaned the electrode. It was a bit sooty.

It is positioned above the slots in the burner assembly; no changes there. There is no choice on positioning without bending stuff.

It sparks and lights, so obviously we have continuity from control board to the electrode.

After cleaning, no change - it lights up, and keeps sparking, and then at the end decides there is no flame and shuts off.

I'm still puzzled as to the return sending path - I'm guessing it relates to resistance from the one electrical wire to the mounting, which is in turn grounded to the frame? I'm reading about 500K ohms between those, but it seems to vary wildly.

BTW, the electrode is an HY4-0003. This is available both from Amazon and from a couple of Ebay RV vendors.


https://www.amazon.com/Atwood-14068-...UE/ref=sr_1_10 $21

https://www.ebay.com/itm/Atwood-1406...-/224811835335 $13

It would be nice to do a bit more measurements, but I'm suggesting my friend risk the $20 and try replacing the cheaper component first.

regards,

Neal

[Old-Biscuit]

Flame Rectification/Flame Proving

The flame sensor is mounted on the burner box and is enveloped in flame.
Current flows from the sensor though the burner head to ground. Because the sensor is smaller then the burner head, current flows
in one direction.
The resulting pulsating dc current is considered rectified. The presence of pulsating dc current tells the integrated control board to continue
the heating sequence

Cheapest part to replace is that spark electrode
Typically if electrode continues to spark after flame is ignited then issue is with the circuit board

[mnopneal]

ok, 90% success with getting Atwood HE0601 fridge to run on gas again.

The replacement HY4-0003 ignitor/sensor had a different orientation w.r.t. the hold-down collar and the ignitor wire. The wire came off about 180 degrees from where it needed to be.

By re-orienting it and holding it down with vice grips for a good ground connection, the fridge fired up on gas and stayed lit.

A VERY BIG YAHOO!. Beats having to replace the control board.

Now, for a permanent fix - CAN WE BEND THE IGNITOR WIRE? IS IT LIKELY TO BREAK?

Or do we have to do something funky to bolt it down?

[Old-Biscuit]

The 'electrode' rod is hot formed and becomes brittle
Attempting to cold bend it may break it

Heat it with propane/butane torch then bend when red hot

Good Luck!

Might want to get another from Ebay as backup

[mnopneal]

oooh, good thing I had a cautionary bone in my body.

OK, heating red hot sounds a bit scary.

The problem is the metal collar which bolts it down is oriented wrong. If we cut off the heat-shrink tubing, can we just twist the collar around 170 degrees? Then put on fresh heat shrink?

[Old-Biscuit]

The 'wire' inside the red insulation goes inside the ceramic insulator and connects to the rod
Twisting it will break the wire......no more spark but more importantly no return path for flame proving signal

Best to modify mounting then trying to reinvent that electrode