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Open Roads Forum  >  Tech Issues

 > Dometic/Atwood Furnace AFMD30... grrr cntl board

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groundhogy

PA

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Posted: 03/06/22 12:42pm Link  |  Quote  |  Print  |  Notify Moderator

So as we discussed in another thread, i pulled the stove out and went to work cleaning lint out that may have been blocking air flow. I had complained of the flame cutting off/on during cycle.

I cleaned around any slatted vents in the enclosure.

I went outside, pulled the plastic cover, pulled lint out there. Also had one of those cheap $1 little paint brushes handy and used that to brush off static dust.

FURNACE NO STARTY....

Today i troubleshooted it to the control board.

12v is on the wire that plugs into board.
But when i attach it to the board, its zero volts.

No action on the little red LED.

Do you guys agree that its the board?
What Dinosar board do i order?

groundhogy

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Posted: 03/06/22 12:44pm Link  |  Quote  |  Print  |  Notify Moderator

Second question... just appeared in my mind.

How does something on that little board make big current? 12v go to zero and nothing is getting toasted?

groundhogy

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Posted: 03/06/22 12:50pm Link  |  Quote  |  Print  |  Notify Moderator

Something in the 12v line high resistance?

groundhogy

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Posted: 03/06/22 12:55pm Link  |  Quote  |  Print  |  Notify Moderator

Schematic on pg 8 of this manual.

https://forestriverinc.com/files/Component-Manuals/Heating%20-%20Air%20Conditioning/Dometic%20(Atwood)%20-%20Furnace%20Model%20AFM,%20AFMD%20Series%20Operating%20Instructions.pdf

The only thing in the 12v path is the little breaker switch.
Also I don’t understand how/why the thermostat wire is involved/connected in this ckt if anyone smarter than me can explain.

groundhogy

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Posted: 03/06/22 01:01pm Link  |  Quote  |  Print  |  Notify Moderator

Just shorted/bypassed the breaker switch.
Nothing

enblethen

Moses Lake, WA

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Posted: 03/06/22 01:35pm Link  |  Quote  |  Print  |  Notify Moderator

There is a small transformer on the circuit board that bumps the voltage way up to create the spark to ignite the propane.
Things like circuit board or gas valve can be bad that would affect the voltage readings.
Unplug the connector and check readings. Problem goes away, plug it back in. Disconnect the gas valve coil. Test again.
Manual
The power goes through the thermostat before getting to the furnace.


Bud
USAF Retired
Pace Arrow

2003 Chev Ice Road Tracker


enblethen

Moses Lake, WA

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Posted: 03/06/22 01:54pm Link  |  Quote  |  Print  |  Notify Moderator

Forgot to ask what type of thermostat you have. Pop the cover off and check if it is two or multiwire style.
Locate exact circuit board number on your unit, look on Dinosaurelectronics.com website. If not sure call them!
Should be this one. See if it looks the same!
Circuit Board

groundhogy

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Posted: 03/06/22 02:43pm Link  |  Quote  |  Print  |  Notify Moderator

Its a two wire thermostat

groundhogy

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Posted: 03/06/22 03:08pm Link  |  Quote  |  Print  |  Notify Moderator

Ok, I pulled the other wires off of the board - in case they were drawing down the supply voltage.
The board still appears dead.

enblethen

Moses Lake, WA

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Posted: 03/06/22 05:29pm Link  |  Quote  |  Print  |  Notify Moderator

I hate to throw parts at a problem!
Suggestion: Look at your water heater circuit board. It maybe the same. Switch them out to verify problem. If problem goes away, hooray! Order a replacement board. If it doesn't you have another issue.

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