Old Crow
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The Atwood 8516-IV furnace in my 01 Hawk has been failing to start combustion on the great majority of attempts. After each set of three attempts, it was going into the lockout condition (indicated by the LED code of 3 flashes, a 3 second pause, 3 more flashes, etc). I could do another set of attempts by setting the thermostat to minimum and waiting 60 seconds. After a few of these 3-attempt cycles, I'd finally hear it start combustion but then it would only run for six to seven seconds. And when it stopped, it did so abruptly and I thought I could hear the click of the gas-valve closing.
I called Atwood and talked briefly with a tech support guy. He suggested the most likely culprits were the circuit board (also known as the DSI or Direct Spark Ignition module) and the electrode/flame sensor assembly. He also told me many RV shops will test the board for free. And he noted the problem could also be caused by a bad connections, bad ground, low gas pressure (and others) but those two were perhaps more common.
I called up my local RV shop and they did indeed have the tester and would be happy to test my board for free.
When I took the board in for the test, the counter guy just pulled out the tester and ran the test in front of me there at the counter. He used one of the testers from Dinosaur Electronics ( http://www.dinosaurelectronics.com/IMT-12P_tester.htm ). When it passed, he said “Congratulations, you just saved $130.” Since the next thing on my list was the electrode/flame sensor and it was only $10, I bought one there.
When I pulled the old electrode assembly, I checked for the standard 1/8” gap and noticed the main electrode wire was loose in the insulator. The gap would vary from almost-none to nearly 1/4” just by touching the side of the terminal connector. The new electrode, on the other hand, didn’t move and had the standard 1/8” gap.
The new one is also different in that instead of a (male) slip-on terminal on the connection end of the electrode wire, it has a wire coming out of the insulator with a female slip-on connector on the end of the wire. The package also has what I thought at first was a jumper wire but it’s actually a replacement for the wire from the electrode to the coil on the circuit board. The older style part # 37057 was superseded by the newer-style kit (part # 34570).
With the new electrode in place I turned up the thermostat and this time combustion started on first attempt. And it has been starting on first try ever since.
Also-- Several months ago I had ordered a Frost Sentry non-programmable garage thermostat to replace my mechanical one, largely because of this thread: http://www.wanderthewest.com/forum/topic/9895-another-thermostat-thread/?hl=%2Bdigital+%2Bthermostat so I also installed that this week.
The install was very easy and the furnace appears to work properly with it but I do have one minor unresolved issue... the Fan Only button does not turn the fan on. The troubleshooting guide says that could be the gas/electric jumper and I realized I had not changed it from the default of ‘electric’ to ‘gas’. But changing it made no difference.
Also- The exploded-parts diagram for my 8516-IV says the board is part # 36716. The board on mine, though, is part # 37875 (the part number is on a sticker on the coil). I was considering ordering a Dinosaur Electronics aftermarket board to replace mine (before I had mine tested) and if I had gone by the diagram I would have ordered a UIB-S to replace part # 36716 when I really needed the Fan 50 Plus Pins model to replace part #37875. (note: it’s easy to miss the cross-reference chart-- it’s on the Ignitor Boards page and is marked “*** Ignitor Boards Usage Chart Link ***” ).
Also- The Fan 50 Plus Pins board has additional troubleshooting indications. My Atwood board doesn’t have a green indication at all but if the Fan 50 Plus Pins board doesn’t go green, that indicates a high-limit or sail-switch problem. See http://www.dinosaurelectronics.com/Instructions/Fan50PP_inst.pdf for more detail.
Also- to remove the board for testing or contact cleaning-- Carefully remove the cable connector and disconnect the wire between the coil on the board and the electrode behind the gas valve. Remove the wing-nut on one side of the board and the screw on the other side. Slide board out in its carrier. Remove board from its carrier by removing the screws in opposite corners.
Also - At first glance the electrode appears to be impossible to remove past the gas valve. It will indeed come out past the valve (and without removing the wires to the valve). It is a bit tricky to get the hold-down screws on the electrode back in place after you put the new one in.
-OC
PS- I have to write this stuff down cause I won’t remember what I did! Sorry for the wall of text.
I called Atwood and talked briefly with a tech support guy. He suggested the most likely culprits were the circuit board (also known as the DSI or Direct Spark Ignition module) and the electrode/flame sensor assembly. He also told me many RV shops will test the board for free. And he noted the problem could also be caused by a bad connections, bad ground, low gas pressure (and others) but those two were perhaps more common.
I called up my local RV shop and they did indeed have the tester and would be happy to test my board for free.
When I took the board in for the test, the counter guy just pulled out the tester and ran the test in front of me there at the counter. He used one of the testers from Dinosaur Electronics ( http://www.dinosaurelectronics.com/IMT-12P_tester.htm ). When it passed, he said “Congratulations, you just saved $130.” Since the next thing on my list was the electrode/flame sensor and it was only $10, I bought one there.
When I pulled the old electrode assembly, I checked for the standard 1/8” gap and noticed the main electrode wire was loose in the insulator. The gap would vary from almost-none to nearly 1/4” just by touching the side of the terminal connector. The new electrode, on the other hand, didn’t move and had the standard 1/8” gap.
The new one is also different in that instead of a (male) slip-on terminal on the connection end of the electrode wire, it has a wire coming out of the insulator with a female slip-on connector on the end of the wire. The package also has what I thought at first was a jumper wire but it’s actually a replacement for the wire from the electrode to the coil on the circuit board. The older style part # 37057 was superseded by the newer-style kit (part # 34570).
With the new electrode in place I turned up the thermostat and this time combustion started on first attempt. And it has been starting on first try ever since.
Also-- Several months ago I had ordered a Frost Sentry non-programmable garage thermostat to replace my mechanical one, largely because of this thread: http://www.wanderthewest.com/forum/topic/9895-another-thermostat-thread/?hl=%2Bdigital+%2Bthermostat so I also installed that this week.
The install was very easy and the furnace appears to work properly with it but I do have one minor unresolved issue... the Fan Only button does not turn the fan on. The troubleshooting guide says that could be the gas/electric jumper and I realized I had not changed it from the default of ‘electric’ to ‘gas’. But changing it made no difference.
Also- The exploded-parts diagram for my 8516-IV says the board is part # 36716. The board on mine, though, is part # 37875 (the part number is on a sticker on the coil). I was considering ordering a Dinosaur Electronics aftermarket board to replace mine (before I had mine tested) and if I had gone by the diagram I would have ordered a UIB-S to replace part # 36716 when I really needed the Fan 50 Plus Pins model to replace part #37875. (note: it’s easy to miss the cross-reference chart-- it’s on the Ignitor Boards page and is marked “*** Ignitor Boards Usage Chart Link ***” ).
Also- The Fan 50 Plus Pins board has additional troubleshooting indications. My Atwood board doesn’t have a green indication at all but if the Fan 50 Plus Pins board doesn’t go green, that indicates a high-limit or sail-switch problem. See http://www.dinosaurelectronics.com/Instructions/Fan50PP_inst.pdf for more detail.
Also- to remove the board for testing or contact cleaning-- Carefully remove the cable connector and disconnect the wire between the coil on the board and the electrode behind the gas valve. Remove the wing-nut on one side of the board and the screw on the other side. Slide board out in its carrier. Remove board from its carrier by removing the screws in opposite corners.
Also - At first glance the electrode appears to be impossible to remove past the gas valve. It will indeed come out past the valve (and without removing the wires to the valve). It is a bit tricky to get the hold-down screws on the electrode back in place after you put the new one in.
-OC
PS- I have to write this stuff down cause I won’t remember what I did! Sorry for the wall of text.
