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Randall, RVIA Certification
Category: RV
Satisfied Customers: 10279
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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JA: . What is your issue regarding?Customer: I

Customer Question

JA: Hi. What is your issue regarding?
Customer: I have a hydroflame 8520-II and having the same problem everyone else is. Random ignition. Following is what we've done:
JA: Sometimes things that you think will be really complicated end up being easy to fix with RV. The RV Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: replaced board, burner, fan motor, limit switch. Tested spark, system getting is getting fuel.
JA: Are you hoping to fix this yourself?
Customer: Ran with new components all day with no problem, then, starting in the evening time, the system would try to ignite but would not, consequently fan runs indefinately.
JA: Is there anything else important you think the RV Mechanic should know about your RV?
Customer: at night time, the system randomly lights, more often not tho.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the RV Mechanic about your situation and then connect you two.
Submitted: 5 months ago.
Category: RV
Customer: replied 5 months ago.
Additional info: I have also tested the sail switch. Other than changing the gas solenoid and orifice, everything in the heater has been either checked or replaced. Forgot to mention that the burner was also replaced.. Note: the main propane regulator has not been replaced.
Expert:  Randall replied 5 months ago.
This can be a result of low incoming DC voltage OR some AC ripple in the DC side from a failing converter OR low LP pressure at the tank regulator which should be checked and adjusted if needed at least once a year. IF you are still using an OEM control board that can be an issue. Those have a pretty high failure rate. Dinosaur Electronics makes a good one that is made in Oregon instead of China. Check those things first and we can dig deeper if needed. Any chance that wasps or mud dobbers got into the furnace? That is a big problem in my area. Hope that helps here. Please get back to me if you need more as all follow ups are included in our fee.
Customer: replied 5 months ago.
just tried a new regulator, no joy. also, the board was replaced with a dino UIBs. Board operating correctly according to onboard led. voltage is 13.2 plugged in, 12.9 on battery so input voltage is not a problem and dc would rule out ac ripple. The heater has been completely disassembled, cleaned and reassembled with new components (fan motor, limit switch, board, and burner. Gas orifice was inspected and cleaned. Sail switch tested. Also, board is triggering gas valve and ignition 3 times then locks out which confirms the limit switch and sail switch operation. Smell gas when trying to ignite.
Expert:  Randall replied 5 months ago.
IF the coils on the gas valve ohm out o.k. then the most probable cause is some debis like wasp's or mud dobbers nests inside that is messing up the air flow. That would keep it from igniting when all other parts are working properly.
Customer: replied 5 months ago.
I solved the problem. I adjusted the electrode to be 1/4" from the top of the burner, rather than the 1 1/4" than the factory distance. This results in immediate ignition upon first release of gas.
Expert:  Randall replied 5 months ago.
Not sure how that would happen. In rare cases I have seen debris off the coating on the inlet tubing come off and blow around inside and sometimes plug up part of the jet. If you still have any problems you might take that apart and check it. I think I have only had it happen twice. If the mixture is too lean due to any LP restriction, it will burn out the burner head in short order.
Expert:  Randall replied 5 months ago.
And one other thing I should mention. The measured DC voltage while good, doesn't preclude any AC ripple. You would have to set your meter on AC volts and check for that or did you? Any AC in the DC circuit will add to the DC voltage reading and must be also subtracted from that reading to see the total range on the sine curve. I have see this be a range of between 7 and 20 volts and control boards don't like that much variation. If you still have an older converter this is a real possibility.

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