Fenwal ignition module trouble

remodelingjunkie

hi everyone, I am working on a Jandy LXI pool heater, it uses a Fenwal ignition module (35-665942-113), last year I was not able to get it to provide 24 volts to the gas valve, It would measure 24 volts open circuit though, and dropped out as soon as I connected the gas valve to "close the circuit and put a load on it". So I ordered a new module, well, a used one and it worked for about a year. I now have the same problem so I simply ordered another one, which didn't work, seller sent me a replacement and that one is doing the same thing. I feel like I am missing something or are these units known to be unreliable? I did pull the flame rod which was pretty rusty, but I figured that only came into play once there was a flame to begin with. I also did test the gas valve with a test transformer and it pulls .62amps well below the 2 amp maximum listed on the fenwal.

Big Ed_4

You could have a weak ground ..

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1809744#Comment_1809744

Or a bad power wire connection. Clean all the contacts and terminals (don't worry — you can't clean them too much!) and check all the wiring for any breaks or bad spots in the insulation.

Bob Harper

As stated, grounding and connections. You need to scrub the grounding attachment point with emery or steel wool then do the same for all solderless terminals. I recommend only original Thomas & Betts for reliability even if $1/ terminal. Bill the customer. Re-crimp new terminals if need be. Scrub the flame rod and ensure it is engaged properly in the flame so you're getting steady flame rectification.

The only times I can remember a DSI/HSI board actually being bad I popped open the case and saw a burnt component on the board. Just my experience.

As for the line voltage, measure voltage from neutral to ground. If you're getting more than about 50 millivolts SC, you have a house power problem. Get a circuit analyzer like the Sure Test from Ideal. It can measure voltage drop and detect bootleg grounds. If you don't have clean power you'll be throwing parts at it forever. Compare the voltage drop line to the TH terminal against the line drop to neutral to see if its wired bass-ackwards off the tranny. Do you have about 18-30 VAC coming out of the tranny? Is the input amp draw about 300 mA with the gas valve energized. You can take a spare tranny and apply 24 vac directly to the valve to see what amperage it draws to open. Have you Ohm'd out the valve to see if the servo might be bad?

Interesting case.

F-35-66.fm (kidde-fenwal.com)

OldManwithStick

My question is did you replace it with the exact fenwal module or did your supplier provide you the Emerson replacement? (50E47U-843)

50e47tech.pdf

remodelingjunkie

So, it ended up being an "open" vent box fusible link, I used quotations because it was not an OL open, but just enough resistance that it would not throw the "Fuselink fault" I should have known better LOL.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1811322#Comment_1811322

My bet is it is riveted together and the rivets got loose/corroded.