Ignition coil hydrohot troubleshooting

[Al Lewis]

I have been fighting a stubborn diesel burner on my hydrohot for years. I broke down and bought a new ignition coil. I believe it to be fixed but more time will tell. The troubleshooting procedure that has been suggested by many did not work for me. That involves firing the coil 100 times. I believe it either works or does not. I did use the suggestion of one member of putting a clear plastic tube over the fuel nozzle and operating the unit to check for spark and fuel flow without causing a flame. Mine would fail to fire when cold. The temperature to fire kept getting higher over the years. I was finally able to confirm the no fire condition, then put a heat gun on it and get it to fire again. With this diagnosis I spent about $330 with suremarineservice.com and got a new coil. Note that this price is about half other quotes. They probably all come from the same source in Germany.

The electronics to fire the coil is encased in a hard epoxy. It is probably constructed using surface mount components. I believe with time and temperature cycles an intermittent contact is developed. Anyway that is my two cents worth. I hate to spend big bucks throwing parts at a problem unless I am confident in the troubleshooting and think I know what is going on.

[Tic Wilson]

My copy of the Hydro-Hot service manual says to remove the coil, disconnect the wires, and with the burner head out, apply 12V to the yellow lead and negative or ground to the brown wire and a spark should appear across the electrode tips.  I just did this on my unit and no spark.  I metered the coil with my digital meter and it shows an open coil.  I am hoping that a new coil will also resolve my ignition issue.

[Marty and Suzie Schenck]

Go to www.rvhydronicheaterrepair.com and join that forum (free). It is a wealth of information and new factory parts at a discounted rate. It has helped me many times and saved a bunch of$$$$$$.
Marty