Furnace working intermittently – SOLVED!

[Sharps OTP]

I found some threads on this topic through searching but was unable to post a reply due to the age of the last post.

I recently solved my furnace problem and wanted to contribute how I did it in case anyone else comes across a similar issue.

I have a Suburban NT-30SP furnace that was working intermittently. When it wasn’t working, the blower never came on when the thermostat called for heat. Nothing happened at all. Of course, this would happen on cold nights in remote locations.

When the furnace did work, it seemed to come on while driving or shortly after a trip. I thought maybe I had a loose power connection or a bad controller that would somehow “reengage” itself after bumping around down the road. However, no amount of banging the furnace on cold evenings ever produced any results!

I spent several hours searching the internet and came across several excellent troubleshooting guides, however, none of them addressed the specific problem that I had, hence my post here. I certainly learned more than I ever thought I would about furnace systems along the way!


It turns out that my RV battery charger stopped working and the house battery would slowly drain until it fell below 12 volts. There was not enough voltage at the thermostat, so the relay would not heat up enough to close the circuit and trigger the blower to start and complete the sequence to cycle on. As soon as I charged the house battery with a portable charger, the furnace works perfectly. I learned that even when the RV is plugged into shore power, the furnace still operates on 12 volts from the house battery. Since the battery wasn’t charging, it kept running down and couldn’t power the furnace.

The reason the furnace was working while driving, or shortly after completing a trip, is because the alternator was charging the batteries.

So one more thing to add to the troubleshooting… check your house battery voltage and make sure your battery charger is working.

I hope this helps someone. Now to figure out why the battery charger stopped working!

[JohnRR]

Thank you.

["007"]

Welcome Sharps OTP to irv2.
You have probably fixed possible other problems with your new 12V battery.
All your control boards need a good 12V battery to operate the control boards in water heater, fridge, AC's and your furnace.
Here is a good link to explain your RV electrical systems.
Thanks for your first informative post, enjoy the forums.
You did right post a NEW THREAD, posting on old thread may get lost to quickly for people to see your results.