12 volt system "cycles" when heater is running

Since you mentioned you have an inverter the unit is likely wired with the power going straight to/from the batteries for the inverter/charger (The inverter is most likley your charger as well)

Things like the salesman switch/battery disconnect are thus turned ON, because if they were not, shore power or not, you'd be in the dark (lights would not work).

It could be bad batteries but I put that low on the list.. I will stick with your choice of overload or bad breaker cycling,

To test for load

you need a DC clamp on ammeter,, Clamp the POSITIVE wire that feeds the coach, or the negative wire that does not go to the inverter, either one will give total amps to the coach.

Oh ... yes I've been relying on the wall panel indicator. Hmmm, I've really not looked at the battery switch. I'll have to check to see when I get back to the coach

That sounds possible.... but your 12v should still work fine off battery when the surge protector cuts power.

The battery switch is on, yes? Battery terminal voltage should be about 13.6 volts. The indicator in the RV is probably reading the fuse panel voltage not necessarily the battery itself.

Plugged into shore power. Discovered something interesting however, on the power pedestal the 110 side that powers our outside pipe wrap and some patio lights the CFI keeps popping off - I wonder if that in someway causes a surge (although I have a surge protector at the pedestal) and that somehow interferes with the 12 volts last night? Like I said today, there's no issue.

Are you plugged in or going off batts only?

Since you have an inverter.. This is a line drawing of how most motor homes with INVERTERS are wired

Inverter-~--Battery--Circuit breaker---Rest of 12 volt system including furnace

ON the other hand if you did not have an inverter it would look like this

Battery--Breaker---Rest of 12 volt stuff including both converter and furnace


What the problem is

You have one of two problems,, Eiteher you are drawing a bunch power on the 12 volt side with lights and such and when the furnace kicks in it trips the breaker due to overload.

or the breaker has gotten Weak with age, and what way say an 80 amp breaker is now a 30 amp breaker and see above paragraph

By the way, in the first line drawing ~ is a fuse.

OP: Well so far this morning no problems - no cycling - furnace running like a champ - voltage reading steady. Only thing I've not done is to test batteries independently / off the grid.

pianotuna wrote:
Hi,

You may have an automatic reset circuit breaker which is starting to fail.

It is also possible that the furnace fan is drawing a great deal of current.

Check the amperage draw if you can.

Also, make sure all battery and ground connections are clean and making good connection. It sure sounds like an automatic circuit breaker is turning off and on.

Hi,

You may have an automatic reset circuit breaker which is starting to fail.

It is also possible that the furnace fan is drawing a great deal of current.

Check the amperage draw if you can.

Batteries could be the problem if you are using them exclusively. If you are plugged into shore power, then it could be a converter problem.