Electrical Fire on Coleman A/C (or very close to one!)

[tppilot]

My 2005 Winnebago Voyage 33V has two Coleman roof mounted heat-pump A/C's (model 8534B876) which use a ceiling plenum assembly (model 8530-7332). The ceiling assemblys are equipped with a junction box (part number 7530A508). This junction box contains the compressor relay, a circuit board and various other components. It also is where the unit receives it's 110v power.

While connected to shore power, a strong burning smell began coming from the rear unit. Though the unit continued to run and blow cold air, it smelled too bad to continue using it, so we shut it down. The breaker did not trip!







The pictures are a bit blurry, but a close look will show that the black 110v supply's insulation is melted. The screw holding it to the terminal is welded to the post.

I cannot tell exactly what caused this meltdown, but can only assume the compressor relay overheated and caused the PC board to melt and short to the metal box.

A test of the shore power voltage showed a strong 110 volts from the supply.

Anybody want to guess what caused this and why the breaker did not trip?

Thankfully, we hadn't left the dog inside w/ the AC on and were there to shut it down (since the breaker obviously didn't do it's job).

[RV Wizard]

Most likely the problem was a loose connection of the 120 vac wiring on the board. Glad to hear no one was injured or worse. Take care and keep us posted.

[John Hilley]

The breaker will only trip if excess current is drawn for a period of time. A loose connection will cause heat at the connection point but not trip the breaker. Don't depend on breakers to trip for all problems.

[tppilot]

Thanks for your responses. I'll install the replacement and give it a good shakedown this coming Labor Day Weekend!

[AUSSI]

Had the same problem 2 yrs ago, cause was the set screw on the 110v supply terminal was not tightend at installation. An out off pocket issue for me, no one came good on it.

VIC (VE3IHK)
05 SUNRISE 33V WH
01 BUICK REGAL TOAD

[RV Wizard]

This is an example as to why you should, on an annual basis, check all of the electrical connections; especially at transfer switches, junction boxes on main power, and distribution panels. Heavier load applications are going to be the most critical. Good luck and every one stay safe.