Bizarre electrical issue

Any current changes in the supply negative of one device will have an unwanted effect in the other two devices. IMO

The clock may be sharing the same DC POSITIVE and NEGATIVE wires as the furnace. The clock should be getting DC power from the DC distribution source with its own + and - wires and not be hanging downstream from the furnace.

PS: It is the NEGATIVE wire that is the real culprit as it may be in a ground loop configuration when it shares the DC NEGATIVE wire with the furnace.

wa8yxm wrote:
It can happen the voltage will drop (Can happen.. WILL HAPPEN) and it may drop below the clock's cut off voltage, causing the BEEP, and weird action.

I'm going with that. I'm also suggesting you check the condition of your house battery.

Thanks so much for those ideas. Sounds logical that the clock might be on the same fuse as the furnace. There is not a separate 12v fuse labeled "clock" on the house 12v panel.

If that turns out to be the case, then I suppose the situation is not so weird afterall :)

Ok I think I have a clue.. The clock is an automotive type (Dash Clock) and it runs on 12 volt DC, not 120volt A/C.

SO DOES THE FURNACE

When that blower kicks in the draw on the 12 volt system is kind if impressive, IF the battery terminals are a tad in need of cleaning, Or if the battery is down at all, (of course plugged in one would assume it's full up) if the connections to the converter are tarnished.. It can happen the voltage will drop (Can happen.. WILL HAPPEN) and it may drop below the clock's cut off voltage, causing the BEEP, and weird action.

If you can confirm this (use an analog multimeter and watch the 12 volt line as the furnace kicks in) I have assorted cures.

First though, Clean the battery connections. IF that does not fix it, PM me.

2chiefsRus wrote:

Janss wrote:
I have a built in digital clock in my motorhome by the bed. It seems whenever I turn on the gas furnace, it affects this clock. After the furnace starts running, the clock sounds one long beep and the time changes. This morning the display showed 0:02. Then awhile later it showed 52:08. Just weird. The clock display is fine before the furnace gets turned on. I'm plugged in to shore power.

Any ideas?

Did you buy this rv used? Maybe a previous owner wanted to know when the furnace kicked on because they were worried about using too much battery while drycamping?

What purpose would that serve? If someone was worried about the furnace starting I would think turning off the thermostat would be preferable to being woken up when it starts.

I'd bet that it's wired to the power for the furnace fan and the voltage drop causes the clock to reset.

Try removing fuses until you find the one that turns off the clock, reinstall the fuse.. does the clock make the same noise? Also see if the furnace will operate with that fuse out. If it's on the same branch circuit, you could try installing a capacitor and diode in line with the clock that might buffer the voltage drop enough to keep the clock operating. This link has good information, Discussion on capacitors to buffer voltage drop

Janss wrote:
I have a built in digital clock in my motorhome by the bed. It seems whenever I turn on the gas furnace, it affects this clock. After the furnace starts running, the clock sounds one long beep and the time changes. This morning the display showed 0:02. Then awhile later it showed 52:08. Just weird. The clock display is fine before the furnace gets turned on. I'm plugged in to shore power.

Any ideas?

Did you buy this rv used? Maybe a previous owner wanted to know when the furnace kicked on because they were worried about using too much battery while drycamping?

That is weird. Did you check the wiring to the clock? Maybe it's wired to the furnace control