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John deer · 08-16-2015, 07:19 AM

Shore power only works if the ignition switch is on. Generator only starts and works if the ignition switch is on. Turn off ignition switch and both stop working. 2002 phaeton. Any suggestions?

twinboat · 08-16-2015, 07:36 AM

Do you mean 12 volt items don't work, when on shore power, without the key on?

With the generator not starting, you may have your house battery switch off, your house battery cables dirty or your house battery is completely dead.

On some MH's, when you turn on the key, you interconnect the engine battery with the house battery. That would explain the generator starting.

You may also have a bad converter or one that needs to see 12 volts to kick on.

Check the house battery volts and connections. As a test, plug in, turn on key, wait 5 minutes to turn off key and see it things stay working.

Hope this helps.

luvlabs · 08-16-2015, 07:46 AM

Lots of things need 12V to operate. As you found out, your generator, lights (obvious), A/C units (thermostat is powered by 12V), and so on.

A couple of things you need to do - check the 12V On/Off switch. It is usually mounted with the other switches by the entry door. Turn that on and you can check real quick if it is working by turning on a light. If you still aren't getting 12V, check your batteries (you will need a multimeter).

If your batteries are fine, then you could be having a problem with the 12V solenoid that does the actual switching of the 12V when you activate the door switch. I'm not sure where it is located on your coach but a quick call to Tiffin Service on Monday should get you that information.

FIRE UP · 08-16-2015, 09:06 PM

Wow,
I must have been on the wrong planet for the first few decades of my life. I do not remember any motorhome EVER needing the ignition on or, a 12V source in order for SHORE POWER to work. And, other than needing a fully or, at least semi-fully charged battery to START a generator, I've also not ever heard of the need for any 12V source to keep it running other than maybe 12V for an electric fuel pump.

Now, I'm certainly not the sharpest tool in the shed but, I just can't remember ever needing my ignition in the coach on, to either start or run the Gen or, have the shore power be effective.

Now, I do know that, some, if not most, modern day fridges and thermostats need 12V to operate some of the circuit boards in the controls.

And, I'm certain ALL motorhomes are different but, just how much different, who knows? But, the basics to me are, if you plug in the shore power, 120VAC is now proceeding to and, right through most Inverter/Chargers, right to the 120AC panel which, is then dispersed through all the circuit breakers to the appropriate outlets. Or, if you have a gas coach, the shore power proceeds through the Converter/Charger and, right to the 120AC circuit breaker panel and, so on.

Where, may I ask, is the need for the ignition of the coach, to be in the picture?

There might be a simple answer to the OPs problem but, off the top of my head, it's not coming into mind right now. Maybe there's some sort of major solenoid that has to click into place, in order for the shore power AC to be allowed to go through, heck, I don't know. And maybe that solenoid is triggered, in some odd way, by the ignition, again, I don't know. I'm always learning something on this site.
Scott