Alternator doesn't charge house batt until press emerg start

I get passed on highways by cars running on emergency spare tires at 80 mph. Just because I don't see them do somersaults off into the canyon does not mean the practice is the most intelligent. Hell my uncle in Montana controlled a pedestal grinder with a foot dimmer switch, and down here an English National Geographic magazine stands a good chance of being dismembered in an outhouse. A friend loaded his '50 Chevy pickup with three and a quarter tons of asphalt and limped six miles to his house to pave his driveway. IT WORKED! Is this abuse "recommended"?

Relays have ratings. The ratings including duty cycle should be obeyed. The only constant duty 12-volt relay I know of rated for 400 amperes break costs around two hundred dollars. "It Works!" is probably the biggest screw-up in the English language. It leads to "It Doesn't Work!" and that is guaranteed to happen at the worst freakin' possible time.

Do it right por favor. Find the ratings and obey them. BTW a hot non gear reduction starter motor starting say a 454 Chevrolet engine at 20 degrees can draw in excess of 400 amperes inrush and break. Guesswork leads to disappointment.

jayhorowitz wrote:

ksg5000 wrote:
In my Fleetwood Jamboree the isolator solenoid should engage when you turn the ignition key - you may have wiring or fuse issue. When I had similar problem I just ran a wire from an empty slot in fuse box through fire wall grommet to the solenoid - the fuse slot of use energized with key turning so it was a quick/inexpensive fix.

Clever fix. Did that mean running a wire all the way from the engine power distribution center to the house battery compartment? ...

As I recall I purchased a "piggyback" fuse and used the radio fuse slot - mine was located near the drivers left knee - ran a wire through a nearby grommet. My rig had an old fashion battery isolator solenoid with 3 lugs - the middle one was used to power up the solenoid and that's where I attached the wire.

ksg5000 wrote:
In my Fleetwood Jamboree the isolator solenoid should engage when you turn the ignition key - you may have wiring or fuse issue. When I had similar problem I just ran a wire from an empty slot in fuse box through fire wall grommet to the solenoid - the fuse slot of use energized with key turning so it was a quick/inexpensive fix.

Clever fix. Did that mean running a wire all the way from the engine power distribution center to the house battery compartment?

Can you tell me which fuse would operate the isolator solenoid? Would it be in the engine power distribution box or in the fuse box by my house battery?

I'll be at the RV tomorrow and will look into the alternator output voltage, potential wiring weirdness, and whether there is a delay unit.

Thanks for everyone's help! I'll report back as soon as I have more information.

In my Fleetwood Jamboree the isolator solenoid should engage when you turn the ignition key - you may have wiring or fuse issue. When I had similar problem I just ran a wire from an empty slot in fuse box through fire wall grommet to the solenoid - the fuse slot of use energized with key turning so it was a quick/inexpensive fix.

MrWizard wrote:
sounds to me like its been rewired

the EMG start relay is usually NOT a continuous duty relay and would normally burn out in short order
also NOT normally a latching relay

normal operation would have included a diode based isolator to do the battery charging and a light duty starter type solenoid/relay for the emg start

you can change this system back to factory, but i see no problem with it the way it is , Except for remembering to push the Button to start the process

The emergency start solenoids are indeed for continuous duty. They sometimes do dual duty on some motorhomes. They engage when you push the Start Boost button and release when you let go. Then, depending on the model RV, there is either a simple Ignition activated wire that keeps that solenoid closed for charging on the coach batteries, or it has a BIRD type system that supplies the 12 volt signal to close the solenoid to charge the coach batteries. The CHARGE rate is a LOT less than the amp draw when engaging to start the chassis engine. Most motorhomes use the same solenoid for both purposes. Doug

My coach has about a 30 second delay before the isolator solenoid engages. It's possible that you are not waiting long enough for it to engage or the delay circuit is shot.

sounds to me like its been rewired

the EMG start relay is usually NOT a continuous duty relay and would normally burn out in short order
also NOT normally a latching relay

normal operation would have included a diode based isolator to do the battery charging and a light duty starter type solenoid/relay for the emg start

you can change this system back to factory, but i see no problem with it the way it is , Except for remembering to push the Button to start the process

Is there a small device near the solenoid that has these words on it?

You may need to trace the wires that go to the small terminals on the side of the solenoid. The large terminals are the ones that actually connect the batteries together.

It sounds like the IRD is not putting out enough voltage to close the solenoid, but will hold it closed if activated by the aux start switch.

What is the actual voltage being output from your alternator? Is it lower than in the past?