Auxiliary start(?) question

[Widewader]

Can't remember for sure what it's called, but the button on the lower left side of the dash that's supposed to help start the engine on my 06 Greyhawk has me stumped. Last week, I went over to run the generator and there was no battery power. I jumped the generator off with my Jeep. Being a hot July day in Tennessee, I decided to start the V10 so I could run the AC. No battery power. With the genset running, I tried using the auxiliary start button. The engine didn't turn over and the generator died. I gave up and went home. Next day, I returned with two jumper cables. The Greyhawk is parked in covered storage with boats on both sides so I needed two cables linked together to reach the front of the motorhome. I started the engine, ran it for about 10 minutes, cut it off, and it wouldn't re-start. Started the generator and tried the auxiliary start button. This time, the generator didn't die. It stumbled, but kept running. BUT, the V10 only clicked. Turns out, the 2013 WalMart battery had to be replaced. Still wondering if the auxiliary start should have helped start the engine. How about it?

[Mnxtrik8r]

I believe the button you are referring to activates a relay that jumps the starting battery from the coach battery in the event the starting battery dies.

[Widewader]

Right. I knew that. I'm curious as to the reason it didn't help start the engine.
What should I have done or was the bad battery the stumbling block? I thought that was the main reason for it - to enable a start with a dead or weak battery.

[MadDad]

I found out the hard way that shore power doesn't keep the engine battery charged. It had ran down so far that a battery charger wouldn't charg it. I remembered the start button that you mentioned, and it started right up. Ley the engine run for about an hour, then shut it down and hooked the charger back up. AOK after that.

[Ont Pete]

I'm not an RV guy so I don't know exactly how they are set up but from what you said it sounds like both the engine battery and the RV battery were dead. These batteries do not charge up very much in 10 mins if they are stone dead which it sounds like yours were. It sounds to me like you were trying to draw power from 1 dead battery to start using the other. Anytime a battery goes completely flat they should be recharged fully using a battery charger, preferably a slow charger (in the case of the RV battery it should be charged with 1 when plugged to shore power) rather than the alternator. But my question would first be why were both batteries flat to start with? Did it sit for a long period or does it have a draw that killed them?

[LkptRvPilot]

Hi Wide,

I find the "Aux start" button almost completely useless. The GenSet is not powerful enough on its own to turn over the engine. The House/Coach battery is too far away, even when fully charged, to provide adequate amperage to turn over the engine (due to wire length/size).

In reality, its more of a "boost" button, where if your chassis battery needs just a tad bit more juice, you can borrow some from the house battery, but it will not work at all with a dead chassis battery.

In short, if you have a low or dead chassis battery, you are going to have to jump it.

[The Logans]

I had to use the Aux Start twice before I found out that shore power doesn't charge the chassis battery. Fortunately, the Aux Start worked like a charm both times. I just held the button in turned the key... it cranked very fast, and started right up. Whew, glad it was there!

Next purchase is a small solar trickle charger that sits on the dash, and keeps the chassis battery topped off. In the winter I keep it on a float charger.