Won't start off engine battery

[FrozenFour]

Alright my motorhome won't start off the engine battery but starts when I switch it over to the house batteries. I have had the battery tested and it is good, so am I looking at a bad altenator?

[mchero]

After charging the battery FULLY check the voltage on the battery before you start the rig.

While running check the voltage again, did it go up? Should show 13 to 14 volts when the engine is running, if not then your not getting any output form the alternator.

RM

[dougrainer]

FrozenFour wrote:
It is a 2003 Fleetwood Tioga 29V, I had the battery tested at Auto Zone and they told me it was pwefectly good. I brought it home and fully charged it and once I replaced it in the motorhome there was still no power. It does charge the battery when running. Sorry I am trying to be as detailed as possible but I am mechanically dumb!!!

1. It is IMPOSSIBLE to test a discharged/DEAD battery and declare it good or bad. You stated Auto Zone tested it, Unless it was charged, they cannot state it was good or bad.
2. Your Alternator has NOTHING at all to do with starting a vehicle. ALL it does is keep the battery charged fully while driving.
3. You have a problem with the Positive and negative cable hook up on your chassis battery. THAT is where you need to start. One of those 2 cables is not connected to the Engine and/or frame (Negative usually goes to the frame/engine block. Doug

[FrozenFour]

It is a 2003 Fleetwood Tioga 29V, I had the battery tested at Auto Zone and they told me it was pwefectly good. I brought it home and fully charged it and once I replaced it in the motorhome there was still no power. It does charge the battery when running. Sorry I am trying to be as detailed as possible but I am mechanically dumb!!!

[bdpreece]

Probably need more information such as type of motorhome etc, happens every time or only after being parked. You say that the battery has been tested but is it up to full charge? On my coach ,08 HR Endeavor there was a charge relay that was bad and even though the battery was good after being parked for a week or so the battery was too low to start the coach.

[Tom_Barb]

FrozenFour wrote:
Alright my motorhome won't start off the engine battery but starts when I switch it over to the house batteries. I have had the battery tested and it is good, so am I looking at a bad altenator?

Have you checked all the connections from the chassis battery to the starter?

Have you had a high rate discharge test done?

Place an external battery charger on it over night, see if it starts on a fully charged battery. but your coach should charge the chassis battery too, does it ?

If you get it started, run it see if the alternator charges the chassis battery.