Originally Posted by Lakescepter
2004 HR Scepter ISC350 Onan 7.5. Chassis batts are not charging from altenator, generator or solar. House batts are staying charged, with gen running have 14.68-74 at house batts but only 11.68 at chassis batts. any ideas where to look would be appreciated have no wiring diagram for system.
Lakescepter (Whats your first name?).
There are two charging circuits in an RV. The engine/Alternator charges the Chassis batteries, and the Inverter/Charger charges the House batteries.
The only connection between these two systems is the "Isolation Relay".
This relay puts both sets of batteries in parallel. Your AUX-Start switch activates this relay also.
Most coaches activate this relay when driving so that the alt will charge the house batteries. But when on shore power, each coach is different. My sons Fleetwood will activate the solenoid to keep the chassis batteries charged, but my Phaeton has a separate battery minder for the chassis batteries when on shore power (does not use the relay).
What sounds strange is that your chassis batteries are not seeing a charge voltage from either the alternator (normally a direct connection) or the generator/AC (connect thru the isolation relay). This may be expected for your coach...it is on mine.
I suggest you check that your isolation relay works. Make sure you measure both sides "BEFORE" you activate it. one side is house and one side is chassis. You should see two different voltages. The activate the AUX-Start and make sure the relay closes. Do this WITHOUT shore power. Just because this relay works, it does not mean the coach uses it while charging the chassis batt. from the house charging circuit.
When on generator, this is the same as shore power, the inverter/charger charges the house batteries. Solar also charges the house batteries. So these two sources rely on what ever circuit the RV uses to tie the batteries together(if any).
On the other hand, the alternator should be a direct connection to your chassis batteries. I would focus on that problem.
Alternators have a internal voltage regulator. So the "BATT" connection on the alternator should be directly wired to the chassis battery (maybe fused). See if you can measure the same chassis voltage on that terminal.
This will show the wiring connection is good.
Also check your chassis battery ground connection.
Let us know what you find..