Foretravel Owners' Forum

Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: CAPEHORN31 on December 31, 2016, 02:42:29 pm

Title: Relay bad ?
Post by: CAPEHORN31 on December 31, 2016, 02:42:29 pm
While driving the alternator charges at normal voltage + or - 13.5 vdc .  When I crank the generator the charge voltage from the alternator goes to 0 vdc.  Turning the generator off restores the normal charge voltage from the alternator.  I don't think this is normal , so the question is this,  Relay bad or some other problem. 
Title: Re: Relay bad ?
Post by: craneman on December 31, 2016, 02:58:07 pm
Voltage should be higher from the alternator 14.2-14.4 and also some other problem with no voltage with  the generator running. I am sure someone will have some idea of what is going on.
Title: Re: Relay bad ?
Post by: wolfe10 on December 31, 2016, 04:20:09 pm
This gets into a very sensitive (electrically speaking) discussion.

The source WITH THE HIGHER VOLTAGE will be the charge source assuming it has sufficient amps to reach that voltage.  So, it may be the inverter/charger when in bulk mode and likely absorption mode, then switch to alternator when inverter/charger drops to float mode.

Absolutely normal.
Title: Re: Relay bad ?
Post by: Barry & Cindy on December 31, 2016, 07:53:29 pm
So where are you reading voltages from?
Title: Re: Relay bad ?
Post by: FourTravelers on January 01, 2017, 12:28:36 am

Good question.....
The dash gauge should always read the chassis or starting battery voltage, less any voltage drop associated with the wiring to the gauge itself.
Title: Re: Relay bad ?
Post by: CAPEHORN31 on January 03, 2017, 03:58:44 pm
I found the problem!!!!!  When I completed the alternator sense wire modification , I attached it to the house battery isolator terminal.  This caused a difference in potential in the 12vdc as sensed by the alternator.  I reattached  the sense wire directly to the + terminal on the chassis battery.  Now the alternator charges the chassis batteries all the time weather the generator is running or not.  Thanks for the help. 
Title: Re: Relay bad ?
Post by: Don & Tys on January 03, 2017, 05:01:30 pm
Thanks for the follow up! I always appreciate the closure when someone solves the problem...
Don
Title: Re: Relay bad ?
Post by: wolfe10 on January 03, 2017, 05:14:27 pm
Yup, with the alternator sense wire on the house bank, with the generator running and inverter/charger charging, the sense wire tells the alternator to do nothing.  And unless the boost switch is on, the chassis battery is NOT charged from the inverter/charger.

So yes, having the sense wire on the house bank and inverter/charger charging (only) the house bank, the chassis battery will be "neglected".