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spankyjr1, RV Mechanic
Category: RV
Satisfied Customers: 2611
Experience:  I have been a mechanic/ technician for over 30 years working on gas,diesel,engines drive train,and electronics.
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1995 Tioga - I replaced the engine battery and both house batteries

Customer Question

1995 Tioga - I replaced the engine battery and both house batteries at the same time. When I started the motor the engine battery boiled a little bit, the amp dash light turned on and the dash volt gauge maxed out. Also, a high pitched whining came from, what sounded like, the fuel tank. I drove to Autozone to get it checked out (no fuel problems on the way despite the high pitched whining) they said the alternator checked out ok and confirmed the volts were high - they were puzzled. I got in to leave and all operations went back to normal. Went camping with full hook ups, no issues until I went to use the water pump at the dump station. That's when I found out the brand new house batteries were dead, never took a charge while plugged in and were also drained. This is Sunday and I'm leaving with my family Friday to dry camp. This can't be the first time this has ever happened so aim hopeful for a quick answer with a quick fix.
Submitted: 2 years ago.
Category: RV
Expert:  spankyjr1 replied 2 years ago.
Hi, my name is ***** ***** you for your question.
Sorry for long delay.
Would you still like some assistance with this?
Let me know
Customer: replied 2 years ago.
Expert:  spankyjr1 replied 2 years ago.
This is not a cut and dry issue,, but I have seen similar issues on other vehicles.
When a alternator overcharges like this,like it did to you,, it is the voltage regulator inside the alternator that got stuck,, in full output mode.
When it does that it can cause all other kinds of electrical issues.
So your question is two part,, first you do need a new alternator.
The output or voltage is controlled by the alternator, nothing else.The only other thing that could cause this is a shorted battery,, and yours is new,,,a alternator can come and go (cause voltage spikes) but once a battery is shorted it does not become un shorted.
The second part is not charging house batteries,, we will need to diagnose further but after you replace alternator, or you can cause more damage if not fixed first.
When replacing alternator disconnect negative battery cable before removing any wiring to prevent other problems,,follow positive battery cable and it will go to a charge solenoid and starter solenoid,,that solenoid on firewall is what allows house batteries to be charged while driving down the road,,they are cheap, so I would just get one (but don't replace yet) at same time as you get alternator.
Once you get this far you will need a volt/ohm meter to go further to do some testing.
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