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Topic: Voltmeter drop to ten then rose again (Read 438 times) previous topic - next topic

Voltmeter drop to ten then rose again

After leaving Gold Canyon headed to Tuscon today I noticed that my dash voltmeter had dropped to 10 V. I engaged the boost switch that brought it up to 11V. Arriving in Tuscon I set up an appointment with a repair shop for tomorrow morning. As we were heading to the KOA the meter rose to 12 V, then just a hair past. It would normally run somewhere just above the 13V mark.

Any ideas on what I should start looking at before investing in the pros?

Thanks,
Len
Len and Deb Speiser
1999 U270 36'
2017 Jeep Wrangler Unlimited
You're either on the bus, or you're off the bus!--Ken Kesey
If you're lucky enough to live in a bus, you're lucky enough!

Re: Voltmeter drop to ten then rose again

Reply #1 –
Len,

Check voltage at the chassis battery to determine if this is a gauge or charging issue.

If chassis battery voltage is also down, the problem is with with alternator, battery isolator or wiring to alternator.

Start by verifying that all the wires at alternator and isolator are clean and tight, particularly the small sense wire.  If all OK, let us know and we can walk you through an alternator/isolator diagnosis (assuming you have a digital voltmeter).

We plan to be in Tuscon in late Jan.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Voltmeter drop to ten then rose again

Reply #2 –
Check the dash relay, my be just loose nuts. ^.^d
1994 U280
Build #4451
"If everyone is thinking alike, then somebody isn't thinking"

Re: Voltmeter drop to ten then rose again

Reply #3 –
From my own experience follow Bretts suggestions. You may also want to load test your batteries. I had two bad batteries.
1995 U320 40', 2013 chevy sonic toad, my real love are corvettes have owned 30

Re: Voltmeter drop to ten then rose again

Reply #4 –
Alternator belt tight? Squealing?
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Voltmeter drop to ten then rose again

Reply #5 –
Reply to all...
Thanks for the input. I checked the belt, wires to the alternator and connections there. I was not able to do any testing with digital meter yet given the time and circumstances. It does give me some things to start with tomorrow.

This forum is invaluable and I really do appreciate everyone jumping in to help.

Len
Len and Deb Speiser
1999 U270 36'
2017 Jeep Wrangler Unlimited
You're either on the bus, or you're off the bus!--Ken Kesey
If you're lucky enough to live in a bus, you're lucky enough!

Re: Voltmeter drop to ten then rose again

Reply #6 –
Len,

Let us know if you have to drive before diagnosing and fixing the issue.  There are work arounds using the generator, inverter/charger and boost switch to keep batteries charged.  I would NOT recommend driving if voltage is low-- the engine and transmission computers need good voltage to operate.

A digital voltmeter reading on the chassis batteries with engine at 1000+ RPM will quickly help you determine the issue.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Voltmeter drop to ten then rose again

Reply #7 –
Quote from: Hammer2100 –
Check the dash relay, my be just loose nuts. ^.^d

I had a similar problem and found that the Dash relay was not allowing voltage to go through. Check the voltage on both sides of the relay when the ignition is in the on position, should be close to equal. Mine had dropped to <9 volts  going across. It is located under the dash behind and below the speedometer.  ^.^d 
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Gerry & Brenda
CHARLOTTE HARBOR, FL
1994 Grand Villa - # 4466
U300 Unihome - 6V92 Detroit
4 speed Allison - Jake Brake