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Topic: Voltage fluctuating in the cockpit (Read 972 times) previous topic - next topic

Voltage fluctuating in the cockpit

94 U280.  I had an overcharging issue with the coach batteries while running engine and genny. I decided to upgrade the Freedom 25 (inverter never worked does now:) to a Magnum 2812 and replaced the Isolator (bad) with a heavy duty manual Perko On/Off as Mr. Wolfe suggested. With the manual switch off and coach running I have good voltage to the chassis no issues. In the on position coach running I am getting a charge to both battery banks without fluctuation, but the chassis power beyond the batteries fluctuates wildly and suddenly from correct to low voltage and back up. The dash gauge is working verified. I do not have any electrical drawings neither did FT for this coach. I have a drawing for the electrical connections at the isolator panel and a few others I have found here. Bad Boost Solenoid? Any Ideas? Thanks, Ricky
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #1 –
I'm guessing a bad, corroded, or loose connection somewhere between the batteries and your dash gauge.

I don't think the boost solenoid would have anything to do with a wonky voltmeter reading.  Or did you mean to type ignition solenoid?

On our coach, the voltmeter gets it's hot feed from the "WARN LTS GAUGES" fuse in the fuse block under the dash cover.  That fuse is powered off the IGN side of the ignition solenoid under the dash cover.  The ignition solenoid gets power from one of the three 90A circuit breakers (the one on the left) on the 12 volt panel in the main storage bay (under the white fiberglass cover).  That circuit breaker is fed directly off the engine (start) battery post on the isolator, which is fed from the "engine" post on the boost solenoid, which is fed by the engine (start) batteries.

Since you replaced the isolator with a manual switch, I would start at that switch and work forward towards the gauge, checking connections and voltage at each connection point.  See if you can determine where the fluctuations originate.

All of this assumes, of course, that your coach is wired like ours.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Voltage fluctuating in the cockpit

Reply #2 –
Chuck thanks for the reply. This is all while the engine is running. What confuses me is that all works fine when the manual switch is off. With the manual switch off the alternator is charging the chassis batteries only plus running all things that the chassis needs. In other words all 12v power that was connected on the fourth or far right post of the replaced isolator is wired together. The only thing added to the circuit when the switch is in the on position is the house batteries. I had 3 volt meters checking voltage at the house, chassis batteries and the dash to verify. Both battery banks were charging, but the voltage at the dash would drop to zero. All the warning lights would flicker and then all would go back to normal.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #3 –
If dash voltage is fluctuating, but voltage at the batteries are not:

Check voltage at the battery side of the IGNITION SOLENOID (under dash) and then at the "out" side.
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: Voltage fluctuating in the cockpit

Reply #4 –
My guru buddy pulled my dash gauges wires off them and recrimped the push on ends and reinstalled the wires.

More stable readings. 

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Voltage fluctuating in the cockpit

Reply #5 –
Quote from: wolfe10 –
If dash voltage is fluctuating, but voltage at the batteries are not:

Check voltage at the battery side of the IGNITION SOLENOID (under dash) and then at the "out" side.
Brett,
I actually had 3 different meters running at the same time and one was on the battery side of the ignition the other two on the battery banks.
The fluctuation only occurs when the coach batteries are in play ( switch in the "ON" position).
I road tested for about 30 minutes last evening with the battery switch off no fluctuation and everything works as normal.
Maybe I just misunderstood the wiring. I have attached a photo from a another post not mine but identical, indicating how I wired the switch. Did I get it wrong? Sorry I did not mark the B+ coming from the alternator. It is also on the "off" side of the switch.

Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #6 –
Ricky,

So you have BOTH the diode based battery isolator AND a mechanical ON-OFF switch??  If so, why?
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: Voltage fluctuating in the cockpit

Reply #7 –
Quote from: wolfe10 –
Ricky,

So you have BOTH the diode based battery isolator AND a mechanical ON-OFF switch??  If so, why?
Brett,
No sir the isolator is removed it was bad. I was trying to indicate which wires I put on the different terminals on the switch.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #8 –
Ricky,

OK that sounds better-- had me confused for a minute there.

Wiring on the ON-OFF switch:
One lug to chassis battery and alternator B+
Other lug to house battery.

Then sense wire to either the chassis battery lug or other place with the same voltage reading  as the chassis battery (so battery or any other location with large-gauge wire connected to it).
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: Voltage fluctuating in the cockpit

Reply #9 –
Brett,
I am at the coach now trying to sort this out. I do not have e drawings only the isolator panel dwg from a 92. I am a 94. I have a 4 wire OEM  Leece-Neville 160 amp alt. I cannot find a sense wire coming down from the alt.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #10 –
Ricky,

With 4 wire alternator, you will have a sense wire-- or at least should.

The 4 wires:

B+
ground
sense
ign

But, as we have seen many times, you may not have an OE set up alternator on it.

Now with no diode-based isolator, the sense wire COULD be connected to B+.  And that works, as long as there is no resistance between B+ and batteries-- with just an on-off switch, there is no voltage drop (assuming good connections and adequately sized wire) between alternator B+ and chassis battery.

And, yes, if aftermarket alternator with no sense terminal, your set up should still work (it would be the same as connecting sense wire to B+).
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: Voltage fluctuating in the cockpit

Reply #11 –
The B+,grd and the ignition are accounted for. 4th wire/terminal goes internal to the alt. Should I pull a wire from here down to the off side of the switch as a sense wire? Remember when the switch is in the off position everything works as designed. The alt charges correctly to the chassis batteries and no issues in the cockpit. My only issue is in the on position the cockpit goes wonky.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #12 –
Ricky,

NO, quite likely you do not have a 4 wire alternator set up.  If the sense wire goes internal, it is the same (unless they really screwed up) as attaching it to the B+ terminal.

And since you do not have a diode-based isolator, it should work, providing the correct voltage to your batteries.
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: Voltage fluctuating in the cockpit

Reply #13 –
Here is the crux of the matter (from your first post):

" With the manual switch off and coach running I have good voltage to the chassis no issues. In the on position coach running I am getting a charge to both battery banks without fluctuation, but the chassis power beyond the batteries fluctuates wildly and suddenly from correct to low voltage and back up."

So, what is happening "beyond the batteries"?  All I can think of is bad connection or ?breaker? making and breaking!
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: Voltage fluctuating in the cockpit

Reply #14 –
Brett,
The problem is when I bring the house batteries into play by turning the switch to the On position. This is when I get the wonky cockpit. In the off position all is well. I road tested the coach in the off position for 30 minutes or so no problems. No loose connections that I have found under the dash, at the former isolator panel or in the main bay panel.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #15 –
Thanks Brett for all your help!!! I took everything apart and double checked all connections. Did a couple of percussion repairs and all seems to work. No road test. That comes tomorrow. I'll let everyone know if I find something.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #16 –
Went ahead and changed the Ign. Solenoid as you guys suggested. I didn't like the voltage across with a load on it. The fluctuation while the battery switch was in the On position is what got me even though I could physically see the cable only went to the house batteries. Coincidence I guess. It's hard to diagnose without e dwgs. For all I know the Flux Capacitor could have exceeded it's 1.2 Jigawatt capacity. The road test went fine. Fingers crossed. Thanks again for all the help.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU

Re: Voltage fluctuating in the cockpit

Reply #17 –
Sorry. I had it completely backwards on the Flux Capacitor. The minimum requirement is 1.21 jigawatts to get the Flux Capacitor to fire.
Ricky Pitts
1994 U280W SBI 
8.3 Cummins
Allison MD 3060
Build 4492
Toad: '14 JKU