Voltage at battery goes over 16.6VDC when generator on

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- Brian Stirling
  
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posted
20 years ago

Thu, Jan 22, 2004 4:24 AM

I just purchased a 1990 Pace Arrow motor home and discovered a problem with the Onan GenSet. The first night I tried to start it it wouldn't start -- slow turn over. This morning I hooked up a DVM to the batteries and it was about 12.03V without any load and with the shore power and generator off. When I tried to start the generator it did the slow turn over thing and when I checked the DVM I found the voltage had dropped to about 8.5V during the attempt (DVM set to record min/max). I then hooked up the shore power and 30 minutes later I was able to start the generator without much problem. I disconnected the shore power cable and went to the store to get some engine start spray for future use. When I returned about 45 minutes later I found the voltage at the batteries was over 16.6V. This is not good!

I then looked through the manuals that came with the Pace Arrow and found a schematic that is a bit confusing. I can see a reference for a voltage regulator (VR1) and there is also a little board with the rocker start/stop switch and on that board is a diode looking device labeled (VR1). The VR1 on the board does not look beefy enough to be the unit controlling the field coil on the generator so I have to presume the real voltage regulator is NOT on the little board -- right?

One more thing, if I have the generator running and the batteries are driving up towards 16+V if I turin off CB1 the voltage indication at the batteries drops right down. I would not think there is a separate AC powered charger being driven by the generator in addition to the one that seems to work just fine when power by shore power.

Wait a minute, I found another manual (Parts Manual) that indicates there are three different revs of board (300-3056, 300-3484-01, and

300-3687-01) that is referred to as (Board, Printed Circuit) with the 300-3056 specified as (Without Capped AVR Regulator), 300-3484-01 as (With Capped AVR Regulator) and 300-3687-01 as (Single Phase - Begin Spec G). In addition, there is also a part called (Regulator, Voltage) and there are two part numbers listed (305-0809-01 = 60 Hertz) and (305-0809-03 = 50 Hertz).

I would guess that the voltage regulator on the little board is for the DC charging and the other voltage regulator, either 50 Hertz of 60 Hertz is for the AC voltage regulation -- right?

If this is so then I probably need to replace the little board. If so, which version of the board should I get? The board that was in there has two numbers on it. On the silk screen is (332-3112.A) and on a label with what looks like a barcode is the number (300-3763-01-FS-0186156G16). If I read this correctly the board is a (300-3763-01) and that does NOT match any of the three listed in the manual.

Here's the full info for my GenSet:

Onan Emerald III GenSet Model#: 6.5NHEFA26100G Serial#: B900298288

If anyone can recommend a coarse of action here I'd be very thankful.

Thanks,

Brian Stirling

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- Michael A. Terrell
  
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posted
20 years ago

Thu, Jan 22, 2004 8:40 AM

Have you checked the batterey, and the connections?

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We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

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- CWatters
  
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posted
20 years ago

Thu, Jan 22, 2004 4:36 PM

I was thinking the same. It sounds like the battery may have been allowed to go flat and/or perhaps it's been sitting like that for some time before delivery. Thats one of the fastest ways to kill a lead acid battery (even deep discharge batteries don't like it). Perhaps the seller just gave it a quick charge before delivery so that it appeared ok?

If it won't mess up onboard equipment....I would take the battery out and charge it then test it using some car headlamp bulbs to measure it's capacity.

The best way to store a lead acid battery is connected to a float charger all the time. A float charger keeps the battery at just under 100% fully charged but not so full that "boiling" occurs (eg so it doesn't dry out).