| Alternator Overrun [message #223908] |
Sat, 28 September 2013 20:17  |
SThornbg
Messages: 127
Registered: September 2011
Karma: 0
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On the way home from Branson, cruising down I44 the chief navigator said she smelled something strange. The voltmeter showed 18 volts, but I didn't get excited as I had recently recently returned a similiar gauge for false output. Pulled on the headlights to try to absorb extra voltage if it was really there. Next was smoke from the radio and a loss of engine power and a loud bang.
We pulled to side of the road and the engine would not restart - no response from the starter. Checked the battery compartment and engine battery had smoke rolling out of both ends at the top cover joint. Cooked all of the incandesent bulbs but the LED clearance lights were fine.
We installed the battery from the toad and the coach started fine. We drove off the interstate to a safe spot to work. We found the alternator output was zero. So, off to O'Reilley's for a new battery and alternator. Got her back together and running and the only apparent damage was light bulbs, fuse for the heater/air con and a tach that doesn't work - oh, and both mufflers are a new shape with side seams slightly opened. We had the APC installed on the alternator.
The coach ran great the remaining 400 miles home.
Is the APC comprimised by doing it's job, or is it a safe reinstall? (It is back in place now)
Steve Thornburg
South Bend, IN
77 exPB, 455 "Tinker Toy"
Steve Thornburg
South Bend, IN
77 exPB 455 "Tinker Toy"
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| Re: [GMCnet] Alternator Overrun [message #223944 is a reply to message #223908] |
Sun, 29 September 2013 00:22  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Steve,
Probably the most common cause of alternator over-voltage is failure of the
isolator. When the diode to the chassis battery opens, it prevents the
voltage sense lead to the alternator from monitoring the alternator output
(less the forward voltage drop across the isolator diode). Since your
chassis battery still received the excessive voltage, one must assume the
diode did NOT open. That being the case, then the voltage sense lead
itself, including its connections, is suspect. Of course it's always
possible that it was purely an internal failure of the alternator, but I'd
sure check that feedback loop carefully.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL
www.gmcwipersetc.com
On Sat, Sep 28, 2013 at 9:17 PM, SThornbg <SThornbg@aol.com> wrote:
>
>
> On the way home from Branson, cruising down I44 the chief navigator said
> she smelled something strange. The voltmeter showed 18 volts, but I didn't
> get excited as I had recently recently returned a similiar gauge for
> false output. Pulled on the headlights to try to absorb extra voltage if
> it was really there. Next was smoke from the radio and a loss of engine
> power and a loud bang.
>
> We pulled to side of the road and the engine would not restart - no
> response from the starter. Checked the battery compartment and engine
> battery had smoke rolling out of both ends at the top cover joint. Cooked
> all of the incandesent bulbs but the LED clearance lights were fine.
>
> We installed the battery from the toad and the coach started fine. We
> drove off the interstate to a safe spot to work. We found the alternator
> output was zero. So, off to O'Reilley's for a new battery and alternator.
> Got her back together and running and the only apparent damage was light
> bulbs, fuse for the heater/air con and a tach that doesn't work - oh, and
> both mufflers are a new shape with side seams slightly opened. We had the
> APC installed on the alternator.
>
> The coach ran great the remaining 400 miles home.
>
> Is the APC comprimised by doing it's job, or is it a safe reinstall? (It
> is back in place now)
>
> Steve Thornburg
> South Bend, IN
> 77 exPB, 455 "Tinker Toy"
> --
> Steve Thornburg
> South Bend, IN
> 77 exPB 455 "Tinker Toy"
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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