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#592746 - Sun Nov 15 2009 04:26 PM How do I test my 6 volt generator?
Spencer Rogers Offline
Wrench Fetcher
Registered: Fri Nov 04 2005 12:00 PM
Posts: 58
Loc: Bath, PA
I have a 1949 3600 with the original motor and electrical system. I am trying to figure out the best way to verify if my system is charging the battery? I am sure it is something simple, but I am not sure how to do that.

Can someone kindly reply with the steps to rule out a bad generator?
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#592747 - Sun Nov 15 2009 04:31 PM Re: How do I test my 6 volt generator? [Re: Spencer Rogers]
FriedGreenTmater Offline
Shop Shark
Registered: Fri Jun 05 2009 10:27 AM
Posts: 3256
Loc: colorado
The proper way is to check it with a volt meter at the battery with the vehicle running. If you don't have one you can disconnect the negative battery terminal while the truck is running, if it dies you are not charging, if it stays running you are. Do not disconnect the positive, more potential for unwanted sparks.
_________________________
Fried Green T'mater (Vern)
1953 Chevrolet 3600
In the Stovebolt Gallery
More pix on Photobucket
Caution: Political Statement

Man who runs in front of car gets tired, man who runs behind car gets exhausted.
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#592749 - Sun Nov 15 2009 04:35 PM Re: How do I test my 6 volt generator? [Re: Spencer Rogers]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 12503
Loc: Dellrose, TN
First, momentarily attach a jumper wire from the BAT terminal of the regulator to the ARM terminal, for no more than a second or two. This "polarizes" the generator, establishing "residual magnetism" in it. With all the wires removed from the generator, there should be at least 1/2 volt present at the ARM terminal of the generator with the engine running. If this voltage is not present after polarizing, don't bother with any other tests- - - - -you've got a bad generator. If the residual voltage is there, reconnect the wiring, and run the engine with a jumper wire connected between the FLD terminal of the generator and ground. The voltage at the ARM terminal should increase rapidly as you rev up the engine. Do not allow it to go above 8 volts or so. If it will do that, you've got a generator that's capable of charging the battery. If it's not charging, the trouble is in the regulator or the wiring. Do the same series of tests- - - -ground the Field wire and measure voltage at the ARM wire of the regulator to check the condition of the wiring.
Jerry
_________________________
"We have met the enemy, and he is us!"- - - -Pogo
I'm a dyslexic agnostic with insomnia- - -I stay up all night wondering if there's a DOG!

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#592750 - Sun Nov 15 2009 04:42 PM Re: How do I test my 6 volt generator? [Re: Hotrod Lincoln]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 12503
Loc: Dellrose, TN
PLEASE don't disconnect battery terminals with the engine running- - - - -you can do major damage to anything that's voltage-sensitive when the generator voltage spikes to 50 volts or more momentarily. I've seen that on an oscilloscope dozens of times. Definitely don't do that on a vehicle with an alternator, and NEVER do it on one with a computer!
Jerry
_________________________
"We have met the enemy, and he is us!"- - - -Pogo
I'm a dyslexic agnostic with insomnia- - -I stay up all night wondering if there's a DOG!

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#592753 - Sun Nov 15 2009 04:50 PM Re: How do I test my 6 volt generator? [Re: Hotrod Lincoln]
FriedGreenTmater Offline
Shop Shark
Registered: Fri Jun 05 2009 10:27 AM
Posts: 3256
Loc: colorado
Hotrod is correct according to the books. However I have done this to just about every vehicle I have owned without mishap except for the once I pulled the positive cable instead of the negative. Turns out my alternator was over charging and the battery was letting out gas, nobody was hurt but it was scary. Probably might have happened with either cable. Definitely a shade tree maneuver, but it gives you an answer pretty quick.
_________________________
Fried Green T'mater (Vern)
1953 Chevrolet 3600
In the Stovebolt Gallery
More pix on Photobucket
Caution: Political Statement

Man who runs in front of car gets tired, man who runs behind car gets exhausted.
Top
#592773 - Sun Nov 15 2009 05:47 PM Re: How do I test my 6 volt generator? [Re: FriedGreenTmater]
Spencer Rogers Offline
Wrench Fetcher
Registered: Fri Nov 04 2005 12:00 PM
Posts: 58
Loc: Bath, PA
I have a volt meter and can certainly check it that way, but what am I looking for on the meter? More voltage than the battery has by itself?
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#592807 - Sun Nov 15 2009 08:05 PM Re: How do I test my 6 volt generator? [Re: Spencer Rogers]
truckernix Offline
Registered: Sun Mar 24 2002 12:00 PM
Posts: 8537
Loc: Bracebridge Ontario Canada
When the motor is running well above idle, you should see about 7.2 v or so.
_________________________
1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!
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#592829 - Sun Nov 15 2009 09:08 PM Re: How do I test my 6 volt generator? [Re: Spencer Rogers]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 12503
Loc: Dellrose, TN
If the battery is very low on charge, the charging voltage at fast idle should be about 6.5 to 6.8 volts. As the battery charges up, the current flow should decrease (ammeter closer to center) and the voltage should go up. With a fully-charged battery, the charge current should be 5 to 8 amps, and the voltage should be around 7.2 to 7.5 volts volts.
Jerry
_________________________
"We have met the enemy, and he is us!"- - - -Pogo
I'm a dyslexic agnostic with insomnia- - -I stay up all night wondering if there's a DOG!

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#593490 - Wed Nov 18 2009 07:37 AM Re: How do I test my 6 volt generator? [Re: truckernix]
Spencer Rogers Offline
Wrench Fetcher
Registered: Fri Nov 04 2005 12:00 PM
Posts: 58
Loc: Bath, PA
the challenge I have with this is that I will not get that reading. I use an 8 Volt battery, so the voltage is more than that when the battery is charged. Is there another location where I can check the output of the generator to see if I am getting that voltage?
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#593494 - Wed Nov 18 2009 07:55 AM Re: How do I test my 6 volt generator? [Re: Spencer Rogers]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 12503
Loc: Dellrose, TN
Dump the 8 volt, or find a pro who can adjust the regulator to charge it. Then buy a BUNCH of light bulbs, particularly headlights. With the regulator set properly, you'll fry lights at a record rate. An 8 volt battery is a solution to a nonexistent problem. Your voltage regulator setting needs to be 9 volts to keep an 8V battery charged.
Jerry

_________________________
"We have met the enemy, and he is us!"- - - -Pogo
I'm a dyslexic agnostic with insomnia- - -I stay up all night wondering if there's a DOG!

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