The Ford Barn

jaguar6165 · 09-27-2010, 11:44 PM

I am having trouble with my alternator charging my battery after a couple of weeks the battery needs to be charged I know this has been brought up but i wanted to make sure my alternator is hooked up correctly.

Tom Wesenberg · 09-27-2010, 11:50 PM

Are you running 6 volt + ground?

Connect a volt meter to ground and the alternator output and take a reading with the engine off. Then start the engine and take a reading again. Then turn the lights on and take a third reading.

Let us know what the three readings are.

MikeK · 09-28-2010, 08:51 AM

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All single wire alternators have a parasitic drain. With the engine and key off disconnect the wire from the alt. output to the starter battery terminal. Use a meter to measure DC ma (milliamps) between the alternator and the wire you disconnected. This is the parasitic drain, often 30 milliamps or more (0.030 amps). Multiply that by hours and you will find how many ampere-hours you are draining over a period of time. Example:: Measured: 43 ma; Time: 1 week- 0.043 X 168 hours = 7.2 amp-hours. If your battery was rated 20 amp-hours, that would be a bit over 1/3 down in a week.

Three possible fixes: 1) Install & use a battery disconnect in the battery ground lead. 2) Use a correct 3 wire alternator hookup. 3) Drive the car more often!

09-27-2010, 11:44 PM	#1
jaguar6165 Senior Member Join Date: May 2010 Location: Casselberry, FL Posts: 188	Charging problems I am having trouble with my alternator charging my battery after a couple of weeks the battery needs to be charged I know this has been brought up but i wanted to make sure my alternator is hooked up correctly.

09-27-2010, 11:50 PM	#2
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Charging problems Are you running 6 volt + ground? Connect a volt meter to ground and the alternator output and take a reading with the engine off. Then start the engine and take a reading again. Then turn the lights on and take a third reading. Let us know what the three readings are.

09-28-2010, 08:51 AM	#3
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Charging problems Sponsored Links (Register now to hide all advertisements) All single wire alternators have a parasitic drain. With the engine and key off disconnect the wire from the alt. output to the starter battery terminal. Use a meter to measure DC ma (milliamps) between the alternator and the wire you disconnected. This is the parasitic drain, often 30 milliamps or more (0.030 amps). Multiply that by hours and you will find how many ampere-hours you are draining over a period of time. Example:: Measured: 43 ma; Time: 1 week- 0.043 X 168 hours = 7.2 amp-hours. If your battery was rated 20 amp-hours, that would be a bit over 1/3 down in a week. Three possible fixes: 1) Install & use a battery disconnect in the battery ground lead. 2) Use a correct 3 wire alternator hookup. 3) Drive the car more often!