Motorsports Village
http://motorsportsvillage.com/forum/

backfeeding alternator
http://motorsportsvillage.com/forum/viewtopic.php?f=7&t=7363
Page 1 of 1

Author:  zephyrc [ Sun Jun 27, 2010 6:57 am ]
Post subject:  backfeeding alternator

i found today that if i switch the motor off it continues to run until it runs out of fuel,, is it possible that the alternator is backfeeding the ignition system.. if i disconnect the alt light wire at the alternator motor stops as soon as i turn it off, also if i remove the bulb it stops when turned off.. when i turn it off the warning light comes on and stays on until motor runs out off fuel..alternator is a powermaster 7294

Author:  Ken0069 [ Sun Jun 27, 2010 8:08 am ]
Post subject:  Re: backfeeding alternator

You need to add a diode to your dash light/exciter circuit to prevent current feedback to the MSD. The user manual from MSD has a section in it to deal with this issue.

Author:  rick360 [ Sun Jun 27, 2010 8:59 am ]
Post subject:  Re: backfeeding alternator

zephyrc wrote:
i found today that if i switch the motor off it continues to run until it runs out of fuel,, is it possible that the alternator is backfeeding the ignition system.. if i disconnect the alt light wire at the alternator motor stops as soon as i turn it off, also if i remove the bulb it stops when turned off.. when i turn it off the warning light comes on and stays on until motor runs out off fuel..alternator is a powermaster 7294


When you turn off what switch? Main battery disconnect or the ignition switch?

Did you change something or when/how did this happen.

Rick

Author:  zephyrc [ Sun Jun 27, 2010 11:23 am ]
Post subject:  Re: backfeeding alternator

rick,, it is happening when i turn of the ignition switch,,, my ign live is fed from a fuse board to all ign live parts including the alt light and oil pressure light.. its been that way for 3 years or more, but only now has it started back feeding.. have i wired the car incorrectly or is the alternator faulty

Author:  zephyrc [ Sun Jun 27, 2010 11:52 am ]
Post subject:  Re: backfeeding alternator

alternator has 3 wire connectios,,. main power feed to battery,,, alternator warning light and another terminal which i am told is to sense battery voltage

Author:  rick360 [ Sun Jun 27, 2010 1:34 pm ]
Post subject:  Re: backfeeding alternator

It's strange that it did work and doesn't now, but I'd look into the MSD info like Ken suggested. You are definitely getting power back to your ignition from your alternator. A diode should prevent that. On 3-wire alts I always wired them as 2-wire using only the main large wire and a single wire from ignition with a diode between the terminals. I remember when the diode was backward the car wouldn't turn off.

Rick

Author:  zephyrc [ Sun Jun 27, 2010 5:08 pm ]
Post subject:  Re: backfeeding alternator

have ordered the diodes, will be a couple of days i guess, will fit one and let you know.. is this a fault in the alternator that has arisen..

Author:  Ken0069 [ Sun Jun 27, 2010 5:13 pm ]
Post subject:  Re: backfeeding alternator

zephyrc wrote:
have ordered the diodes, will be a couple of days i guess, will fit one and let you know.. is this a fault in the alternator that has arisen..


Can't answer that but I run a 3 wire on both my cars. One has a 7AL and the other has a Digital 7 and both require that diode before they will shut off by the switch.

Author:  phillygoat [ Fri Jul 08, 2011 12:00 am ]
Post subject:  Re: backfeeding alternator

Just curious if the diode took care of it or was it something else?

PHILLYGOAT

Author:  morpheus [ Fri Jul 08, 2011 5:22 pm ]
Post subject:  Re: backfeeding alternator

I use a separate 150 amp circuit breaker in the feed line to the alternator. One click shuts the entire car down... no worries about something left on and draining battery dead.

Paid $15.00 for it, solid piece of equipment, gave me a 10% online order discount, the ride to NJ from Cali was $6.80.

Quality Power Auto, Inc., in Yucaipa, Ca. 92399.... 909-794-1600. Qualitypower@aol.com

CB-150 Circuit breaker-150 amp... was called a Scorpion IIRC.

Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/