Re: Resistor placement

Posted by RAB on May 07, 2007 at 02:41:47 from (195.93.21.42):

In Reply to: Re: Resistor placement posted by Dale B on May 06, 2007 at 20:45:28:

Ballast resistors were put on vehicles with 12 volt electrics originally to improve starting. Full stop. No other reason. This was to utilise the stronger spark from a 12 volt battery and 6 volt coil (rather than from a 12 volt battery and 12 volt coil) when cranking due to the larger voltage drop with the more modern, smaller, less costly batteries of the day. To do this they bypassed the ballast resistor only when cranking (fed from starter solenoid). This gave a stronger spark (from higher primary current)for starting only and reverted to the normal running circuit as soon as the feed to the starter solenoid was interrupted (when engine fired up)to prevent coil overheat and rapid contact point burn. SO, the ballast resistor was fitted before the coil with a bypass link to the coil from the starter solenoid. You would not be able to bypass it if it was fitted after the coil. If you do not want the option of a stronger spark at start-up, it makes no difference where you put that item in a series circuit. The ballast resistor is there to limit the current in the circuit. It will have a potential drop accross it as the p.d. will be shared across all the components (battery, connections, resistor, coil, wires)in proportion to the resistance values in the circuit).
Hope this helps.
Regards, RAB

Replies:

• Re: Resistor placement -- Another reason Gerald J. 07:22:29 05/07/07 (0)

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]