Help with coil and resister - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-03-2005, 09:41 PM
whatwouldscoobydo's Avatar
Member
 
Join Date: Dec 2004
Location: Idaho
Posts: 72
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Help with coil and resister

Put a complete wiring harness from a 75 nova in my 38 stude.The nova had a six cylinder with eletronic ignition.I have about a 74 350 with points distributor.Used the same wire going to the coil.After a few hundred miles,burnt up the wire in the distributer to the points.Replaced the wire and points,and installed a resister (from the auto parts store)in line before the coil.Had 12 volts in and about 7 volts out to the coil.Now after driving it a few times decided to check things and I have 12 volts running thru and to the coil! Any Ideas?Tom

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-03-2005, 11:45 PM
goldenrog
 
Join Date: May 2005
Location: st paul
Age: 60
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
If the points are open when you test the voltage, you will have available voltage every where in the circuit. When the points are closed and the circuit is operational, you should find the 7 or so volts you're looking for.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-04-2005, 03:53 AM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Points

Doc here,

As goldernrog said..you have to test the coil under a load..(points closed) to see the 7 volts..If the load is removed, current goes low, voltage goes high..

It is the same as putting a meter on the ground side of a light bulb, with the ground removed..you will read 12 volts at the ground through the bulb, but the light isn't lit..(no current draw) when you ground the wire to the light, the bulb lights..and is drawing max (High)current voltage goes to zero...

Recheck it with the points closed..bet you'll find it's 6 to 9 volts...

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-08-2005, 08:51 PM
whatwouldscoobydo's Avatar
Member
 
Join Date: Dec 2004
Location: Idaho
Posts: 72
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok, noticed small voltage .9 volts (with key off) on the line going to the resister.It bleeds off to 0 volts with the volt meter connected.Replaced resister with 1.81 ohm resister,this was the highest resistance they have.With truck running, I have 14.01 volts going to resister, out the other side theres 10.97 volts.Should I take the meter reading from the line between the coil and ditributer?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-09-2005, 04:25 PM
goldenrog
 
Join Date: May 2005
Location: st paul
Age: 60
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok, the small amount of voltage may be coming from the capacitor (condensor). Is the resistor you're using automotive? If it is, the voltage you have should be fine. If not automotive, hit up your parts store for a ballast resistor for an early (60's-mid 70's) Chrysler product.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-09-2005, 04:47 PM
whatwouldscoobydo's Avatar
Member
 
Join Date: Dec 2004
Location: Idaho
Posts: 72
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Yes the resistor is auto ,and I believe it is a mopar.Haven't tried this time to see what the voltage is with the motor not running but the key on.If the points are closed is this when I should see 6-7 volts?Thanks for all the help.Tom
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-09-2005, 06:18 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Ballast

Doc here,

You want to test your system this way, Set the points to "Closed", With that done, Measure the Voltage on the line coming from the Ignition primary and ignition secondary (the solenoid) or the upstream side of the ballast resistor.

It should read, 12 volts continueous...Static with the key on, or cranking..(if you crank it return it to the points closed position for further testing)

Then Check the downstream side of the coil power wire (Ballast to Coil wire) With the points closed the voltage should read between 6 to 9 volts ...

When (with the points closed) you turn the key off, it should drop to zero right off..The Closed points should pose a direct load to ground on the Capacitor/RFI filter and discharge it right away.

If you have that, you should be fine, as far as ballast, primary and secondary ignition...

If you are worried about possible harness burnout again in the future, just add an in-line fuse holder and fuse.

To figure out the proper draw of the coil, measure with an ohm meter the primary side of the coil and case ground..

The amount of resistance divided by the voltage will give you the draw..Then add a "Little" bit more on the fuse rating and make it a Slo~blow fuse...

Say if the draw is 4 amps..make it a 5 slow blow..and the reason for this is, the coil is subject to current "Spikes" as the points open and close..

The slow blow will Buffer this effect a bit..instead of poping at random (like when you don't need to lose ignition coil power..merging onto a freeway..)you can safely raise the value up to about 7 1/2 or 10 amps if you suffer random fuse blowout..but after that, it won't much protect the wires between source current and the load..and defeat the purpose of the fuse..

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-09-2005, 09:05 PM
whatwouldscoobydo's Avatar
Member
 
Join Date: Dec 2004
Location: Idaho
Posts: 72
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Checked it with the points closed,6-7 volts,but didn't check it while cranking the motor.So is the voltage of 10+ volts while the engine is running ok?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-09-2005, 09:37 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Quote:
Originally Posted by whatwouldscoobydo
Checked it with the points closed,6-7 volts,but didn't check it while cranking the motor.So is the voltage of 10+ volts while the engine is running ok?
Doc here,

Yup. The voltages rise with the aid of the alternator.

The Crank test only shows the Secondary is hooked up, and that the wire is on the right side of the resistor..since it is only momentary, (while cranking) It's not a big problem if it's on the wrong side..The primary is what counts.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ballast Resistor -yes/no?? bomo Engine 18 01-09-2007 07:12 AM
Where the resistor wire supposed to go ? Olds 69 Electrical 33 02-08-2005 01:10 AM
Rertronix Ignition Question Dave E Shank Engine 30 12-30-2004 05:41 AM
Starter wiring problem 61ChevyTruck Electrical 5 03-19-2004 01:59 PM
Mallory coil vs. MSD Blaster 2 McDeuce Electrical 10 02-29-2004 07:57 PM


All times are GMT -6. The time now is 11:55 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.