diode on the alternator - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > diode on the alternator

Rough Country Jeep Suspension Deals at Rockridge 4WD!Engo winches available at www.rockridge4wd.com! Free shippRoad Race Motorsports Stage 2 Power Pack

Reply
Unread 10-07-2009, 06:13 AM   #1
Reverb
Registered User
1988 YJ Wrangler 
 
Join Date: Dec 2008
Location: NY
Posts: 600
diode on the alternator

Hi all,
my Yj won't turn off after it's been running. I've put a switch inline to the power for the distributor/fuel pump so i can turn it off.
I've read that it's a common problem and i need to put a diode inline with the alternator.
Anyone know what size diode and where on the alternator??

Reverb is offline   Reply With Quote Quick reply to this message
Unread 10-07-2009, 06:24 AM   #2
Alfons
Registered User
1992 YJ Wrangler 
 
Join Date: Jul 2005
Location: Ontario, Canada
Posts: 2,218
Quote:
Originally Posted by Reverb View Post
Hi all,
my Yj won't turn off after it's been running. I've put a switch inline to the power for the distributor/fuel pump so i can turn it off.
I've read that it's a common problem and i need to put a diode inline with the alternator.
Anyone know what size diode and where on the alternator??
The first thing I'd do would be to make sure the key switch was working - it it "cuts" the power, the engine should stop. A lot of things need a good steady source of DC power to keep the engine running (including the computer).
Alfons is offline   Reply With Quote Quick reply to this message
Unread 10-07-2009, 06:37 AM   #3
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,408
Pull the asd relay and see if power drops. I just spent a week with Rebuild rookie troubleshooting the same type of problem. The question is wether power is going to the system through the relay or after the relay. Disconnecting the alternator will tell you if you need the diode or not. The diode stops the alternator field from back feeding. Do both and post back
Que89YJ is online now   Reply With Quote Quick reply to this message
Unread 10-07-2009, 07:01 AM   #4
Reverb
Registered User
1988 YJ Wrangler 
 
Join Date: Dec 2008
Location: NY
Posts: 600
I'll give it a shot. Do I have an ASD relay on my 88 4.2?
Reverb is offline   Reply With Quote Quick reply to this message
Unread 10-07-2009, 07:33 AM   #5
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,408
I didnt see that. Are you nuttered? Do the alternator first.
Que89YJ is online now   Reply With Quote Quick reply to this message
Unread 10-07-2009, 08:04 AM   #6
Fernando
Registered User
1987 YJ Wrangler 
 
Join Date: Jul 2005
Location: San José, Costa Rica
Posts: 1,303
Hello

If you have a 4.2 your fuel pump is mechanical, I do not know what you mean by cutting power to the distributor, I guess you have tapped on the line that provides power to the coil, the distributor itself has no power, or maybe you interrupted the connection between the distributor and the ignition module.

You need to install this part

Radio Shack part number 276-1103.

There is a brown wire coming off the alternator, this is the battery charge wire, you need to install the diode to prevent the current from flowing back from the battery to the alternator, diodes have a "side" to them so make sure you install it the right way, you can test this with a multimeter and I know there are marks on each side but can't remember now what they look like, just use the leads of the multimeter to check for continuity, one on each side, when you get a good reading you know you have identified the flow direction.

I did this on my YJ when I installed my MSD ignition box, I do not know why a stock YJ would have this problem, the MSD runs on so little current that a few volts coming back from the battery to the alternator were enough to keep it running.

Use proper soldering when attaching the diode and when you are done cover everything in shrink wrap.

If you need help I can take a picture of the wire but later today when I get off work

Good luck!
__________________

Quote:
Originally Posted by JeepHammer
I don't mind writing for Fernando because he reads, and re-reads EVERY WORD!... Good to write for someone that actually READS the answer, and takes time to UNDERSTAND what comes back for an answer!
-------------------------------
Fernando is offline   Reply With Quote Quick reply to this message
Unread 10-07-2009, 10:07 AM   #7
Reverb
Registered User
1988 YJ Wrangler 
 
Join Date: Dec 2008
Location: NY
Posts: 600
Sorry I should have updated my profile - Currently running a HEI distributor and an electric fuel pump. I will get that diode and install it - I kinda like the kill switch I have in there so will probably leave that as an anti theft device.

thanks all for the help.

EDIT: 1A rating is enough for the diode?
Reverb is offline   Reply With Quote Quick reply to this message
Unread 10-07-2009, 10:12 AM   #8
Fernando
Registered User
1987 YJ Wrangler 
 
Join Date: Jul 2005
Location: San José, Costa Rica
Posts: 1,303
Quote:
Originally Posted by Reverb View Post
Sorry I should have updated my profile - Currently running a HEI distributor and an electric fuel pump. I will get that diode and install it - I kinda like the kill switch I have in there so will probably leave that as an anti theft device.

thanks all for the help.

EDIT: 1A rating is enough for the diode?
This is the part number recommended by MSD, should be fine, mine has worked flawlessly
__________________

Quote:
Originally Posted by JeepHammer
I don't mind writing for Fernando because he reads, and re-reads EVERY WORD!... Good to write for someone that actually READS the answer, and takes time to UNDERSTAND what comes back for an answer!
-------------------------------
Fernando is offline   Reply With Quote Quick reply to this message
Unread 08-24-2013, 03:20 PM   #9
superj
Registered User
1987 YJ Wrangler 
 
Join Date: Mar 2008
Location: corpus christi, texas
Posts: 6,594
This diode fix works great on the 76 cj5 we bought two weeks ago. I know this thread is from many moons ago, the info is still relevant as the diode part number is the one I just bought and installed and now the cj turns off properly
__________________
Slow ride, take it easy
superj is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
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.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.