Alternator external diode
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=9962
Printed Date: May-12-2024 at 7:15am
Topic: Alternator external diode
Posted By: Greg_SA
Subject: Alternator external diode
Date Posted: March-28-2008 at 6:01am
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Hi,
I was looking at the wiring on my alternator (on a '89 SN2001)... there is an external diode in-line with one of the wires... any idea what it is? I'm not sure which wire it is, but I'll check next time. I'm not sure if it is the exciter or the output... Anyone noticed this on their alternator? Cheers Greg |
Replies:
Posted By: boat dr
Date Posted: March-28-2008 at 2:24pm
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The diode is in place to prevent a back feed from your alternator to the ignition. Remove this device and the motor will not DIE when the ignition switch is turned to OFF.....
If the diode is turned around or reversed the alternator will not energize.......Boat dr ------------- boat dr /diaries/details.asp?ID=4631 - 1949 Dart /diaries/details.asp?ID=1533 - 1964 American Skier |
Posted By: Greg_SA
Date Posted: March-28-2008 at 6:42pm
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Okay, thanks for the info... ;-)
It is probably in line with the exciter supply then - allowing current to flow from the ignition to the exciter of the alternator, but not the other way round. Is this diode normally mounted on the alternator, or just wired in-line with the wiring harness? Mine is just wired in-line with electrical terminals, which doesn't look very OEM.. |
Posted By: Greg_SA
Date Posted: April-01-2008 at 3:30pm
| Can anyone confirm that the diode is just "in-line" with electrical terminals? |
Posted By: nuttyskier2002
Date Posted: April-05-2008 at 1:55am
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Greg the diode does not need to be mounted to anything. Just make sure the connections/leads on the diode are insulated to that you don't have a shorting problem. Heat shrink is good. I'm assuming this is an aftermarket upgrade (alternator),... is that right? The biggest reason to mount a diode would be for heat dissipation. This circuit doesn't flow enough current for that to be an issue. ------------- 95 Malibu Echelon w/Mercruiser 350 Magnum Skier Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
Posted By: Greg_SA
Date Posted: April-05-2008 at 12:22pm
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nuttyskier2002 - Thanks for the info...
The diode was poorly installed, and I have soldered it in line and used heat shrink already. What I'm really asking is if this is how the boats came from the factory... with an external diode? Or do they have a diode inside the alternator? I am not sure if my alternator is original or not - it is a Presolite. I think the previous owner had it re-wound and reconditioned. Thanks, Greg |
Posted By: 79nautique
Date Posted: April-05-2008 at 12:34pm
explain that to me, I don't see how it could have any heat dissipating property's, know it was never used that way on any Delcotron unit. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
nuttyskier2002 wrote:Posted By: boat dr
Date Posted: April-05-2008 at 12:38pm
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Greg, get out of the problem and into the solution. The diode was installed after the fact, possibly the wrong alt.After run from a back feed would allow the engine to run after the key was turned off.
Now is a good time to install a one wire GM 10 SI. Different systems use different wiring configurations,one is not right or wrong .............Boat dr ------------- boat dr /diaries/details.asp?ID=4631 - 1949 Dart /diaries/details.asp?ID=1533 - 1964 American Skier |
Posted By: 8122pbrainard
Date Posted: April-05-2008 at 1:36pm
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Greg, Don't worry about the looks - Under the dash is even worse!! I remember Woody stating that the OMC's came from the factory with the diode in line. They dipped the whole thing in red potting compound. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: nuttyskier2002
Date Posted: April-05-2008 at 2:06pm
Some diodes have heat dissipation properties and some don't. It depends on the style. I haven't seen the style of diode used in his application. The one I used on mine is the type that would normally be mounted in a heat sink. I was merely stating that in his case that wasn't a factor. I totally agree that his alternator wiring is not factory original. ------------- 95 Malibu Echelon w/Mercruiser 350 Magnum Skier Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
Posted By: Greg_SA
Date Posted: April-06-2008 at 8:01am
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Thanks for all the info... :D
The setup works fine at the moment, so I'm not going to replace anything. I just didn't like the way the diode was installed inline, so I wanted to make that more secure. It seems like most OEM setups don't have the diode inline with the wiring, so I assume they are fitted inside or onto the back of the alternator. I looked at the alternator on Skidim, and it looks like it has a diode mounted to the back. It has an extra electrical post though which I don't think mine has :) Oh well, I'll leave it as it is for now... thanks again for all the info! http://www.skidim.com/images/RA097006.jpg 
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