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Registered User
Join Date: Jul 2016
Posts: 1
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Diode on blue wire to generator warning light
I'm having some trouble with the generator warning light staying on (1976 930). Looking at the current flow diagrams I'm wondering if this can be related to the diode between the blue wire and circuit 90.
What is the function of this diode? Last edited by bds_; 07-15-2016 at 06:28 AM.. |
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07-15-2016, 06:24 AM
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Moderator
Join Date: Aug 2002
Location: OverlandPark KS (Kansas City)
Posts: 526
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Yep, that will cause it. It stops the field wire from getting backfed. If it goes bad then the system will not ignite the field wire properly. It is on the harness behind the gauges. You can test it with a continuity tester. It should only allow flow one way. Should be in a clear plastic sleeve. I wouldn't order it through Porsche. Its a common 1/4 watt diode you should be able to get at a local electrical supply store.
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Stephen 94 3.6Turbo 6-speed AWD |
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07-15-2016, 08:45 AM
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Registered
Join Date: May 2005
Location: Loxahatchee, florida
Posts: 2,894
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it's no longer available either from porsche.
Took me about 6 months to find a stock replacement. in the meatime i just bypassed it and everything worked fine. If it's open your battery will not charge correctly.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's. 2019 Silverado 6.2L |
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07-18-2016, 09:19 AM
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Registered
Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
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my crappy 76 diagram does not show the diode in the charging circuit for all practical purposes.
my 78 shows it in series with the idiot light. it is probably there for isolation so current only flows in one direction. if this is the case, if diode is shorted, the charging may or may not work. the light will come on with key on and engine off. no mater why it is there, if it is open, it will not charge and the light will never come. for some reason I am thinking I read that it could be there for the .7v voltage drop but I cant find that. what is the charging system doing the diode can be checked with a MM
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07-18-2016, 10:58 AM
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Registered
Join Date: May 2005
Location: Loxahatchee, florida
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if it's shorted it will still charge if it's open then it will not charge correctly. if it's shorted the light comes on then goes off if i remember correctly
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's. 2019 Silverado 6.2L |
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07-18-2016, 11:11 AM
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