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stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

I have a two year old Bosch Factory Rebuilt Alternator. Recently I noticed the charge light on very, very, very dim, under load (head lights on, etc.) During day it is not noticeable at all, and at night, is is barely perceptible, and only with at least the headlight lights on load-wise. I replaced my battery yesterday, out of caution, as it was four years old, and I had put some strains on it over the years, and it sometimes sits for long periods. While at the auto store I had them do a charging system check.

Under no load the the output was 13.64 volts, and under load it was 13.0 volts, and the electronic tester passed the system. I believe something like 13.6 is OK for our cars, but have also seen some stuff about 14.2 etc.

Does anyone have any off the top of their head recollection of where our systems should be, or the range? Mine is a 81 931 with Bosch alternator. I believe I had upgraded to the 115X 90 amp rather than replace the 109x 75 amp standard.
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"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

Ozzie · Posted: Tue Sep 13, 2011 10:39 pm Post subject:

sounds normal to me
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

CalGuy · Joined: 17 Oct 2009 Posts: 62 Location: Woodside, CA

+1

However, do make sure you're grounds are in good shape. I believe there is a ground from the back of the alternator to the engine block.
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-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Thanks. Appreciate the confirmation it is within range.

I might order a second ground strap just as a precaution. Does anyone know of a source of one about the same scale as the factory alternator strap...would rather not have to adapt one of the full scale versions like the one going from the engine to the chassis.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Took both the 941 and the 937 out to a PCA event last night (the Blonde drove one of 'em). Both my cars are fully charging under full load as confirmed with multi-meter (one with stock Bosch unit, the other with upgraded 150A unit). Both cars exhibit the very faint glowing you describe...pretty similar between the two...
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erstwhile owner of just about every 924 variant ever made

Paul · Posted: Sat Sep 17, 2011 11:32 am Post subject:

This thread would be more useful with pictures and a brand/model number....
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Thanks for the confirmation that a faint glowing can be seen on both of the two you described. Makes me feel much better!

Curious as to your voltages.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Paul · Posted: Sat Sep 17, 2011 11:15 pm Post subject:

I don't recall the 77 924 that I bought new ever having this problem for the couple of years I owned it.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Paul · Posted: Sat Sep 17, 2011 11:19 pm Post subject:

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Sounds just like mine. My guess is this is normal and not even a result of additional resistance in old wiring. From what I read it occurs when there is a voltage difference between the battery and alternator, either direction. So there may be some very slight delta that causes this normally. BTW, just as a reminder, our Bosch alternators have the exciter circuit, where they won't work unless the warning bulb is installed (and the warning bulb needs to be the correct wattage.)
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.