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Registered
Join Date: Oct 2017
Location: houston, texas with Enzo SPCA # 8995
Posts: 445
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Correct alternator for add on A/C?
The car is a '69E with a '73T motor (MFI). I don't know specifically what alternator it has, but when I added the A/C unit the shop owner (knowledgeable guy, for sure) said my alternator was fine and I didn't need a bigger one. (which he could easily have sold me without any questions). Since the install in April, the car has had 2 episodes of not starting, requiring a jump. In both cases I'd run the AC that day.
I bought the car at RM auctions, so don't know the history of the batteries in the car. I asked a different tech to swap the 75amp alternator i have in my '74 Carrera (no AC) but he said it wouldn't fit. Now maybe, the batteries are just toast and new ones are all i need, but if I need a bigger alternator, I wanna do it. If so, which one would I get that will fit? thanx steve
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Steve Meltzer '69 911E/bastard |
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08-12-2019, 06:17 PM
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ROW '78 911 Targa
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Test the batteries at a shop first.
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Dennis Euro 1978 SC Targa, SSI's, Dansk 2/1, PMO ITBs, Electric A/C Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds. |
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08-12-2019, 06:33 PM
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thanx so much, that's on my agenda, as well as an alternator test. thanx s
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Steve Meltzer '69 911E/bastard |
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08-12-2019, 09:07 PM
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which reminds me...this my first experience with 2 12V batteries in parallel. when you test the alternator (in the car) which battery do you test, or both? and how 'bout looking for a parasitic current leak? thanx. s
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Steve Meltzer '69 911E/bastard |
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08-12-2019, 09:09 PM
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ROW '78 911 Targa
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Test both independently.
Do you suspect a parasitic draw? Using just one battery connected, put an ammeter in series with the ground strap and the negative terminal of the connected battery to measure any current flow. If more than just the clock, pull fuses one at a time to see which circuit it goes away on.
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Dennis Euro 1978 SC Targa, SSI's, Dansk 2/1, PMO ITBs, Electric A/C Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds. |
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08-12-2019, 09:27 PM
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Registered
Join Date: Oct 2017
Location: houston, texas with Enzo SPCA # 8995
Posts: 445
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thanx Dennis, that's how i was taught, as well. s
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Steve Meltzer '69 911E/bastard |
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08-13-2019, 05:20 AM
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Get off my lawn!
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The AC draw is not that great. If your batteries and alternator are OK, there has to be a draw from something else.
One of the many upgrades I did to my 911 is send the tachometer in and had a volt meter built right into the bottom of the tach. That way the voltage is right in my face and easy to monitor. It looks right, as if it was factory. Why Porsche did not put in a volt meter is beyond me. So like the others said, check the batteries.
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Glen 49 Year member of the Porsche Club of America 1985 911 Carrera; 2017 Macan 1986 El Camino with Fuel Injected 350 Crate Engine My Motto: I will never be too old to have a happy childhood! |
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08-13-2019, 05:38 AM
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Heinz
Carrera
