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    VWVortex


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    Thread: Post-terminal alternator options?

    1. Member pcm1978's Avatar
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      10-03-2012 06:58 PM #1
      I have a 1980 Rabbit Convertible with the stock 1.6L and no A/C. I would like to replace the 55 Amp spade-terminal alternator with a 65A or 90A alternator with post-type terminals, so that I can run a nice fat 4 gauge wire directly to the battery + cable, and so that I can run seat heaters and an amp without fear. Are there any 65A or 90A alternators with post terminals that would be a direct fit? I'm actually happy with the V-belt setup and don't want to switch to serpentine. Maybe something for a later Cabriolet w/o A/C would work?

      Also, the current alternator has been burning alternator wires. I replaced the main wires with two direct 10 gauge copper cables to the battery + terminal, and used a brand-new Lucas-type alternator plug. After having some charging issues on a recent road trip (alternator has only ever charged at 12.5V, and was dropping down to 10V at points on the journey), I pulled the alternator and noticed that the area around the terminal, including the newish connector, was all burnt again. What is that about? Is it just a crappy alternator?

      I've had horrible alternator luck with this car. After the original died at 150K, the replacements have only lasted about 10K miles each. The first was charging at 18V even after I changed the voltage regulator; the second charged fine but then ate a bearing and seized in the desert; and the third is the current one, which has always been subpar.

      And yes, I am replacing the battery (-) cable and main ground wires.

    2. Member nairmac's Avatar
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      10-03-2012 07:27 PM #2
      As far as a replacement alternator- I use the 90A post type from a Cabriolet (I just use 1992 as my reference year), requires an additional 1/4 washer behind the pulley to line it up with my non a/c, non power steering single belt setup. And ground the alternator well- I have mine grounded to the battery and the rad support- it can't hurt.
      Last edited by nairmac; 10-03-2012 at 07:36 PM.
      If you make something idiot proof, a better idiot will come along.

    3. Member rabbitnothopper's Avatar
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      10-03-2012 07:30 PM #3
      there are 3 wires

      2 red, those go to the post, use a circular crimp connection

      the blue (faded blue) goes to the D+ use a spade

    4. Member pcm1978's Avatar
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      10-03-2012 09:16 PM #4
      Quote Originally Posted by nairmac View Post
      As far as a replacement alternator- I use the 90A post type from a Cabriolet (I just use 1992 as my reference year), requires an additional 1/4 washer behind the pulley to line it up with my non a/c, non power steering single belt setup. And ground the alternator well- I have mine grounded to the battery and the rad support- it can't hurt.
      Other than shimming the pulley, is there any fitment issue with running a 90A alternator with the non-A/C bracket setup? Can I still use the stock slide bracket on the top?

      Also, if I run a new heavy gauge wire directly from the alternator to the starter terminal (where it will meet the battery + cable), are there any issues with running 90A instead of 55A or 65A? Would it fry the electrical system or sap power from the engine? I'm assuming it puts out up to 90A, but only puts out as many amps as it needs to at any given moment.

    5. Member rabbitnothopper's Avatar
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      10-03-2012 09:37 PM #5
      um...you dont run the wire from the altenator to the starter

      you run a cable from the battery to the starter

      i am not entirely positive what the different ratings for 55,65,90 amp altenators really means

      i would suspect it means Max Rated Load which means you can safely draw up to 90 amps from the altenator without failure.

      why you had an overvoltage issue (18v) would be directly caused by a faulty altenator
      why it is charging low (12.5v) is also a faulty altenator or voltage regulator

    6. Member pcm1978's Avatar
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      10-03-2012 11:19 PM #6
      Quote Originally Posted by rabbitnothopper View Post
      um...you dont run the wire from the altenator to the starter

      you run a cable from the battery to the starter
      There's already the relatively new cable from battery + to the starter. I was thinking I could run the new alternator cable to that same terminal to meet the battery + cable there, rather than running a separate, longer cable all the way to the battery. Other cars have this set-up and, from a circuit design point of view, I can't think of a reason why it shouldn't work.

    7. Member nairmac's Avatar
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      10-04-2012 03:02 AM #7
      Quote Originally Posted by pcm1978 View Post
      There's already the relatively new cable from battery + to the starter. I was thinking I could run the new alternator cable to that same terminal to meet the battery + cable there, rather than running a separate, longer cable all the way to the battery. Other cars have this set-up and, from a circuit design point of view, I can't think of a reason why it shouldn't work.
      It'll work, but it just isn't necessary. I like the idea of no possible loss of power from the alternator to the battery though so i always run it direct, with a separate wire from the battery to the starter.
      If you make something idiot proof, a better idiot will come along.

    8. Member
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      Rabbit pickup 79/80?
      10-04-2012 10:07 AM #8
      I have the Alt output wire running to the terminal on the starter solenoid as mentioned. In an electrical sense it is the same as directly to the battery and is a bit cleaner looking as it is down low and more out of sight. This was the standard manner of American vehicle wiring from the 1940s on up so is well proven by many years of use and was also used as the feed point for the electrical system on the Aircooled VWs.

      Fred

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      10-04-2012 05:44 PM #9
      Its ok to run the alternator wire to the starter B+ stud if you need to. Almost all of the newer cars were done that way. As long as the wire from the starter tot he battery is new and in good condition the resistance is negligible and you shouldnt have charging problems. If it is the original battery cable I would either replace it with a heavier gauge or go directly from the alternator to the battery.

      I would suggest this however: If you go with a 95 am alternator you should use a B+ cable with a fusible link just in case something gets shorted so you dont burn the car down. What I always used to do is strip out the alternator wire on a fullsize ford truck or van; they have a double element fusible link and ring terminal welded on and you can go directly to the battery terminal or starter stud, your choice. The you have a fuse. The other end that connects to the alternator you can just cut to length and then have an auto electric place hydro crimp an end on it for the alternator stud...

      What you are seeing with the burning on the old motorola style plugs is very common and not just on VWs; Ford used a similar spade connector for years and it does the same thing. You will be much better off with a later stud type alternator....

    10. Member pcm1978's Avatar
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      10-22-2012 02:58 PM #10
      So I finally had a chance to get back up to the cabin and visit my car, just in time to get the new alternator in the car and pull it into the garage before the first snow of the year.

      Anyway, for future reference, I picked up a 90A alternator for a later Cabriolet and it worked well. Ran a nice 6 gauge wire to the B+ terminal on the starter and now the system is charging up near 14V again.

      The 90A alternator is slightly larger in circumference as compared to my stock 55A one but it still fit in the space, and the fit and alignment for the fan and pulley were perfect. The only issue is that the later alternator has a separate, threaded hole to mount the tensioner, and it protrudes a bit so that it didn't line up with my stock tensioning arm. After pricing out different tensioning arms, I ended up using a hardware store and picking up a turnbuckle and some shims. The set up works perfectly and is so much easier to adjust. I forgot to snap pics but I'll try to remember to get some next time I have a chance.

      Also, now my horns work again. Yay. There must be some crazy resistance in the horn wiring, because they don't work off the battery (reading at 13.3V fully charged) but do work when the alternator is running. And yes, I replaced the battery to body and body to engine ground cables.

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