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Thread: Alternator woes

  1. #81
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    Re: Alternator woes

    so basically just perform these tests (?) => https://www.wikihow.com/Check-an-Alternator

    If it DOESN'T pass the voltage tests how can I be sure it is the alternator and not the wiring harness/fusible link/other crispy wiring issues that may be feeding the alternator?

    I am also getting a whine from the engine compartment (hard to pinpoint) which combined with the Christmas lights point pretty firmly in the direction of a new alternator.

    I just don't want to jump to that conclusion without ruling out other components like the wiring harness etc.
    Last edited by cpginkpt; 06-02-2019 at 06:03 PM.

  2. #82
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    Re: Alternator woes

    We cannot tell you what direction to go until we know battery voltage. If you have a volt meter, get a reading from your battery while the van is running. For most accurate results, take the van on a 15 minute drive and get the volt reading while somebody is holding the vans throttle at ~ 2000 RPMs.

  3. #83
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    Re: Alternator woes

    Cold battery => 12.65
    Start van, rev to 2k on tach => 14.68

    15 minute drive
    rev to 2K on tach => 14.88

    turn on fan and AC, rpms drop from 1100 to 700 + engine shudder, volts drop to 13.2 and then slowly climb back up to 13.8 after 30 seconds. RPM still low with engine shudder.

    Turn off fan and AC, volts return to 14.7 with no engine shudder and 1100 on tach

    tune radio station to low AM frequency with static and rev engine. Upon rev the volume of static increases.

    turn off engine => 13.01

  4. #84
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    Re: Alternator woes

    Although still below 15V, this is unusually high. I suspect an open in the battery sense circuit (would cause your alternator's internal regulator to go to max output). Staying below 15V could be due to a strong battery (ballast) or perhaps it's just the max output of your particular alternator. Most likely failure would be your FL 0.5G fusible link (little yellow plastic part in your battery compartment). It's talked about here in the Fusible Link Thread. Tim

    Quote Originally Posted by timsrv View Post
    Here is the next most problematic fusible link. The FL 0.5G fusible link is the yellow connector going to the positive battery post inside your battery box. It is rated at 0.5G (based on wire gauge, I'm guessing about 20A). This protects the alternator sense circuit that links the battery positive to the "S" terminal of the voltage regulator (built into your alternator). If this link is bad or disconnected, the end result is solid "Christmas lights" on your instrument panel and a "full field" condition in your alternator. Full field is when the regulator tells the alternator to go to maximum output all the time and can be dangerous. A short trip probably wouldn't cause any problems, but long term use could cause multiple electrical problems (due to over voltage) and worse case scenario could end with a thermal runaway condition occurring with your battery. Thermal runaways are scary and dangerous. The result is usually a pile of molten lead, plastic and battery acid all over the place. Thermal runaways have also been known to start fires, so don't push your luck with a bad or failing FL 0.5G link. Here is a what a typical 20 something year old one looks like:


    Although slightly more protected than the main fusible link, this link is still in a harsh environment and after 20 years or so will probably need some attention. I haven't checked to see if these are still available through Toyota, but really didn't see the need for genuine Toyota here. If Toyota still has these, they will no doubt want more $$$ for them than what they are worth. I have found a good substitute for these through Summit Racing for $2.95. These PICO fuse holders are water tight and are rated at 30A. Since this is a "sense" circuit, there would normally not be any current here, so I am going to recommend using a 15A ATC fuse. Here are a couple of pictures:






  5. #85
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    Re: Alternator woes

    ah, good (or not)!....based on your first pic and what I see under the battery compartment I would say mine is snapped right off (below). I see a wire to the right and nothing connected to the fusable link so assume these should be connected.

    So I will just order the part you recommended, cut out the old one and sotter the new one in place. Doesn't matter which wire goes where I assume (?)
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    Re: Alternator woes

    Yep, that's the rascal. Looks like corrosion infiltrated into the wire insulation. Cut that wire back until you see clean copper, then splice in an in-line fuse holder. Makes no difference what wire goes where. You could technically just cut the old one out and connect the 2 wires together, but having fuse protection is better/safer. Any in-line fuse holder would work (available almost anywhere), I just like the one posted above due to it's water tight cover. After you get the sense circuit back together please update with new battery voltages and report back on your "Christmas dash" issue. Tim

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    Re: Alternator woes

    on it. Will report back. Thanks as always Tim!

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    Re: Alternator woes

    Christmas is cancelled!

    It's definitely going to take me a while to get used to NOT seeing lights in the dash - I keep looking down and thinking something is wrong - ha!

    Got the weatherproof fusible link (3.99 at local O'Reilleys), I threw in a 15 amp fuse until I can get back to Napa to grab a 30 - seems to be holding for now.

    Voltmeter still reads high but maybe that is my battery size as Tim suggested

    engine off - 12.90
    2K rev after a 10 minute drive 14.38

    AC on will still drop the tach from 8 to 5/6 and add some engine shake plus lower the voltage to 14.1 - but I think that may be the little dial behind the glovebox to adjust idle with AC on. Project for another day.

    Thank you Tim!
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    Re: Alternator woes

    Leave the 15A fuse in there (in case of a short, the wire in the sense circuit can't hold 30A). Since this is a sense circuit, there is no current draw, but you want the fuse to blow if that wire ever gets shorted. The wire in that circuit will max out at around 15 - 20A, so 15A is a good size fuse for this application. Tim

    PS: Voltage is still a tiny bit on the high side, but within limits.

  10. #90
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    Re: Alternator woes

    Hey guys,

    So I've been looking around the forum for a few days to find a similar problem to mine but I can't really find any and I didn't want to start a new thread since I am assuming it's an alternator or electrical problem.

    I have an automatic 1984 Toyota Van.

    I have been having troubles with what I am assuming is the alternator. I can drive the van fine, but if I turn the headlights on or the AC she'll run a little rougher. Also if I am sitting in park and rev the engine with AC on or Headlights she'll almost die or acutally die when her RPMs come back down. This happened yesterday in a big intersection, had the AC on and started to go but had to brake due to an ambulance coming through and she just died when the RPMs came back down. I turned the AC off and fired her back up and drove her home.

    Additional note: I do not have the Christmas tree when the van is in drive or when the van is on.

    I took some voltometer readings today. (All the readings are when connected to the battery)

    Cold Battery: 12.6v
    Started van: 14.6v
    Warmed up van: 14.6v-14.5v
    AC turned on: 14.4v right away, AC was on full blast and within two minutes the battery dropped to 12.8v
    Revved the motor up and let off gas all the way and she died all the way. Turned AC off and restarted it and the battery was at 14.4v upon restart and slowly came back up to 14.6v

    Any help is much appreciated

    Michael

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    Re: Alternator woes

    stolz, I don't think that has anything to do with the alternator (your voltages seem fine). Running rough could be lots of things, but if it stalls when running the AC I'd adjust your Idle-Up Diaphragm. The earlier ones have an adjustment to make the engine idle-up when the AC is on. Here's a thread where this is discussed:

    https://www.toyotavantech.com/forum/...tached-diagram

  12. #92
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    Re: Alternator woes

    Does anyone have a diagram to connect the alternator of a 1984 Van? It has an alternator adapted from chevrolet and I want to put the original.

  13. #93
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    Re: Alternator woes

    Quote Originally Posted by GonzaloM View Post
    Does anyone have a diagram to connect the alternator of a 1984 Van? It has an alternator adapted from chevrolet and I want to put the original.
    I posted that information on post #24 (this thread). I don't know which Chevy alternator you have, but my guess is it's better than a Denso alternator. If that one is having an issue I think you'd be better off repairing that one or replacing with a similar model. After all, the conversion has already been completed. Tim

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