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  1. #1

    Default Alternator headache

    Long story short built a 84 t bird 302. Went through 6 rebuilt alternators of diffirent brands from rock auto and none worked. Couldn’t all be bad so I re checked my wiring a dozen times and all seemed right. Now I went and bought the best new alternator they had. 3 wire setup BAT, STA, FLO connections. Worked like a champ for about a week and my battery light came right back on. Go out and check the connections and all seem good. So I hit the bat connection with a test light and it lights up. Than I hit the FLO and STA connections and nothing. So I get a new one and it arrives yesterday. Put it on and still the battery lights on. Test again and no power at the STA or FLO hookups. Powers going in but not out it seems. Anyone else have these issues. And what alternators best that I can start enjoying this car. Everything’s perfect but this. Before I send this one back to I wanna get second opinions on if we agree something inside these alts are bad. Wiring looks perfect and car runs flawless. Everything else in the car works as should. Thanks

  2. #2

    Default

    How about voltage regulator working as should? Wiring to it and it's connector integrity? What's voltage at the battery terminals with the car running?... (by the way, that's FLD for field, not FLO...)
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3

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    Yeah my bad I just noticed it was FLD. Yeah I had a spare regulator tried it and nothing. Car worked fine last week and now it’s having issues. Brand new regulator now and wiring has not changed. Voltage at the battery is 12.8 while running drops a little slowly because the alternator is clearly not chargingg

  4. #4
    FEP Power Member 4-barrel Mike's Avatar
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    What's the voltage at the running alternator?

    How much resistance in the cable running from the alternator to the starter solenoid? Resistance in the positive cable from the battery to the solenoid?

    Mike

  5. #5

    Default

    The back off the alt sees the same amount as the battery when running and same with the starter selnoid hot side. Maybe a tiny difference lowest I saw was 12.2 volts by the battery is slowly dropping voltage itself, this time the battery only had 12.4 volts. But was running it a good bit checking stuff

  6. #6

    Default

    Running voltage should be 14+ volts. Numerous alternators says it's not an alternator problem... and I'd still suspect a voltage regulator issue, or a dead/dying battery issue...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  7. #7

    Default

    I assume the voltage is low because the car has been running/started countless times without a charging system that is functioning. 6 rebuilt alts and than I got a new one and it worked flawless for a week or so. Now this one is also not working. Swapped between 3 voltage regulators now and the same thing. I’m convinced it’s the alternator. But want to know where I can get a good one at. Summit racing list a couple but wanted to see if anyone had experience with any other options.

  8. #8

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    Test the alt at a parts store. Ive had bad luck with the older 2g alts, never felt with one without the internal regulator.

    3g is a cheap, easy and fun upgrade that doesn't cost much more then a new alt to begin with. Especially if you don't mind junk yard.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  9. #9

    Default

    Quote Originally Posted by Haystack View Post
    Test the alt at a parts store. Ive had bad luck with the older 2g alts, never felt with one without the internal regulator.

    3g is a cheap, easy and fun upgrade that doesn't cost much more then a new alt to begin with. Especially if you don't mind junk yard.
    This. The 3g swap is so easy(and cheap if JY sourced) it's not worth messing around with the 2g stuff. I did the swap into my 1979 bronco and pickup. Pulled out all the unnecessary factory wiring, cleaned up and simplified the engine compartments too.

    Jess
    Previously owned;
    1979 Mustang, v6 swapped to EFI 393, custom installed m122 blower, 4r70w trans, Megasquirt II, T-top swaped in.
    1990 Mustang, 545 BBF, C-4 with brake, ladder bars.
    1983 Mustang, 1984 SVO Mustang
    1984 Mustang convertible, v6 swapped to 351
    1986 Mustang GT, 1989 Mustang GT convertible
    1992 Mustang coupe, 4 swapped to 302

  10. #10

    Default

    So I had some more time to work on it today and found some more stuff. I bought a new alt from summit it’s a performance alt that seems to work okay. Car charges now when I rev it above 2 thousand rpms the light will slowly get dimmer as the rpms go up until it goes off. The other alt would not do this. I went thru the wiring again and can’t find any issues. Checked my voltage regulator with a digital multi meter the green/ red wire on the regulator is seeing 9.7 volts while car is running, white/black is getting 3.5, yellow is getting 13.6, orange/blue is seeing 0.6 volts all with car idling. Bat is getting 12.8 both on and off. Starter selnoid is also 12.8 and the alt bat terminal is getting 12.8. If I disconnect the orange wire off the back off the alt and test inside the slip on plug I get 12.7 bolts on the black/white wire I get 1.7 volts. I did notice this by accident with the orange wire off the back of the alt the green/red wire sees 12.8 volts at the regulator (accidentally forgot to plug it back in) which is 3 volts higher than when it was connected. So now it’s charging at high rpm but not at idle. This alt deff is not bad. Maybe regulator has an issue. Not sure how much voltage each of these are supposed to have so I tried to get as much info as possible. Car runs fine and revs fine. Started to think my bat warning light could of been bad but it does go off once car is revved. Stock pulley size on the car nothing is under driven etc. all plug ends look fine. I’m about to order a new regulator and regulator plug just to rule that out and since I’ve been poking the wires with a test light and multi meter.

  11. #11
    FEP Super Member mustangxtreme's Avatar
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    I swapped 3g as well. JY alternator/wiring. Works fantastic.
    Dave

    If common sense was common wouldn't it just be sense?

    1983 Capri L T top 5.0 efi aod
    1983 Capri RS Turbo
    1981 Black Magic 400 c6
    93 F-250 351 5sp 4x4

  12. #12

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    I gave the stock type alt one more chance before I go 3g. 3g would of been easier. But I really wanna get this figured out if anyone has any ideas what to replace

  13. #13
    FEP Senior Member Tigger's Avatar
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    Have to taken any of these alternators to your local auto parts store and had them tested?
    67 Mustang Coupe
    96 Tangerine GT
    86 Saleen #179

  14. #14

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    I'm late to the party... I had a similar issue. I would get nothing out of my alternator in my 85. I tried 2 different alternators (1 reman and 1 known good) and 2 different regulators (1 new and one known good). Checked wiring it all seemed fine. I probably could've dug in deeper on the wiring (this car was a mess with the electrical back then). I decided to say screw it. I went with a GM alternator. Drilled out the hole for the long bolt and cut a piece of pipe to make a bushing to make up for the difference. Ran a wire to the battery from the hot post and another small wire from the number 2 (I think) terminal to the hot post. BAM charged great and I was able to remove the old harness and regulator to clean up under the hood. I've since upgraded to a 140 amp from summit. Its a ford style casing so no need to drill or use the bushing anymore but it's a one wire GM style. I also have one on my 79 F-100. I love them. So simple and they handle the power my sound systems need.

  15. #15

    Default

    I did not post an update but the new alternator works great from summit. I changed out my voltage regulator also just to be sure and now it charges fine at idle. Idk how many reman alternators I went thru more than I can count. Had the same issue with a reman alt on my buddy’s 91 gt. Just didn’t work. Seems quality control is pretty low. Once I put the summit alt on it would charge above 2,000 rpm but than once I changed the regulator it was all normal. Moral of the story avoid rebuilt alternators. Running all stock accessories even.

  16. #16

    Default

    What's "fine at idle"? 14+ volts?

    I hear you on a (lack of) quality control nowadays. I just went through a brand new (couple hours running, which can't be really called "running" because it didn't work worth a $hit, stumbling and staggering and pig rich etc...) Holley "770" (even the cfm ratings are BS marketing... 700-ish cfm would be accurate) Avenger, and prior to doing any of the normal adjust-ability modifications for super-tuning and precisely dialing something in I was going to do, first I had to clear out all of the machining debris that was floating here and there as well as one rather large piece of metal debris blocking one primary transfer slot. Lazy lacking quality control is rampant in all sorts of areas of parts sold today. The main reason I've been able to completely avoid rebuilt alternators for a handful of decades now, is that the great percentage of the time, all that's wrong with a good old or original one is that the brushes are worn out and/or broken off, and the shaft ends' lubricant is long gone or turned into glue. The $7 alternator brushes and a bit of time beats the hell out of the cost of a replacement.
    Last edited by Walking-Tall; 07-19-2018 at 03:05 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  17. #17

    Default

    I haven’t checked the voltage with a multi meter. But battery light is off and I drove about 40 miles with shutting the car off a few times during the trip making stops. All is well. Lights etc were on (driving at night). Glad that one is over. Replaced my colatage regulator connector also while I was in there. Easier just to do it all than have it fail down the road. I’ve also had similar issues with carbs. Needle and seats not sealing etc on my cars. Seems like no parts are 100 percent anymore. Which is a shame for what they charge for us to purchase them.

  18. #18
    FEP Super Member erratic50's Avatar
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    I’d check the grounds just to be sure things are in order.

  19. #19

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    Yeah I triple checked everything long ago. Couldn’t believe the alternator issues and second guessed myself. I re wired the whole car. Had it down to a shell and went through every inch of wiring. Easy to overlook stuff in a rebuild so i made a good effort to check everything. Can never be to sure

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