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  1. #1
    OVER-BOOST!! svono50's Avatar
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    Charging issues...

    Long story, but I know this is pretty common with our cars, but since I installed the old Pat-in-LA upgrade wire many moons ago, I have been trouble free. I started to notice 1-2 summers ago, that my AMP light would flicker a bit when I started up the car, but never light up fully or steady or even every start, it was pretty random. When it did flicker, it would always stop and go out after a few minutes of run time, so I figured it was just a 'typical' 30-year old car quirk that I didn't have to futz with. Well, my battery this spring did NOT want to come back to life, even after sitting on my battery maintainer for 2 months before the first start. Now, it was 7 years old, so it was getting 'old' and I was not completely surprised, but I still had this feeling that the flickering AMP light may have contributed to its passing.

    I purchased a new Motorcraft battery that was rated at 590CCA and tested out at 670CCA, hey, bonus! Battery has been working fine this summer, but I still had the flickering AMP light on startup and even noticed it would sometimes reappear while driving after even 20-30 minutes. Now my lights never showed signs of dimming at idle or any bad running issues during any of these times. My battery voltage during idle was showing 14.5V and 12.6V when off, so all is good, right? I did another quick test on the battery last week and it now shows 430CCA...HUH?!? The thing is only 3 months old, its capacity shouldn't have fallen off that fast, IMHO.

    With the 'good' running voltage, I wondered if my regulator was finally throwing in the towel. I ran some tests to see if I could spot the issue, but nothing seemed to show as 'bad'. I purchased a new Motorcraft regulator and tossed it in, figuring it was worth a shot. First couple of starts showed a 'silent' AMP light, good deal, right? Well, on the 3rd start it was back...grrrr!! So was it my alternator getting flaky? Not sure, I ran over to Napa and picked up a rebuild unit to have on hand if my next steps show it was truly bad.

    Time to pull out the ol shop manual and start going through the troubleshooting steps to see if I could figure this out. Wow, I didn't realize the amount of steps they spell out for fully diagnosing the charging system, all based on very specific conditions...one of which is a 'flickering' AMP light, go figure! One of my first steps was to check the voltage with no load, good there. Next up was voltage with high load, good there too. I then checked to make sure the voltage at the alternator battery terminal was the same as at the battery, yep good again. What can trigger the AMP light is too low of a voltage out of stator terminal that closes a switch in the regulator and energizes the AMP light circuit. The stator voltage should be ~1/2 the battery terminal voltage, so a 14.5V battery terminal should result in ~7.2V stator terminal voltage...yep, good on that one too. Of course, at this time my AMP light was off as it should be with the stator voltage where it should be. So my next step was to make sure all connections on the alternator were still clean/good. I disconnected the battery, popped off the field terminal from its post and all was good, shiny and clean. Popped off the stator terminal and noticed the post moved a bit...hmmm. Sure enough, the nut that secures the terminal post was loose. I tightened the nut, then checked that the field terminal nut was tight and it was. I plugged the two terminals back in, hooked up the battery and fired the car back up. Everything showed proper voltages and there was no AMP light, which was encouraging. Alternator remains sitting quietly on the bench in its box.

    I have only had 2 additional restarts since the repair on the loose stator terminal and not one episode of a flickering AMP light. I want to get some more run time on the system to see if my battery has picked up some additional CCA above that last test. If all is now 'steady' on the charging system, I don't see why not, but time will tell. I will report back in a couple of weeks with the results.

    Whew, I hope I didn't cause too many of you to doze off there
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  2. #2
    OVER-BOOST!! Bruce's Avatar
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    My amp light has been acting up for the last few months of last season and the start of this one. I thought it had to do with the loose wire from my plugged low oil light. Got under and re taped it and it went out. A few days later its on again. I have done the 3G swap and checked all the wires in that jumper set up and it went out. Now its back again. Never a problem with the car running or going low on power. Checked voltage across the battery and its good so I am driving it right now.
    Bruce

  3. #3
    OVER-BOOST!! svono50's Avatar
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    Little update. Last night I swapped my original voltage regulator in for the Motorcraft unit I put in earlier. Fired it up and the AMP light turned right off when the engine fired over, so that is an encouraging sign that the loose stator post was the source of my issue. I will give it a few more cold start cycles to confirm and report back...fingers crossed!
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  4. #4
    OVER-BOOST!! svono50's Avatar
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    Update #2: I took my car into work today to give it a little exercise on my 36 mile round trip, mostly highway. No AMP light issues and ran great. After dinner I ran a quick battery test to see how things were and was greeted with 545CCA and 681CA readings...hurray! Looks like things are moving back in the correct direction and the loose stator post appears to have been the root cause to the issue. Weather looks good enough to run it to work again tomorrow, so some more exercise for its systems...
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  5. #5
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    I swapped in a GM style one wire alternator. Connects directly to the positive side of the battery or starter relay. No issues whatsoever.

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