Possible electrical charging issue

Discussion in 'F-250 and F-350 General Tech and Info' started by Bdons-SD, Dec 18, 2016.

  1. Bdons-SD

    Bdons-SD Anti spark plug!

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    Hey guys, anything electrical typically goes right over my head. I have basic knowledge of automotive electrical systems. With that said here's my issue:

    Headlights are dim at idle, brighten up when I give it gas
    Vent/defrost blower slows down at idle, speed up when I give it gas
    Battery light intermittently comes on. Blinks once or twice then I don't see it for a day or so.

    Here's what I've checked:

    Tested batteries at shmoreillys, they're good, but charged at 70%, alternators good on the running test. Also had the alternator bench tested 3 times. Batteries are 4 months old, alternator is about a year old.

    I checked the voltage, 12.2 on both batteries while engine is off, about the same when engine is running, it wasn't running long after sitting for 2 days so it could probably use a re check. But I figured as long as it isn't below 12 I'm good. Alternator is putting out 14.5-14.7, both wires on the exciter plug are putting out 12.2.

    I'm ordering a new exciter plug since I know it's a common failure and it could just be wiggling around causing my battery light, the headlights and vents are what confuse me. Any help would be appreciated. Thanks!


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  2. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    Fully charged batteries should be 12.6 - 12.7.
    Each cell in a 12 volt battery makes 2.1 volts.
    So what seems like a drain at idle is the
    batteries trying to charge up to 12.6.

    Takes 15 minutes of driving time to charge a battery from one normal engine starting.

    People who make 5-7 short in town stops and engine starts usually
    have drained their battery by the 6th or 7th start because
    they haven't had enough engine run time between starts
    to fully recharge the battery.

    Not saying this is your case,
    maybe you have a unseen battery cable issue, either that or ground to the engine block. Check that connection it is clean and tight.

    Its not beyong the realm of possibilities you could
    have vibration damage to one or more of the grids in
    the batteries causing
    them to not fully charge past 70% even with them being fairly new.


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  3. Bdons-SD

    Bdons-SD Anti spark plug!

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    Thanks for the response Joe. Here's some changes after playin with it yesterday:

    I checked the voltage on the batteries this morning after my drive to work (25 mins), they check out at 12.74-12.75. Now, after I unplugged and fiddled with the exciter plug/ alternator pigtail, whatever you want to call it, the battery light came on when I first started the truck, stayed on flickering through warming it up, even with my high idle tune kicking in and it idling at around 900 rpm, then it went off when I started driving and didn't come on again at all.

    I ordered a new pigtail last night, as of now it looks as though everything is charged/charging correctly. If you can think of anything else I should check, let me know, thanks!


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  4. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    Sounds like it was low batteries not fully charged.

    Guess you had a hunch the pigtail was
    the problem or corrosion on it's contacts.

    Clean those metal contact prongs on the alternator
    that the pigtail attaches to with a small blade
    screwdriver before you put the new pigtail
    on and put some dielectric grease on the contacts
    before plugging them together the final time.

    They sell it in a small pack called bulb grease.

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  5. Bdons-SD

    Bdons-SD Anti spark plug!

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    Well, this issue has been on going for a few weeks now, progressively getting worse. At first I thought it was just because of the cold, but it's warming up a bit without any change. So without any other real symptoms that are affecting the truck, I'm really just going down the line on common issues I've read about. The pigtail being the second most common next to a bad alternator. Luckily up here in WA rust and corrosion isn't really much of an issue on a daily rig, especially for a 1 year old alternator. But I will inspect the contacts and add some dielectric grease to them. Though when I pulled the alternator yesterday the main power post is still shiny like new. I've recently went through and wire brushed all my battery posts, and connectors so they're all nice and clean. I guess if the pigtail isn't the issue I'll have to inspect the fuseable links (my engineer buddy suggested that), or maybe I have an open circuit somewhere drawing power. GPR possibly?

    I'm also having a cold start issue, I chalked it up to cold thick oil not building pressure quick enough to fire the injectors. Nice cloud of white smoke on start up, with a rough idle. Truck starts like a dream of I use my block heater. Maybe my GPR is faulty? Is it possible for that to draw power while not powering the glowplugs? This is where the electrical stuff gets lost on me ha ha.

    Thanks joe!


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  6. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    Our trucks are notorious for the BCM (Body Control Module) being a current drain.
    No one has a BCM available,
    the only source being pull-a-part
    yards or individuals parting out trucks.

    I just keep a Schumacher battery tender type smart charger
    On mine while it's in the driveway with its new
    Interstate batteries I bought this spring.

    If your GPR was the culprit, your glow plugs would completely drain the batteries within 8 hours or overnight.

    I'd unplug the fuse to the BCM but having power
    door locks and the domelight on/off being controlled by the
    doorlock actuators don't make sense having to
    pull the domelight fuse or bulbs out either.

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  7. Bdons-SD

    Bdons-SD Anti spark plug!

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    I'll keep that in mind, joe. Thanks for the advice. I've been meaning to get a battery tender for it since I got the mustang to drive daily, the truck sits for days at a time. I've been replacing the top on the mustang and the cold weather has put a halt on that for a couple of weeks so I've been driving the truck a lot.

    I'll update once I get the new pigtail installed. So far the symptoms remain the same, battery light only on at start up and flashed randomly while driving. Voltage reading on the dash doesn't change while driving, I even turned on ALL accessories I have on full blast and it didn't budge, or cause any problems. I don't mind throwing a $10 part at it before I go nuts on this things ha ha.


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  8. Bdons-SD

    Bdons-SD Anti spark plug!

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    So after the glow plug fiasco, I was still having this charging issue. Except instead of flashing in start up it would only flash at high rpms (2500-3000), once the truck would shift it would shit off. Since it wasn't causing any issues I procrastinated on fixing it. Alternator had a lifetime warranty so after talking to a shop they said it was most likely the regulator going bad. Usually AutoZone doesn't warranty their alternators unless they fail the test, but after a bit of explanation they swapped in under warranty. Popped it in and no more battery light!


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  9. Pity7700

    Pity7700 oh umm...uhh?

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    Glad you figured that out. Chasing that stuff down blows.

    Ive had alternators in the past with intermittent issues. Would charge battery fine one day or even weeks and then one day not work, next day it would. They usually test out alright at the auto stores too. Crap can give you a headache.
     
  10. Bdons-SD

    Bdons-SD Anti spark plug!

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    Yeah, it was definitely getting old fast ha ha. I really need to quit buying from oreillys and auto zone. An alternator should last more than a year, and brake calipers shouldn't seize up once a year. It's so convenient though! They all have lifetime warranties, but that doesn't do me any good if something goes bad up in the mountains or something. Buying stuff online involves too much vehicle down time ha ha.


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