2 Alternators later

chevis_regalchevis_regal Member Posts: 4
edited August 2015 in Honda
I apologize ahead of time for the length of this.

As I pullout of my drive way one morning, I hear what appears to be that weird alternator whine sound. As I continue to drive, my batter light comes on and and its all down hill from there. After all of the electrical components (radio, a/c, windows and steering) in my car completely shuts down on my way to work, I coast to the side of the street. I bring it to a guy who I trust and has done work on a few of my other cars over the last 8 yyears. I tell him I got a new battery from Autozone about 4 months ago, and he tells me to return it and get a fresh one. I do so, and when he puts in the new battery, the alternator starts to smoke. He replaces the alternator, and I'm felling good. The following morning, as I start my car, it hesitates but does start. I turn it off, start it again...and the same thing happens. So now I'm no longer feeling good, but my car is running so that's progress. The next day, my car starts right up...everything is good. On my way to work the following day, my battery light comes on again and I'm like oh [non-permissible content removed] not this again. I stop by the same guy, and he tests my battery and alternator, and he tells me they both check out perfect. However, he says just because its a new alternator, does not mean its not the problem, so he replaces it. After this my car is rolling again and I'm feeling good once again. Now after a few days, my battery light is coming on and off periodically, but does not stay on for more than 3 to 5 seconds. I know I can bring it back to my guy again, but what are some possibilities that I can explore personally as to save myself some time and money.

Any assistance would be greatly appreciated and I again apologize for the length of this post.


  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    Always trying to think simple... is it possible the belt is slipping, causing a reduced output voltage? Sort of feels like it.
  • chevis_regalchevis_regal Member Posts: 4
    Dumb question...but is this something I would be able to visibly notice. Also, I assume that If I have already had 2 alternators installed within 1 week, that my mechanic would have noticed this as well. Also, my battery light never comes on immediately when I begin driving. It usually starts after i've been driving for 10 minutes or so, and sometimes will not come on at all after a 15 minute drive.
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    It's not likely that you will see that the belt is loose, but you can do a quick check to feel if there's enough tension. Here's a short video showing you a quick test of tension on the belt.

    Sure sounds like the belt is slipping is at least a possibility. Think about what's happening now. The car starts and runs normally, but after a period of time, the battery light comes on. If the belt is slipping, it's also heating up, and expanding, getting slightly looser in the process. The alternator output drops, the battery light comes on.

    Still could be something else, but the belt tension is a simple one to look at.
  • chevis_regalchevis_regal Member Posts: 4
    Thanks for the response. So I'm curious...If this has been occuring after having 2 alternators installed, does the belt need to be changed at this point or just tightened. I'm asking because I assume my mechanic knew to look at this at the very least during the second install. Also, after the last alternator was put in, I have yet to return to my mechanic....whats the best way to explain my current situation. The reason I'm asking is because after the last install, he said everything should be fine after he drove it for a while and didn't get any battery/voltage indicators. I guess I want to make sure he doesn't look at it again and say nothings wrong....if you get what I'm trying to say.
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    Assuming the issue is the belt, it may just need to be properly tensioned, or it may need to be replaced. Here's a good page describing when a drive belt should be replaced

    I go back to the mechanic and be straight with him and NOT confrontational. The problem is recurring, I think it might be the belt since I'm assuming the replacement alternator is good and a loose, slipping belt might explain what's happening.
  • chevis_regalchevis_regal Member Posts: 4
    Sounds good. Thanks for the help and i'll let you know how it turns out.
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    Fingers crossed for you. ALWAYS nice when things stay simple
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    Could also be a defective belt tensioner. The mechanic should also scan for trouble codes. You could also have ECM/PCM (brain) damage, or faulty wiring between alternator and ECM.
  • thecardoc3thecardoc3 Member Posts: 5,557
    The charging system lamp is controlled by the instrument cluster microprocessor. The instrument cluster can turn on the charge lamp by itself if it see's its own system voltage falling below a specified level, or if another module such as the PCM or BCM experience an issue and request that the lamp should be on. The electrical load is measured by the ELD (electronic load detector) in the fuse block which reports how much current the vehicle accessories are drawing to the PCM. The PCM also monitors pin L of the alternator which informs it as to how hard the alternator is working in order to achieve its present output level. The PCM can command the charge set point of the voltage regulator by either leaving pin C open (normal charge level) or by providing a ground for pin C which will cause the alternator to reduce its output to 12.5-12.7v

    Charging system problems that result in the PCM commanding the instrument cluster to turn the lamp on will set trouble codes which can be retrieved and that will help with the diagnostics. If the tensioner is suspect the easiest way to prove that is to measure the system voltage at 2000-2500rpm. Then turn on every possible accessory (headlights, AC, high speed on the blower motor, headlights, rear defogger, heated seats etc.) which will result in the alternator having to generate its maximum current output. If the belt starts slipping, you should be able to hear it, plus the system voltage would hold up to a point and then drop below the specifications and you should get your warning light.

    BTW some aftermarket alternators simply don't perform to the PCM's requirements and a random warning lamp is common. The shop might have to go with a different source for the replacement alternator.
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