Alternator/ Battery light???

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flydex28

flydex28

Senior Member
So two years ago i replaced the alt. in my car with a carquest one and it was fine until a few weeks ago. I was driving along and the battery light came on.. I took it to knects auto parts and they told me the alt. was bad so i ordered a replacement from autozone as they were the only ones who could get me one the same day. anyway.. two days later the same problem... light comes on for 5-10 seconds then goes out... I took it to the NAPA here in town and they told me the same thing after hooking it up to their machine while it was still in the car... the alt. is bad.. well this just pissed me off so i ordered one from Honda and installed it today.. guess what? same thing; i'll be driving down the road and the light comes on for like ten seconds then goes out. What could it be? Ive tried wiggling wires to see if i could make it come on again but cant.
 
is the belt loose and slipping maybe? other than that, it has to be either a poor connection in the wiring, bad wire(s), bad alternator(which you pretty much ruled out at this point), or your battery is going bad(not taking a charge).
 
Well im gonna take a look at the connections and the grounds today. Maybe try and see if I can get the battery replaced under warranty.
 
So heres an interesting thought... does the size of the battery cables make a difference? I just noticed that the battery cable from my old engine (d15b8) is a different size from the new engine (b16sir2). also, does this apply to grounds as well?
 
So this is getting to be ridiculous; I cleaned all the grounds and used new bolts on them, I also noticed some corrosion on the positive battery cable in the wires themselves at the clamp so I cut like an inch off the end so i was down to nice shiny copper and attached a new terminal clamp, light still randomly comes on...usually when i let off the gas like at a stop light... but not always.:confused:
 
Let me share some generalities. Poor battery condition increases demand on alternator and can shorten lifespan of alternator. How much is a case by case thing - depends on age of alternator and capacity. Battery terminal issues such a loose connections and corrosion count against battery condition.

A poor performing alternator will shorten battery life as battery life is a function of charge condition over time pure and simple. A battery that's maintained at 65% charge condition will not last as long as a battery that's maintained at 90% charge condition. Temperature and load also play a factor, but let's not coufuse things with that.

Battery condition and alternator condition are therefore related. In many cases, a poor alternator over time will cause premature battery failure. So, one replaces battery only to have the new one live a short life due to poor charging condition.

Conversly, a poor condition battery will place increased load damands on the alternator and can cause premature failure of the alternator.

What I'm saying is many times both need to be replaced. When replacing alternator the battery should be fully charged using an external battery charger and then load tested to be sure it's ok and not damaged from a crappy alternator that the performance deteriorated over time taking life out of the battery. When replacing battery, the alternator should be removed and load tested.

I've read several times over the past few years that major chain store aftermarket alternators that have a lifetime warranty are junk. I used them for years and trashed a couple of good Optima batteries using them. They are junk.

I still use Optima batteries but now run an aftermarket 160 amp alternator. Much better, lights are brighter in the car, ignition fires better, fuel pressure is better as battery charge condition is maintained much better. This will extend battery life and I don't have to replace the alternator once a year or so.

I've read the OEM alternators are also good ones, although expensive.
 
Ok so ive determined that the alt puts out a constant 14.6 volts. The lowest Ive been able to get it with everything on in the car is like 14.3v. I also noticed that when the battery light turns on.. the voltage never changes. I know the White/blue wire coming off the alt. goes to the warning light and i believe it gets routed toward the underhood fuse box. I took out the underhood fuse box to look at the ELD and after the test where you should get appx. 2 volts, I got 1.8v. What does appx. 2 volts mean? Also where is the ground to this fuse box?
 
most modern alternators have a voltage regulator on them so they don't overcharge based on revs. it really sounds like it's your battery, not the alternator. Have you tried swapping batteries with a buddy? even autozone will run a test for free
 
easier said than done... ive had the battery checked at napa and knects here in town and they both say its good... although i dont really trust either of them; both autopart stores here in town dont know what they are talking about most of the time... for example... one guy the other day tried to tell me the second wire coming off the positive battery cable was a ground wire. We dont have an autozone here and the closest one is an hour away. I really hate this town i live in. Im gonna try to get the battery exhanged... its a Knects battery hopefully they will do it.
 
The cables could be bad from corrosion that you can't see. Ground connections to the engine, etc.

One way I've tested for this in the past is to turn on headlights and hit the starter. If doing it alone, you will probably want to do it after dark so you can see how much the lights dim when the load of the starter kicks in. They shouldn't dim much.

That's a down and dirty method, but if the battery is hot and there are cable/connection issues they will generally manifest with lots of load on them. You can run wipers and heater blower motor also and high beams on the headlights.

Disconnect the distributor plug and just crank it a bit with the other load on it and see how it does. A fully charged battery that's in good condition will spin it over no problem. If not, then it's about figuring out if it's battery condition or connections.

There's a fuse somewhere between the alternator and the battery. Probably in the fuse box under the hood. When in doubt replace it. You have a swapped engine in the car? What shell is it?
 
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Its a 92 civic cx, i put the b16sir2 into it. I was told to also check the ground on the fuse box just not sure where it is.
 
How old is the battery? Try the "Oklahoma load test" I suggested - be sure it's fully charged. I don't know locations on that model as mine is a 1991 that I work on and am familiar with.

Get yourself a Chilton or Helms manual for it.

Reading through your posts again, you have had the battery load tested at two places and both claim it's ok. I am suspecting wiring as in cables or the charging system isn't doing it as in wiring issue in the charging system.

Another thing you can do it run a jumper wire from the hot post on the alternator directly to the positive terminal n the battery - use a piece of straded #8 wire and only use it for testing as it will be unfused. If no change in condition, that will eliminate the charging circuit. All that's left beyond that, if it's wiring will be the grounding.

The load test I suggested will also tell you if wiring and connections are sound.
 
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Battery is two years old. "Oklahoma load test"...LOL. I will try it, but which distributer plug? Another thing I noticed last night is most of the time the battery light is off but if i turn on the heater or lights it comes on... if i turn them back off it usually goes away, although the voltage only shows the normal minimal drop. Im wondering if there is a sensor in there somewhere that is telling the light to come on if it shows even the slightest drop in voltage.
 
What you are describing is the alternator not holding the load. Alternator is junk or charging circuit ain't gettin' it done - wiring issue, corrosion, etc.

Alternators can be limp and run for years. Losing 1 diode in the bridge will diminish performance, but not to the point of total collapse of the electrical system.
 
But if its not holding the load why is the voltage always good... like i said even with all the electronics on in the car its still showing 14.3volts. I guess I just dont understand.
 
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