I've been working on this car for about 3 months now, picked it up in terrible condition...lots of ghetto repairs, missing parts, hidden damage, etc. Currently I'm trying to figure out why the alternator doesn't seem to be keeping the battery charged.

Sometimes with the car running the voltage reads about 11v...sometimes it reads 13.8v. This happened with the alternator that was on the car, and the brand-new one I picked up a week ago. Today was the first time I started the car with the new alternator, for the first few minutes any time I would turn on the heater or turn on the brights, one of the pulleys would scream...it never did this before, but it would go away if I gave her any throttle. Doesn't seem to be doing it anymore, though. I also noticed quite a bit of drain if I turned on the headlights/brights.

The first alternator was bad, this one was tested before I left the auto parts store with it so I know it's good. Right before I shut the car off after 15-20 minutes of running, the voltage was at about 11.6v...I shut the car off, started it back up and the voltage was then reading 13.8v, didn't throttle it or anything, only let it run for a few seconds. What would cause the voltage to read so low, but go back to normal after the car is restarted?

As for any wiring that looks bad under the hood...all the wiring in the front passenger corner by the headlight looks like a rat's nest. All my lights/brights/signals work fine, most of that wire mass is the rad fan wiring and a/c wiring...both of which I do not need. Should I delete the un-needed wiring and see if that solves the problem? Also...could there be some voltage-related component somewhere that may be bad? I remember something about a voltage regulator in the fusebox on some Hondas, maybe I have that and it **** the bed?

 

Have you checked the battery? I had nearly the same problem, and it turned out to be a bad battery. It would give a "decent" reading but was bad.

 

Same issue with two of the same brand/model battery, and I know they're good because they both were used in other vehicles to "test" them...the second one is still being used in a family member's vehicle with zero issues.

I guess it may be worth mentioning that my "voltage reader" is a Cobra radar detector, since I couldn't find my multi-meter. It's a good radar detector so I'm assuming the voltage reading is accurate, but I'll track down one of my voltage gauges or a meter tomorrow just to be sure.

 

You need to check all your grounds under the hood.

 

Ah bummer. I just kept overlooking the battery since it wasn't that old and it would give about 11.5 which always seemed ok to me.

Good luck with it.

 

Those grounds definitely do look pretty whooped, and the battery cable terminals are whooped as well. I have sections of bigger gauge cable with gold-plated connectors that will make good ground cables, and I should probably stop by the 'zone for some new cable terminals while I'm at it.

 

Bad grounds will cause major issues. Your main ground at the battery, your trans ground, valve cover ground, thermostat ground, as well as check your ground boxes on each side of the frame rails which is the main ground for your lights and what not. I myself added a 0 gauge engine block ground as well since my battery is relocated to the trunk. Also realize that battery voltage when the car is off should be 11-12 volts and a good running car will read 14.2-14.4 volts.

 

Voltage while running didn't pass 13.8-13.9v, voltage when off was around 11.5-11.6...after turning on the parking lights, turning the key on a few times to read CELs, it dropped to around 10.4-10.5. Since I got this car it hasn't run more than like 20 minutes. Since the new alternator install and jump earlier, it didn't run for more than like 15 minutes. Should probably let it run a little longer once I get some repairs done.

I'll definitely replace those grounds and battery terminals tonight or tomorrow, since they're pretty shot. I think there's only one ground coming from the battery and it goes to the chassis, then to the trans. The other is from the valve cover to the core support. I'll beef those up and maybe add a third ground in the mix. I'll post an update if I see higher readings.

...On the bright side, I now have heat in the car. Last heater core was shot. I hope to never replace one of those again on a Honda.

 

I'm running brand new grounds, with the contact spots and the bolts holding the cables cleaned up. I deleted the a/c harness under the hood.

When the car is running, nothing on, rad fan turned off...I can get it to about 13.4-13.6 volts. If I turn on the rad fan, heater on max, headlights on and set to bright...the voltage drops to 11.2-11.4 and will up up 1-2 volts if I throttle it. It will not go back up and stay until I turn all that stuff back off.

I have turned the car off and on several times, the battery seems to be holding a charge, and the car will run with the battery disconnected. The idle, with everything off, doesn't even stay above 13v all the time, either...sometimes it's up there, sometimes it's down in the 12v range. I don't believe it is the battery since it works fine in other vehicles and does hold a charge, and I did let the car run for about an hour today...something else wrong, or should I throw my voltage meter in the fireplace?

Edit: My Chilton's manual does have a definition for what the ELD(Electric Load Detector) is...does this car have one, and if so...if it was failing or already bad could it cause the above issues? If I do have it, I'm not even sure where it is...fuse block under hood if I'm correct, but I don't recall seeing much of anything in there besides fuses and wiring.

 

IIRC the voltage regulator is built in the alternator. Everything you say seems to indicate that it's a bad alternator, especially the fact that the voltage drops when you turn on the accessories.

Take your alternator to Advance Auto Parts and they test it for free. Then you know for sure

 

I just bought this alternator and it was tested before I left the store with it. I guess I can take it back off and run it up there for another test...but I'm pretty sure it's good. I have to run up there to buy a new master cylinder, anyways.

 

Took the alternator back in today, passed all tests. They exchanged it out anyways and got me another that has a Mitsu casing but came with a little flyer that says "appearance will differ from normal model" and explained that it will fit my car and meets/exceeds oem blah blah blah.

So anyways, either their alternator tester is bad and the voltage regulator is actually bad in that alternator...or the problem is elsewhere. What else would cause the voltage to not recover back up to 13-14v when a bunch of crap is turned on while the car is running? I won't be able to test this new alternator until tomorrow, but since the first alternator tested fine I'm assuming the problem will still be there.

 

The fact that your car runs with this rat's nest you speak of shouldn't be anything short of a mild miracle. Clean the wiring up, check your grounds. Replace ALL corroded wiring. Don't even bother trying to clean them up. Just tag it all (if need be) and replace. Get a nice clean wiring setup going and you'll be happier in the long run. It sounds like it's just an old car. These car's weren't meant to keep up 100% at 20 year later range. Ya they work 99% of the time but not at peak potential this long later. As long as it runs/your lights are bright enough/it doesn't feel like it's going to stall then all is 'well.'

But realistically, think about it, the reason it probably doesn't run so well is because of some wiring that's grounding out somewhere.

 

I've already cleaned up all that wiring, completely deleted the a/c harness, installed new battery terminals, replaced the old and very beat up battery ground cables with two brand new ones. The new ground cables are bigger gauge with gold connections, and where they ground at were cleaned prior to the install. One goes to trans, one goes to chassis. I also replaced the VC-to-core support ground and cleaned the contact areas for it as well.

I could see how the age of the car may reduce performance a bit, but the fact that the alternator does not kick up the power output at all when a bunch of stuff is turned on seems more like a component failure somewhere rather than degradation due to age...especially when the battery and the alternator are new. Hopefully I'll notice a difference today with this new alternator.