Okay GRMers, my local independent Honda guy is on vacation, and I need a hand figuring out what is wrong with the wife's civic before i give up and take it in to the dealer.
Recently, I had to replace the battery was replaced for a no-start. Since then, we've taken a long trip in the car, and I've noticed that the headlights / interior lights "pulse" while the engine is running. It does not seem to change with by engine speed, and the voltage is steady on my digital multimeter.
I suspected a bad voltage regulator, and opted to replace the alternator (regulator is internal) with one from the parts store. That did not resolve the issue. The car also has a new belt, and I replaced the positive terminal on the battery due to corrosion. Grounds and other connectors are all nice and clean/shiny/tight.
The car has one of the Honda ELD gizmos in the fuse box. I pulled the plug off and it's got battery voltage and 5v from the ECU like it's supposed to. Unplugging the ELD gizmo does not seem to change anything. I probably need to backprobe this thing and see if the voltage varies with electrical load like it's supposed to.
Checking the voltage at the battery with the car running, I get 14.4-14.8v depending on if i've been driving or not. If i unplug the 4 pin connector from the alternator, i believe it stops charging completely, as the voltage measured at the battery drops to 12.1-12.0 and the headlights dim a bit and stop pulsing.
Any input would be appreciated. Thanks!
For what it's worth, this sounds a lot like a problem that I had with a much older Civic a few years back. Same deal: dead battery wouldn't hold a charge, replaced battery, it went dead too, replaced alternator with an aftermarket rebuilt unit, battery died again, added amp meter and watched a steady discharge, had the replacement alternator replaced under warranty, battery died again. Suspected a bad ECU, parked the car and bought a brand new Civic.
The new car wasn't as much fun as the old one, so a month or so later, I charged the battery on the old car and drove it to the Honda dealer and paid them to find the problem. They said that I needed an alternator. I threw the BS flag and told them that I had already done that twice. He asked if it was a Honda alternator. I said "No", and he repeated that I needed a new alternator.
I sucked it up and dropped twice what I had spent on the rebuilt alternator for a new Genuine Honda unit. Then I drove the car for another 80,000 miles.
I had purchased two bad, rebuilt alternators. And a new Civic that I didn't even like. I got a refund for the rebuilt alternator and then I sold the the new back to a dealer after a year and 12k miles. I had gotten a great deal on the car and didn't take much of a loss on it. I took the cash and bought a Miata.
Woody wrote: replaced battery, it went dead too
I don't seem to be having that problem at least.
I've meant to swap the battery with the one in the miata just to see if it's something funky with the battery, I'll do that and try backprobing the ELD gizmo this afternoon and report back.
gamby
SuperDork
1/1/10 6:27 p.m.
My 95 Civic hatch just had alternator issues.
My mechanic had it for a week because an entire batch of alternators had bad regulators on them. He went through 4 or 5 before they got one that worked. 
Symptoms were--battery intermittently wouldn't hold a charge. Car would still run--even w/ the battery disconnected.
Runs like a top now, though...
