Electrical Problem '86 Accord 2.0 EX

[ekntra]

hello, i have a freaky problem with my battery/wiring/"dynamo"(alternator?)

when my car is running idle, i check my power "status" on my battery with a volt-meter, it reads 14.7volt, when i turn on "driving lights" it goes down to 14.3volt+/-, that's ok by me... but the problem is when i turn on the "high beam" it instantly drops to 12,5volt and if i leave it on it keeps going down, i put on the "fan" in the coupë on full throttle and the voltage drops even faster, i've seen it down to 10,9volt at lowest, and on the instant i turn off "high beam" and the "fan" the voltage goes up to 13volt and counting up to 14,xvolt

at the same time, if i dont use any lights and give it gas to 3000rpm the voltage also drops a bit and if i go up to 7000rpm (i know you're not supposed to go into the red-zone) the battery lamp lights up, and the dynamo/alternator stops charging completely until it goes down to about 6000rpm.

I have tried to change battery and dynamo, actually im on my 3rd dynamo now... the dynamo's have been taken from scrap-accords, so they should be original...

does anyone have a clue what might be going on in my car? i didnt have this problem 2 months ago.

Jan

[A20A1]

I have no idea, might be some internal thing with the alt. I could just bee too much drain. Maybe check the ground wires and other electrical wires.

Do alts have voltange regulators? Maybe thats it.

[Deadhead]

sounds like your alternator is not handling the load as it should, go to autozone or some other local parts store, then have them check you battery and alternator.

[Soundy]

These cars have an alternator with internal rectifier and electronic regulator. In this case, it sounds like the rectifier pack probably has one or more bad diodes, similar to what happened to my '87 recently.

If you're really hardcore, you should actually be able to open up and repair the alternator while it's still in the car - undo the adjusting bolt, remove the belt, swing it out a bit, and you can disconnect the wiring and take the back cover off and remove the brush holder, regulator and diode pack. I have done this myself :)

http://moltenimage.com/freebies/g3accord/engine_electrical/24-20.JPG

If you have a multimeter with diode test function, you can test the diode pack:
http://moltenimage.com/freebies/g3accord/engine_electrical/24-21.JPG

If not, you're probably best to take the whole thing to an alternator shop to get it rebuilt - and I mean taking the whole car, as removing the alternator can be a real PITA with the G3 Accords.

General alternator output test procedures:
http://moltenimage.com/freebies/g3accord/engine_electrical/24-18.JPG
http://moltenimage.com/freebies/g3accord/engine_electrical/24-19.JPG

[ekntra]

but how can it actually be my alternator? i've changed 3 times(that's 3 different alternators), and every time i "accidently" hit 7000rpm they stop charging, now im not a handyman, so i dont know much about cars and until 2 days ago when i fixed the "start-engine" i didnt like to touch anything with oil on/in it, anyhow if i was to think of any reason it should be the wiring, but could a short-circuit wire in the path from alt. to battery be able to knock out the alternator?

[Soundy]

It's possible something else is sucking way too much power and frying one or more diodes in the rectifier... possibly a short from the charging wire to ground, maybe somewhere that it passes near or through some metal and the insulation is worn off through vibration, allowing it to contact when you rev to high and the engine moves on its mounts. When you replace the alternator, you're replacing the rectifier and regulator along with it, so it's not like there's anything else related to the charging system that could still be bad.

First thing you could do is follow the above test procedures on one or more of the alternators you've gone through, and see if any of them are actually failed, or if they're fine on their own.

Hmmmm, looking at the schematic, the main output does feed pretty much straight to the ignition coil, so if the coil has a short and is drawing too much current, that could cause problems at high RPMs... HOWEVER, there is a 40A fuse in that line that should pop LONG before the coil was pulling enough current to fry the alternator electronics.

Maybe test and/or replace the coil... AND check that 40A fuse (listed as #25 on the schematic). It's possible if it blew, and was perhaps blowing often, someone just replaced it with an over-rated fuse or just bypassed it, which might allow the coil to draw excessive current.

Charging/ignition diagram is here:

http://www.moltenimage.com/freebies/g3accord/engine_electrical/24-3.JPG

[ekntra]

all i was able to perform was to change coil, i changed to a coil that was mounted in a 85' prelude, it was the exact same, the car started with jump-start, but as of now it seems the battery dont get ANY power at all from when the motor is idling :/ i've tried to change back and forth again but it still wont charge :(

[ekntra]

btw, an update on how low voltage i've seen on it is now 8volt, and i would like to say "IT HURTS TO BE ME!"

[Soundy]

Get thee to an alternator shop, is all I can suggest then... they've got a big machine on whieels that they'll hook up to your car and figure out in about 30 seconds where the problem lies...