Alternator light weirdness

rennch · rennch's Garage

Ok...a little background. I have a 72T with a 79 3.0 motor in it. (Yes, it goes...)

I've got a battery swap for an odyssey race battery, relocated to the passenger side battery compartment. Recently, I replaced the Alternator, and all has been fine until I swapped for a non-revlimiting rotor in my distributor. (Never mind why there was a rev limited rotor there in the first place)

Now, *very* intermittently, my generator light flickers for a while, and then seems to eventually go away. The other day, the generator light was on, and then I spiked the motor to about 4000 rpm, and it disappeared for good. ANY ideas why this might be?

Thanks,

mto

304065 · 10-28-2003, 10:32 AM

Oxidation of the blue wire D+/61 circuit. Do a search on "D+/61" and there is tons of stuff. Has NOTHING to do with the dizzy rotor.

rennch · rennch's Garage

I suspected as much. This car has lots of electrical problems due to oxidation. For instance, I just filled my gas tank, but the fuel gauge shows "E". The next time I get in the car, maybe it'll show a quarter tank or so, or maybe a full tank. Good times.

rennch · rennch's Garage

Bump.

My battery is dead now...it shows the alternator is not charging the battery. I just bought the Alternator, as a good used version, so I think it's ok. I've got it partially torn apart, but I haven't removed the off-white air ducting.

The "search" won't let me search for D+/61 or just D+61. It says it's too short of a string.

Anyone help?

rennch · rennch's Garage

Update: Checked the continuity of the Blue D+/61 wire...everything seems to check out. Anything else I should test/check, or is it likely it's a bad alternator? Seems unlikely...I just bought it recently.

304065 · 11-04-2003, 03:27 PM

Bad voltage regulator. Swap it with a known good one.

rennch · rennch's Garage

did that. I have 3 spares.

304065 · 11-05-2003, 06:30 AM

So when you pull the blue wire off the alternator and ground it to the engine block with the key on, the warning lamp glows brightly.

You changed out the VR with a known good spare.

And you are still getting a dim glow from the lamp.

You say the battery is dead now, shows the alt not charging. That could be true, but the only way to be certain is to run the car and put your voltmeter on the battery terminals. If you get less than about 13.8v, then it's a bad alternator or bad connections (see below).

The last thing I would check before concluding it's a bad diode are the connections on the back of the alternator, at the 14-pin connector (both female and male) and on the VR socket. Hit the VR terminals with an abrasive (emery cloth or something) to clean them bright, a q-tip with some denatured alcohol or electrical contact cleaner on the socket terminals everywhere. The charging current comes out of the B+ terminal on the alternator and runs forward to the starter, connects there and then runs to the battery. If there is a ton of oxidation somewhere that could be creating a high resistance, pulling the voltage the battery sees down to where it won't charge (unless you run the car for hours).

I would charge up the battery for 24 hours (not overnight), start the car, check the voltage at the battery terminals and then start tearing apart.

rennch · rennch's Garage

John,

Thanks for the help so far. Here's where I am:

Got myself a multitester, and tested the voltage at the battery, with the ignition on, and off. Off, it reads around 12 or so. On...it read around 12 or so. "Ok then...alternator must be bad, or a wire might have come loose, broken". So, I popped the fan out, and checked the wires...looked ok. I decided to take my Marchal alternator (a spare) to the local alternator place to get rebuilt...the writing was on the wall. Put everything back together again. Alternator light came on when I started the car again, then did it's familiar "go out during high RPM" move. Yesterday, I threw a battery charger on my battery, because I've been driving the car a bit. I came back a 1/2 hour later because I had to go out. The battery charger said "full". Hmmmm...strange.

Today I drove the car around all day, and just for fun, when I got home, I threw the voltmeter back on the battery. When running...it showed 13.8 volts...just like it's supposed to.

But..as a possible related aside...I was just about to pull out of the mall today, and I noticed my left front headlight not working. I popped the trunk and jiggled the fuse that connects that corner....and the light came back on. I've also got a situation that my left front turn signal is ALWAYS on....solid. Like, it never blinks...just stays in the "on" position.

So, maybe I have a fuse block issue? Regulator's fine, alternator seems fine...what else could it be? What's the best way to recondition my fuse block? I've already cleaned it and sprayed a little WD 40 on there. Should I hit it with a 3M scrubbie pad or something?

Thanks for any advice!

mto