malo68

Need help please. I have an '82 that I bought recently and just got running. The back of the old alternator had a broken stud for the positive cable on the back so I replaced it. I bought a new Delco alternator, hooked it up, tested it with my voltage tester and with engine running, I am getting only 11.8 v coming from the heavy red wire on the back. I am also getting the same reading at the battery. I thought the alternator may be bad so I took it back to the parts store. They put it through 4 different tests on their own machine and it tested good for all of them, showing an output of 14.5V. I put it back in my car and I'm bak to 11.5 from the back of the alt. W/engine running again and a dimly lit battery light on the gauge panel while it's running. Need to get this car charging. What could be wrong? Any advice would be appreciated. Thanks, George

wombvette

Check the voltage on the two wires that plug into the alternator.

lionelhutz

Check that you have battery voltage on terminal 2 of the plug. It gets the power to run the regulator and power the field from that terminal.

malo68

Terminal 1 (brown wire) I'm getting approx, 4.82 volts
Terminal 2 (red wire) no reading.
Should there be 12v getting there? If so from where?

lionelhutz

Yes, terminal 2 should have 12V. I don't have a wiring diagram but my first guess would be that it connects to the horn relay.

malo68

Thank you. I know that there's a relay next to the wiper motor on the firewall driver's side. I know mine is bad because I swiched it with the one in the rear compartment to get the fuel pump working. Not sure what it was powering. Could it be this? Will check diagram. Thanks again!

malo68

I think I made a boo boo. I tried to trace the red wire from terminal 2 back but it seems that it goes right into the harness through the firewall that leads to the backside of the fuse panel. So I thought I would just run a new wire from the unlabeled tab (that gets power with key "on") on the lower left hand side of the fuse panel (left of lower injector fuse) to terminal 2...and I got power (14.5-14.6v) from the output wire with engine running. Hurray! My first ride in it!... but wait...

I got in, took it for a ride around the block, got it in the driveway then saw battery light on in console. I checked again and it's back to 12v, no power to terminal 2 again, and no power from that tab in the fuse panel that the other end of the wire went to. How do I get power back to terminal 2??? This is aggravating! I want to move on (but it was nice to drive it for the first time)

ctuinstra

Here is a great article to read about the wires going to the alternator. Also you should check the output above idle to see if it changes.

Some alternators require a field excite (12v) to turn on the windings. That should be on the left side as viewed from the rear of alt.

http://bob_skelly.home.comcast.net/~...ternator1.html

ctuinstra

Terminal #2 is the voltage sense. It is an input for the alternator to "sense" or detect that actual voltage at the battery or some other place way downstream of the alternator. You could, temporarily, connect #2 to the output of the alternator to fool it so it "senses" proper voltage all the time.

But more of your issue is with terminal #1. 4.82V is all wrong. You need to find out why you not getting 12v. This should come from the ignition.

lionelhutz

No, it's not. Terminal #1 is fine. The problem is still terminal #2 missing the 12V.

malo68

Thank you ctuinstra for that link to the article and lionelhutz for your input...interesting alt. article. So after reading that, I'm thinking the most logical place to power terminal 2 would be from the junction block in the battery compartment. Still a mystery to me where the power was coming in from before it became powerless. Am I missing a blown fusible link somewhere? Is there so kind of diagram that shows where all of them are located on an '82? The wire diagram show them but locations are inaccurate.

Also, let's say I do run a new wire. Since it's a constant 12v source, is that ok for the hood light which will also be powered by it since the wires are connected. Will it shut off??

gungatim

you can run a new terminal 2 wire straight to the battery. Read the article posted above.

hugie82

Ah, this might be painfully obvious but did you rev the engine???
Many alternators today self excite and you have to rev the engine over 2000-2500 rpm to get them to turn on.

SH-60B

Clean the grounds from motor to frame and from battery to frame. Voltage to the dash lite must be the same om both sides for lite to go out and energize the alternator

lionelhutz

You found the wire going inside the cabin. From what I can tell on the schematic, the wire just loops back to the firewall plug and connects to a red wire with a black stripe which then goes out to what appears to be a terminal block. the terminal block is where the main wires from the starter solenoid, alternator stud and another red wire that also goes to the firewall connector are all joined.