Red Alternator Light On

Assuming the wiring is correct....Motor off check voltage at B+ on Alternator.  it should read 12  -  12.5V    Start motor rev it a bit ( light should go out) then idle, should read 13.8  + -  .    If you still show 12.3 v at Alternator when running, the Alternator is bad.

Thanks Al I've check it and I think the new alternator is bad it's what I was afraid of. Got it from Aircooled $299.95 I'll give them a call.

Pete

Well I contacted the alternator manufacturer PerTronix Inc. tech folks and they had customers with similar issues. He suggested I run a jumper from the alt. power terminal B+ to the smaller alt. terminal D to excite the alt. to charge mode. This worked the dash red light went out and the alt. was pushing 14 volts. I then turned off the power and did a restart check. Then the same thing happened the dash red light constant red and not charging until I hit the jumper again. Told the tech guy and he suggested it could be the bulb (amps/resistance not voltage since the bulb works). I tried another bulb and it's the same thing. So I think the alt. is ok and believe it could be a wire short issue. I just can't figure it out as I've checked and rechecked all grounds and connections. 

Any thoughts?

Thanks,

Pete

The dash light excites the alt to charge mode, the tech guy  elling you to use a jumper to excite the alt. is bs..  IMHO  I smell Snake Oil burning..send the over priced alt. back for a refund.

Redo your ground to chassis. I dealt with a similar issue for months before I redid my battery to chassis cable. Make sure you have clean bare metal to bare metal contact.

Thanks again Al, you may be right since the tech guy knew right away. The only weird thing is the original issue I had of my of my Bosh 55 amp alt. The dash warning red light coming on slowly during a recent drive then to full on red by the time I got home. 

So it does seem possible it's a bulb or wire issue. I did check and clean all the ground connections that i know of as Carey had first suggested. Front beam, rear battery, and rear trans to chassis. 

Thanks Bill,

I'll try a new ground wire to the chassis as well. All cleaned and sanded for contact. 

Pete

Random q-

are you using LED light bulbs in your gauge/alternator light?

i ask because when I changed mine over, I had to wire an exciter in parallel to the bulb, because the led bulb did not draw enough power to get the alternate or "excited".   See attached-   http://auto-hub.com/faqs/#exciter

if the buld is lighting up, you may have a (+) red or ground Connector issues in the gauge cabling .... This happened to me before I changed to LEDs ...from pulling In/ out the gauges a ground and a +red wires came loose... It was not visible, I literally had to re-crimp the various connections the cables had through the multiple gauges ( as Both cables are wired in series on my VS.) 

heres is a diagram that helped me-  before I made my own-  ( ignore my notes.... This is from my archives- when I was trying to sort out what wiring whent to what gauge connection-   before I had the 356 original gauges updated to match the cars wiring.

Hope this helps,

Thanks LFEPARDO,

No, I'm not using an LED there. That's a great idea on checking all + wires. I've checked all main grounds. I have read that you should not use LED's for this bulb. Good suggestions again. I'm at my wits end been at it a few days now pretty much trying everything. I may have to run a wire with a switch to a jumper on the alt. but I'd rather find the issue.

Thanks again,

Pete 

Let's isolate the alternator from the car wiring.

The alternator dash light is wired: 12v key on hot and the other lead goes to what is usually referred to as the " blue wire" and is designated as the "61" on the alternator which is ground for the dash light when the alternator is not turning . When the motor is running and a properly working alternator comes up to rpm (approx. 1,000 rpm) the alternator "disconnects" the ground and the rotating armature produces 13.8 volts hence the light goes off.

To test: Key off...Disconnect the 61 wire on the alternator that goes to the dash alt light this will isolate any wiring related to the alternator light within the car. With a test light attach the clip to a known ground and touch the B+ the light should come on confirming the test light functions.  Remove the light and connect a meter from the known ground to the B+ terminal to confirm your voltage,  it should read about 12 - 12.6 i.e. battery voltage.

Remover the meter and clip the test light clip  to B+, turn the key to on and touch the test light to the 61 terminal .... alternator ground, the test light should come on, this is replicating the dash light function.

Start the motor and see it the test light goes out or stays on . If it remains on, you have a faulty alternator, if it goes out your problem is in the car wiring. Also connect the meter back to ground and the B+ to confirm voltage,  a bad alternator will read about the same battery voltage as when you tested it with the motor off.  A good alternator will read about 13.8 volts.

Thanks again Al. Ok, tried all you suggested. One difference I have with your second to last paragraph is with the key on or off and touching the test light to the 61 terminal from B+ the test light comes on.  Should the test light only come on when the key is turned on?

Thanks Al,

Pete 

My error, no because you are getting 12v direct from the B+ which is battery 12v

Thanks Al. This is car-azy but I had an Auto-Hub exciter made for their Star LED's I got for my 356 that I didn't use so I figured what the hell I'd give that a try. I put it in and wow it works! For whatever reason now the dash warning light goes out and the alternator is charging up to 14 volts. It could be as LFEPARDO wrote maybe with all the fiddling around under the dash I bumped something and got things back in order or maybe the Auto-Hub exciter did the trick. It's all part of the Madness.

Thank you so much Al for guiding me through the system and helping out and thank you LFEPARDO for your suggestions too. 

Pete 

Here's the new Alternator, thanks again to the SOC guys above for helping solve my red warning light Madness.

Glad you got it sorted!