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Mon Nov 16, 2009 10:24 am

Car wasn't starting, we jumped it, pulled the cables off, put the volt meter on the battery and it is at 12 and slowly declining till the car dies

We get a new alternator, it is doing the same thing

We disconnected the alternator wire to the battery and started the car, and tested from the b+ post on the alternator, and it is showing 4 volts, it never goes past it

Did we just slave to put in a bad alternator? Sad Is there somewhere else I should be looking?

This is a 1970 bug upgraded to 12 volt

Mon Nov 16, 2009 10:34 am

internal or external alternator? both need the generator/alternator warning light working to work. i run a wire from the B+ terminal on the alternator to the starter to reduce the path back to the battery.

here is a diagram to show how i wire them.

Mon Nov 16, 2009 11:27 am

I have the speedo out of my car, and I never notice these lights light up when I turn on the key, do I have to have the speedo in to complete the ground or something? :?

Mon Nov 16, 2009 11:50 am

OMG, if it is the speedo being out of the car that caused this.. I can't believe it! :x

Mon Nov 16, 2009 1:04 pm

it is definitly the speedo. becareful you can short out a altenator qiuck by doing that. i know from expierence. lesson learned.

Mon Nov 16, 2009 1:07 pm

ibjames wrote: OMG, if it is the speedo being out of the car that caused this.. I can't believe it! :x the speedo completes the intire wiring circuit. :D

Mon Nov 16, 2009 2:49 pm

bugzz1 wrote: ibjames wrote: OMG, if it is the speedo being out of the car that caused this.. I can't believe it! :x the speedo completes the intire wiring circuit. :D

if you just want to test it if you still need your speedo is out. you can run a small 12-14 volt (non LED) light from a 12 volt source to the D+ terminal. the light should come on when the car is off and go out after starting the engine. D+ is a ground before the engine is started but changes polarity after starting.

Mon Nov 16, 2009 3:38 pm

I am having the same issue, but my speedo is in. Car has been running fine, then the generator light started staying on. Then Saturday, I started it to test it and after a few seconds, the light went out (bulb not blown). I thought a piece of something got somewhere and it's then it was gone. Today, I go to move the car and it's back on (even when revving the engine). I do have an external voltage regulator(?) and it has a small red wire with a fuse that was blown, thought that was it, replaced fuse, light still on. Not sure where to check or how to check. Checked posts on generator (red and green) but had pulsing 2-3 volts on DC and pulsing 4-5 volts on AC while idling. Not sure where to look or what to look for.

Mon Nov 16, 2009 4:14 pm

an alternator should be doing 14 when idling no?

Mon Nov 16, 2009 5:15 pm

ibjames wrote: an alternator should be doing 14 when idling no?

around 14 volts is the normal.

Mon Nov 16, 2009 5:19 pm

pafree wrote: ibjames wrote: an alternator should be doing 14 when idling no?

around 14 volts is the normal.

Is that checking off of B+ and D+ or B+ and a grounding point??

Mon Nov 16, 2009 6:02 pm

friedshrimp wrote: pafree wrote: ibjames wrote: an alternator should be doing 14 when idling no?

around 14 volts is the normal.

Is that checking off of B+ and D+ or B+ and a grounding point??

B+ and at the battery

Tue Nov 17, 2009 12:34 pm

yep, that was the problem.. put the speedo in and I'm getting 14.. thanks a lot guys! Who would have thought! :!: :?: :!: :?: :?

Tue Nov 17, 2009 12:37 pm

ibjames wrote: yep, that was the problem.. put the speedo in and I'm getting 14.. thanks a lot guys! Who would have thought! :!: :?: :!: :?: :? alright :D now drive the shit out of it, like you stole it. :twisted:

Wed Nov 18, 2009 11:32 am

pafree wrote: friedshrimp wrote: pafree wrote: ibjames wrote: an alternator should be doing 14 when idling no?

around 14 volts is the normal.

Is that checking off of B+ and D+ or B+ and a grounding point??

B+ and at the battery

I'll assume you mean the negative terminal of the battery.

Of course, wouldn't going to the chassis be the same thing?

Wed Nov 18, 2009 11:49 am

friedshrimp wrote: pafree wrote: friedshrimp wrote: pafree wrote: ibjames wrote: an alternator should be doing 14 when idling no?

around 14 volts is the normal.

Is that checking off of B+ and D+ or B+ and a grounding point??

B+ and at the battery

I'll assume you mean the negative terminal of the battery.

Of course, wouldn't going to the chassis be the same thing?

sorry for not being clearer, he was checking the see if the alternator was working. you can check at the B+ terminal on the alternator and the positive terminal on the battery to see if the voltage is making its way back to the battery. you are correct that the negative probe on the voltmeter can be on either the negative side of the battery or the chassis that is grounded.