Electrical

Argeo · 08-12-2004, 05:12 AM

Ok, I have a electrical short somewhere on my 77 911 that sucks will suck the battery dead if i do not disconnect. Anyways I turned off the switch that is on the ground cable and then proceeded by hooking a voltometer between the negative post and the ground bolt and saw that the voltometer read 10v. Anyways I started pulling fuses looking for the the voltage to drop to zero. It never did so i thought maybe there are two shorts. I then pulled all the fuses front and rear and I still had voltage going across. My question is where do I go from here? Am I doing something wrong?

Thanks,

David

Porsche_monkey · 08-12-2004, 06:09 AM

So you have no ground cable connected but you measure 10V from the post to vehicle ground?

RoninLB · 08-12-2004, 06:16 AM

so what was the battery voltage to start with?

Argeo · 08-12-2004, 06:17 AM

Yes, I used the voltometer as the ground wire. I put the red on the ground body bolt and the black on the negative battery post. I removed all the relays I could find too, three in front and one in the back. I didn't actually remove the ground wire from the negative post, I turned it off using a switch on the negative post. I use it at night to keep the battery from draining.

I am trying but maybe i am doing something wrong here. Any suggestions would be helpful.

Not sure it means anything but when i put the blinkers on (with fuses in place), the indicator light (on dash) shows for both sides.

Thanks.

Argeo · 08-12-2004, 06:18 AM

10V, not good but before I replace the battery and ruin another I thought I would find the culprit.

Thanks guys.

Argeo · 08-12-2004, 06:19 AM

Should say 10v not running.

RoninLB · 08-12-2004, 06:22 AM

Quote:

Originally posted by Argeo

I am trying but maybe i am doing something wrong here. Any suggestions would be helpful.

ok.. I assume your interior light is off and trunk light is disconnected.

Do your routine and then turn on the interior light to see what's happening on the meter.

Argeo · 08-12-2004, 06:29 AM

Interior light and hood lights, they must only oput those on the good 911's. I dont have either. Under the hood I removed and inside hase never worked.

Anything else? Oh, I am at work working hard as usual. Was my method correct for trying to pin point the problem area. What doesn't use electrical?

Thanks again.

SC-targa · 08-12-2004, 06:32 AM

When the alternator diodes fail, they run down the battery. How many amps does this load draw? How long does it take to run down the battery?

Argeo · 08-12-2004, 06:45 AM

The alternator has about 5K on it but it was a rebuild. Hopefully I am giving the right volt. There are like a billion #'s on the thing. But I am certain that it reads the same post to post or post to ground bolt. I did that job years ago but I can not remember where the wire going to the alternator come from. One from the starter motor and then there were two others I think that run over to the wiring harness in the back. The battery, which was new last year was low on water when I went to fire up this past spring. Is that caused by overcharging. I only recently disconnected the extenal (it will come to me) voltage regulator, I guess the valeo alternator has an internal one. I also know that there was a extra wire that I was told to tape off and put to the side, the alternator didn't use it. Not sure how long it takes to kill the battery completelty meaning that I do not get any signs of electricity such as the alternator light when I first turn the key on, but it is probably a day or two. Is that alternator light suppose to turn on when I turn the key. It turns off after a second or two of running. Sorry, I am not to good with this stuff to be more descriptive but I am trying to describe what I do know.

Thanks.

Porsche_monkey · 06:55 AM

I guess you are down to removing wires and unplugging the alternator. I would be more inclined to reconnect the ground, use your meter as an ammeter and measure the current draw. Other than the clock I think it should be zero with the key out.

RoninLB · 08-12-2004, 06:54 AM

A millamp digital meter will give a clearer pic of what's happening.

Argeo · 08-12-2004, 06:56 AM

Can I unplug the alternator by removing the connector going to the permatune (I know), the connector in the engine compartments and the wire that feeds from the starter to the alternator. In that order.

Thanks.

RoninLB · 08-12-2004, 07:01 AM

Quote:

Originally posted by RoninLB

A millamp digital meter will give a clearer pic of what's happening.

how about a test light? but then the buld watt comes into play.

Argeo · 08-12-2004, 07:11 AM

I have a test light. I try disconnecting the alternator by the ways I have mentioned and see what happens. I hope it is not a bad alternator, though I think it had this problem when i bought the car. The battery was dead when i picked it up and I needed a new alternator, could be a bad wire someplace related to the alternator. Besides the starter, what else does not use a fuse. Oh, my clock hasn't worked either so that is draining nothing.

If I can not figure out, I'll give my cousin a call. "He's got an awesome set of tools". What movie is that from? He's an electronic guys who tinkers alot with cars so maybe he can diagnose if worse come to worse. If that fails, off to the shop. I'll never get all these gizmos working like clocks and compartment lights if I keep dishing out money for these things so hopefully I can figure out.

Thanks for your help everyone. Most helpful.

David

RoninLB · 08-12-2004, 07:24 AM

Quote:

Originally posted by Argeo
I Besides the starter, what else does not use a fuse.

- a dirty headlight sw could leak
- a dirty ignition sw could leak to the CD, etc.

Argeo · 08-12-2004, 07:26 AM

Sorry Ronin, what is SW?

Porsche_monkey · 08-12-2004, 07:27 AM

Switch.

Argeo · 08-12-2004, 07:31 AM

My stupidity scares me sometimes. Oh I hope my kids get my wife's brain. Thanks again.

jstobo · 08-12-2004, 07:42 AM

You can't use the voltage scale to find a drain you must use the milliamp scale. Hook in series at the plus side of battery and measure the current drain if any. Voltage means nothing. You always have voltage across the battery if it is hooked up. All you are doing, unless i misunderstand the way you are hooking up the voltmeter, is replacing the ground cable with your meter.