Alternator / VR Problem?

[911gilley]

Hi all. I'm still working through some problems on my '83 SC project car (the list is getting shorter, though with lots of great help from this Board).

I've been looking through the posts and cannot find a problem like mine.

I have a really strange issue with charging/not charging. Initially, the battery would die intermittently and need to be charged. I replaced battery with new optima-type and it seemed to correct the problem for a short time. But this battery too began to require re-charging. So I decided to check the charge rate at the battery with a voltmeter. It was intermittent...in other words, sometimes there was approx 14 volts and other times there was only 11. I never see the battery/alternator light come on, even in the low-voltage state; however, it does come on with ignition in "on" position before starting car.

So I decided to replace the alternator. I removed the old unit (a Valeo with datestamp of 1995 that looked like brand-new) and purchased a rebuilt Beck/Arnley unit from my local foreign auto parts store. I cleaned all connectors on end of wires where they hook onto alternator to shiny metal. Checked wire condition and braided ground to engine case and all looked fine. Installed rebuilt alternator, fully charged the battery, and started car. Measured voltage at battery again with car runnning at idle and watched it drop from around 12.8 (same as with ignition off) to 12 then to 11.8 over about 10 minutes......NOT CHARGING. I revved the engine to 5K RPM and all of a sudden I began seeing charge (~14.2 V). I shut car off after several minutes of charging, let is sit for a while, and restart only to have the same problem. Even with driving it, sometimes it is charging and sometimes not (I can usually gauge this by working the power window....if it is real slow I know that the alt is not charging at that time). It does seem like the revving somtimes causes the alternator to "kick-in" and start charging.

I'm going crazy with this. Can anyone point me in the right direction?

[bigchillcar]

hmm...with a new battery and alternator, that doesn't leave much but the VR. if it isn't regulating properly between about 13.5 - 14.5 volts all the time when running, it could be either under or overcharging your battery. either condition will kill a battery. i'd try the new VR at this point.
ryan

[911gilley]

I didn't mention it, but the rebuilt came with another VR. It did not look like a new one, though.
Is it possible that it is also bad?

Also, is it possible that the starter solenoid (where the alternator red wire and battery wire are "coupled") might have something to do with it?

Another thought is that there is a problem with the alternator "light" in the oil temp/pressure gauge. I did see in another post where this is needed to "excite" the VR.....since mine does not light except when engine not running and key on, could this cause the problem?

[304065]

Ed,

Check this thread, this person has the opposite problem:
Quick Alternator Question...

Remember from that thread I said there are three current paths. Well, your problem is that you have a working light, which is causing excitation of the alternator field, and the alternator is producing output, which is balancing the current from the battery, extinguishing the light. Yet your battery is not getting current. This narrows it down to the fat red wire from the alternator to the starter, and the very fat black wire from the starter forward to the battery.

Start with the battery contact, clean it, and the ground, with one of those battery terminal cleaners with the wire brush. Also clean where the ground strap bolts to the body. Now, you need to check and clean the connection on the starter. To do this, you must jack and support the car and remove the right rear wheel. Please be SURE the car is well supported, every year somebody gets killed when their car falls on them. Also, make sure the battery is disconnected, you don't want to weld the cable to the body sheemetal inadvertently. Unbolt the battery cable from the starter and clean the connections thoroughly. For most people, this is one of the greasiest areas of the car, be prepared for a dirty job.

You said you already cleaned the B+ terminal where it attaches to the starter. Are you certain you got it on the right terminal? Fat red to B+.

Good luck! Keep us posted.

[911gilley]

Thanx guys. I will clean the contacts that John mentioned to try to R/O the VR. I am sure that I got the connections right on the alternator (I always write them down before I disconnect). In reading that post, It has me wondering about a few things.

1.) I have a starter relay hooked up to the starter solenoid (the PO installed it). I did unhook it initially after rebuilding engine, but hooked it back up recently when having warm-start problems with starter not turning. Could I have hooked it up wrong? Could it be faulty? I do not have instructions for it (IF anyone has instructions for it can they post them so I can double-check connections; it looks like the one our host sells?).

2.) Could blue D61 wire be shorted somewhere causing non-excitation of the VR except at high revs (sometimes). Car did have all gauges removed during restoration. But why doesn't the light go on when I do not see charging at the battery (monitoring with digital Voltmeter).....mystery?

[304065]

Ed:

WRT Problem #1, I am not a big fan of anything other than the original Porsche design. If the starter needs a rebuild because the solenoid is sticking, then that's probably the right course to follow.

You turn the ignition switch. Current flows out of the battery into the switch, through the switch and back into the starter solenoid.

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part1-1.jpg

The starter solenoid energizes, which pulls the starter pinion into contact with the flywheel ring gear and starts the starter motor running at the same time. Engine starts, you release ignition, solenoid de-energizes, pinion snaps back away from ring gear, motor stops.

Question #2.

Remember that it's all about the bulb. If the blue wire were shorted anywhere on the engine side of the bulb holder, the bulb would glow continuously, and the alternator would not charge. If it were grounded on the battery side of the bulb holder, you would have an electrical fire.

Terminology: it's the FIELD that gets excited, not the Voltage Regulator. The current flows through the bulb, back through the 14-pin connector and over to the voltage regulator, which in your case is internal to the alternator. The regulator shorts the field to ground and current flows from the blue wire through the field to ground, inducing a current in the rotor. This, in turn, induces a current in the stator, which is rectified by the main diodes and also by the "trio" diodes, which feed the output voltage back to the blue wire. The blue wire now has power on BOTH ends, one end coming from the battery, the other end coming from the trio diodes. Since "voltage" is defined as electrical potential difference, and there is no difference in electrical "pressure" from either side of the bulb, current no longer flows and the bulb goes out.

So you see, you know you have a working light because it comes on when the key is off. You know the alternator is charging because the light goes out when the alternator spins up. But you don't measure higher voltage at the battery, which means that current isn't getting to the battery. Therefore, bad cable.

[911gilley]

Makes sense. I'll check the things mentioned earlier and post back.
Thanx

[911gilley]

UPDATE:
I checked the connections as mentioned and all seemed fine. I decided to pull out the alt warning light from the gauge only to find it did not have the correct wires running to it, but wires for the oil warning light. So I looked at the bulb in the oil warning light gauge opening and whola.....it had what seem to be proper wires: MY ALT LIGHT WAS ACTUALLY IN THE OIL LIGHT hole and vise-versa.

So, my alt light is NOT coming on with the ignition in the on position, or coming on at all, it was my OIL light. They are now in the correct holes in the gauge.

I looked at the alt light and it has three sets of wires attached to the bulb holder:

red/black and red/black on one set of terminals
blue/green and blue/red on the second
black/red and red/black on the third

So this is different from the 1982 SC wiring diagram that I have been looking at. I then look at charging system wiring diagram for a 1986 and I see that the red/blue wire goes to an alarm module......so does a "blue" wire, and they are bridged within the alarm module....WHICH WAS REMOVED FROM THE CAR during restoration several months ago (it resided behind the fresh air blower motor under the cowl)!!

I look behind the oil pres/temp gauge and see a 2-wire bundle with a blue wire, as well as a blue/red wire. I think this bundle runs to the alarm module and will check out tomorrow. There is a single inline spade connector splicing the blue wire before the 2-wire bundle, and this blue wire looks to originate from a larger bundle coming from the direction of the speedo ( I think this must be the blue 61 wire coming from the alternator). I think if I disconnect the red/blue wire from the alt light (which I am assuming is simply going to the empty plug for the alarm module and causing an open circuit for the alt light), disconnect the blue wire from the spade connector and connect it to the alt light, it will work.

If I am assuming correctly, this is the reason that my voltage regulator is not working......there is no signal voltage to or from it. Does this make sense?

Anyone have a wiring diagram for an '83 SC that shows the alarm module circuit? I'm not sure what the blue/green wire on the bulb holder is for.......it could be the oxygen sensor warning light lead?

[911gilley]

This tech article on our Host's site now really makes a lot of sense as to what my problem may be:
http://www.pelicanparts.com/techarticles/914_alternator_troubleshoot/914_alternator_troubleshoot.htm

[304065]

Good progress!

As you have discovered, the blue wire is critical.

Early cars have a red wire with black stripe (denoted as red/black) going to one side of the bulb holder, and the blue wire coming out the other side. I've never seen the three-terminal bulb holder, maybe it's an SC thing.

Good luck, can you post a picture of the wires or back of gauge?

[911gilley]

UPDATE#2:
BINGO! I pulled the blue wire from it's connector at the top of the 2-wire harness mentioned earlier, and took the side that looked like it was coming from the alternator (out of the larger wiring bundle and it has the female spade connector) I disconnected the blue/red wire from the bulb holder and simply connected this wire in its place. Immediately got an alternator light on with ignition, and off with engine running......take voltage measurement at battery and 13.8 to 14.28 volts! PROBLEM SOLVED!

Apparently, the '83 SC with an alarm has this setup....the blue wire from D61 alternator runs directly to the alarm module behind the blower motor under the cowl. From here it jumps through the module (there are 2 "61" spades marked on the alarm unit where the connector snaps on) and then back out via a blue/red wire to the alternator light. I simply bypassed this circuit by pulling the blue wire before it heads to the alarm unit (and conveniently had a factory M/F spade connector inline right behind the oil pressure/temp gauge) and replacing the blue/red wire on the alt light with it. This circuit does not show the red/blue wire or alarm unit on the '82 SC wiring flow chart, so this must be on the '83 flow chart which I do not have. I found it on the '86 wiring diagram.

Who would have thought that it would have been something this simple? Well, at least I have a new alternator in the car now, even though, in hindsight, the old one is probably still good (glad I kept the core).

Seems like this is not a common problem (the alarm circuit part) with alternator troubleshooting, as I did not see it come up anywhere in searching the threads eariler.

THANKS John and everyone else who replied to this thread and put me on the right track. Simply another tribute to the great bunch of people on this Board.

I'll try to get a picture of the back of gauge to post also.

[304065]

Nice job Ed.

Electrical problems can be mystifying, but on the earlier cars they are pretty simple to resolve.

My old 964 had no fewer than Forty-Eight electrical motors on board. In 20 years, I wonder if it will be as easy to diagnose as an '83 SC?

Congrats on "de-mystifying" the electrical system.