Need Alternator Help

[Spud]

I guess this is what happens when you mess with something that was working, now its not.

Car is a 1971 911S. I took my fan/alt housing out for some fan beautification (had a poor paint job) and upon reinstalling everything and attaching the alternator wires back just as they were (I took notes!) I now have a continually glowing alternator warning light. The light glows withought the key in the ignition, goes out when the key is turned to the start position. It also seems as though my battery is draining, shows just 6.5V now, showed 10.5 yesterday.

I need help fast, the first time trial of the year is next weekend!

I believe this is an SEV/Marchall alt, there is little identification on the thing, but I did see a "SEV".

Thanks!

[tsuter]

Well the alternator used to be grounded through the housing to the motor and frame. Too much beautification paint on the housing and it may no longer be grounded.
That may be the easiest to check for starters.

[Spud]

I did not paint the housing, although the ground strap looks pretty beat up. The question becomes could this cause the light to glow continually, would be worth replacing? Also, I neglected to mention there was only 3 wires on the back of this alternator, does that tell me it is internally regulated?

[vash]

damn, just a few weeks ago there was a great thread about alts. it was started by sponge. here: At wits end... alternator...

if your light is on all the time without the ignition on. it gotta be the blue wire on the back of the alternator. look at the thread above. some smart folks jump in that one. look at john cramers' and loren's replies closely. i bet you have an easy fix.

[Spud]

Thanks for the link unfixed, I saw that one when I searched prior to posting. The problem I have is slightly different tho since my light is glowing all the time (key does not even have to be in the garage, let alone the ignition..)

Also I have now read in 2 different spots (Wayne's book and on this site) that "if your light glows with the ignition off your Alt is dead".

So just in case... does anyone have a reccomendation for a Alternator rebuilder in the Bay Area?

Keep the suggestions coming!

[vash]

mine may be suspect too. i get low voltage. i am going to send mine to LA. i asked about bay area guys, but i heard this place is good.
alternator replacement

but i have a few other issues to figure out before i can worry about electricity in my car

please let me know if you find a good one here local.

[Spud]

bumpity...

[Jim Sims]

For general alternator troubleshooting list see:

www.pelicanparts.com/914/914qa/914Q_electrical_alternator.htm

Jim

[Spud]

That was one of the two places I had read this:

"Alternator indicator lamp is on with key off.

Alternator has failed, and diodes have shorted out. Replace alternator and in the meantime, disconnect battery to prevent complete draining of the battery. "

Which has lead me to believe that my alternator is kaput. Just waiting to hear if there is any other circumstances that might make this happen (light on all the time).

Thanks again,

[304065]

Doug,

So in normal circumstances, here's what happens. Current flows out of the battery to the ignition switch, through the warning light bulb on the back of the oil pressure gauge, back through the blue wire to the voltage regulator, then over to the alternator D+/61 terminal, where it flows into the rotor and to ground. Usually, the reason it lights is because the voltage coming from the battery (which gets fed back into the rotor by the DF wire or directly to the rotor in an internally regulated setup) is less than the voltage being put out by the battery.

So consider what's happening when the ignition switch is OFF. The +12v connection is open, one side of the bulb, the one with the red and black wire going to it, is shorted to ground through the ignition switch.

OK, so we have a ground on one side of the bulb. Now we need power to the other side. It has to come in through the blue wire. The blue wire goes to the regulator and over to the alternator, where it connects to one of the brushes. The other brush is connected to ground. Also connected to the same brush is the DF or "dynamo field" wire. The DF wire comes from the voltage regulator, and once the alternator is producing current, the DF wire regulates the field strength, regulating the output voltage from the stator. So the DF wire gets its power from the stator.

When the diodes are working correctly, current is only supposed to flow in one direction- from the stator to the B+ terminal and down to the battery. When the diodes are defective, current flows from the Battery past the diodes, into the stator, and also to the DF wire, where it flows to the rotor, where it flows into the D+/61 wire, then down to the ignition switch, providing the "hot" side of the circuit!

Now, what kind of alternator do you have, internal or external regulator? If you want to post a picture here we can help.

Good luck!

[vash]

i love it when john cramer jumps into the alternator threads. i can feel the question mark floating over my head. but for the record, i did mention the blue wire previously.

cliff

thanks john. btw, i am cutting and pasting your answers on a word document. your and loren's, if he ever comes back.

[Spud]

Here is a pic of the rear of my Alternator. Its definately a Marchal, but I have no idea if its internal or external regulated. The only clue I have is that there appears to be a Marchal regulator mounted on the side panel in the engine compartment, however it has NO wires attached to it. Looks to me like someone "upgraded" to the internal requlated unit and just sniped the wires on the regulator.






As you can see there is only 4 wires behind the fan (one is ground strap).

What else do we need to know?

[johnsjmc]

Are you sure the red power wire shouldn't be connected to the RED terminal on the back of the alternator? The terminal may be marked B+

[304065]

New alternator not charging!

Does it look like the alternator in the thread above?

I think your connections are right. What you have there is pretty common, a Marchal that's been converted to an internal voltage regulator.

You still have the regulator over on the console, but it's no longer necessary now that you have converted. On a later car, you could simply remove it, but my recollection from a recent Warren (Early_S_Man, the board's ranking electrical guru) email is that the early cars didn't have a plug. Anyway, since you only have four wires (Red B+ pair, blue D+/61, brown ground (D-) and the ground to the engine case (the copper thing snaking around the airguide), somebody already took care of getting rid of the black DF wire along the way. Remove the regulator following Warren's guidance here:

voltage regulator removal

EDIT. I see that the reg has no wires going to it. Interesting. OK, for fun, what happens when you touch the blue wire to the engine case when the ignition is on? The warning lamp should come on. If it does, then your wires are correct. If not, new branch to the problem-solving flowchart.

I went to an internally regulated Carrera (1260 watt) alternator, ditched the VR (I ran the wires directly to the 14-pin connectors) and WISH I NEVER HAD. On the race track, when it's hot, heat-soak from the engine heats up the internal VR, which is right next to the case! You have to cut the airguide to do this to an early car, which ends up exposing the VR with NO insulation, the case is 2" away! Anyway, the practical effect is when it gets hot, the VR shuts down and the low voltage light goes on, followed by me cutting the engine and coasting into the pits! Now THAT sucks.

Good luck!

[Spud]

Ok John, I hooked the battery (-) back to the chassis and touched the blue wire to the engine (with the key on) and we have a red light.

So if (big if) I follow all of your other teachings on other threads this tells me that my Alternator is grounding due to diode failure? Which also tells me its my fault since it was working (somewhat, light glowed most of the time...) before I started monkeying with the fan assembly.

I guess its rebuild time?

edit: mine does look exactly like the one in the other thread you sent me to, that the guy bought from Pelican (pitty they don't sell them anymore...)

[Spud]

bumpity..

[Spud]

For any SF bay area pelicans I have been refered to a local (Campbell) company specializing in Alternator rebuilding. Their info is as follows:

Autoelectrics
1360 White Oaks Road #D
Campbell, CA 95008
(408) 559-3540

THey are a block or so from Ken's Sportech in Campbell.

Don't know what it will cost yet but I took my Marchal to them this morning and they knew exactly what it was from and have the parts on had to repair it. They also mentioned that they have rebuilt Marchal's on the shelf ready to go (external Regulators only). The best part? Promissed me it will be done this afternoon

I will get this puppy back in the car tonite and report if this indeed solved my problems!

Thanks for everyone's input!

[304065]

Good luck, keep us posted.

Probably a good idea to charge the battery overnight before you try it out.

[Spud]

I gathered that charging the battery was important, so it went on the charger first thing this morning

Thanks again!

[vash]

damn spud, i shoulda come to give you a visit and a hand this weekend. if you are still into next weekend, or thursday (holiday) let me know. i think it would help to have two people. i tend to run around the car alot troubleshooting, two would save some footwork.

cliff