OK, for those who have been following my transmission thread, that's finally resolved. So I go for my test ride this afternoon, and my alternator doesn't bootstrap.

Background: There is a "bootstrap" process to the 914 alternators. Whereas new alternators have permanent magnets and begin creating energy immediately upon start, our 914 alternators do not start creating any significant voltage until the unit is "bootstrapped" by revving the engine to between 1500rpm to 2000rpm. Once this has been achieved, the magnets are energized and the alternator should work normally. Until the bootstrap has occurred, the generator really creates no significant voltage.

I had replaced my alternator with a used unit about 14 months ago. At that time I also replaced the voltage regulator with a new Bosch solid-state unit. And for the past 14 months, it has all worked exactly as expected.

As of today, the voltage gauge in my center console stays at about 10.5 volts. The battery voltage (pole to pole) shows 12.1 volts at rest, and after about a two mile test ride, it still showed 12.1 volts. I then started my car in the garage, reved the engine to about 2,500 RPM, and checked the battery pole voltage - still at 12.1 volts. I would expect to see 14 volts.

The only thing that has changed is that I have dropped and reinstalled the transmission several times. The ground strap is securely attached, and I have no difficulty in getting the engine to start. It is certainly a coincidence that my alternator problem is happening just as I re-install the transmission, and I don't believe in coincidences...

Any thoughts???

Does the generator light come on when you turn the key on? Does it go out when the engine is running???

you wiggled the field wire loose. =o)

is there a pool going on for the person who guesses right on this issue?

Clay; I am assuming the generator light is the same as the turn signal indicator (1974 2.0). When I turn the key to the "on" position, the Generator light blinks for about 1/2 second, then off. The engine starts and runs with no further generator light.

Please note that this light used to always be lit until I replaced an old turn signal relay (about 30 days ago).

Eric

No. The generator light should be in the left hand combo gauge next to a (G) sign.

http://www.914world.com/bbs2/index.php?showtopic=87424

Andy

If the generator light does not come on with the key on and the engine off, then your alternator will not charge. The light circuit provides the exciter voltage to the field circuit. I just recently worked on a 914 that had an LED bulb installed in the generator light circuit. It would not charge the batt until the light bulb was replaced.

Although I have a center console, the (G) light is located on my right-hand instrument display. No (G) light. As a matter of fact, in the 2 1/2 years since I've had this car, the (G) light has never been illuminated...

Eric

I liked your explanation about the bootstrap. Are you saying your fuel combo gauge is to the right of your tachometer? "G" should be on the combo gauge.

OK. I just went downstairs and switched the light bulb in the "Oil Warning" light with the "Generator" light. Now, my Generator light illuminates with the key in the "On" position. Once I start the engine, the generator light goes out. But I still don't get a voltage jump that would indicate the generator bootstrap is working correctly.



And I erred in a previous post. The Generator light is in the left of the three front gauge instrument combos.

Eric

Hi Clay,

I have the same problem. When I turn the key on the G-light is on & does not go off with the motor running. The volt gauge on the console needle is btwn. the 10 & 12 mark. What's going on???

BTW: I fired my new motor up today to break-in the new cam. It's running, but needs lots of adjustments. I was hoping to take it for a long ride. Oh well

Tom

It sounds like your alternator is working... Check the voltage at the battery with a DVOM. Bring the car to about 2K rpm, and you should have 13.5 volts.




If the alternator light doesn't go out, then the batt is not charging. May be the alt or the regulator.


For both of you.. you can try what is called a "full field" test. Take the regulator off the relay board, and feed 12v directly from the positive side of the battery to the field wire. With a DVOM connected to the battery, you should hear the alternator start whining and the DVOM should show about 18v. Don't do this too long, as it can burn up the alternator and the battery. IF it does work, you have a bad regulator.

DVOM at the battery - pole to pole:
All systems off: 12.3V
Start engine, Idle: 12.1V
2000 RPM for 5 seconds: 12.1V
3000 RPM for 5 seconds: 12.1V
Idle: 12.1V

Seems that the alternator is not energizing.

I will try your "Full Field Test" in the morning. If "no joy", I will remove the alternator tensioner bolt and rotate the alternator down to ensure the wires are all making contact.

When I was testing at 2000 and 3000 RPM, I noticed that the tach would randomly drop about 200 RPM then jump back up after a few seconds. The voices in my head say I'm missing something pretty basic. But the voices won't tell me anything else.

Anyway, thanks for your input and advice...

Eric

The light bulb in the G position of the instrument (AKA idiot light) is the key bootstrap element in the charging system. That bulb HAS to be the correct bulb for the car. The bulb allows a precise current to flow to the alternator windings to generate the initial magnetic field, and the bulb lights up when the current is flowing. Once the alternator starts generating power, the voltage that is developed opposes the battery voltage applied through the bulb. The light from the bulb should then dim and go out. If it only dims, then the alternator is not developing enough voltage; if it goes out, then the alternator is working properly.

The ground circuit for the alternator is through it's case, to the fan shroud, to the engine case, to the transmission case, through the ground strap, to the body under the rear trunk, to the ground stud behind the battery, and through the battery strap to the battery post. That is a lot of connections that have to work well.

The positive circuit is through a red wire to the solenoid on the starter, then through a heavy cable to the battery post. I see most alternator harnesses are very crappy at this point, and I have to rebuild every harness. (in fact most were crappy 20 years ago when removed).

Ok , you've had the tranny out a few times . You disconnect the starter wiring when this is done , there may be your problem.Check the wire coming from the alternator to the starter ( battery charge wire ) it may have a bad connection , come loose, maybe not installed , any combination of things. This is the only thing you have done to disturb the alternator .Worth a check.

Jaxdream

JAX; Thnks for the idea. It makes sense. Unfortunately, that wiring looks good.

So I finally pulled the alternator. When I turn it there's a slight grinding sound on one part of the revolution. So I figure the brushes are toast. I'm going to order a rebuilt unit right away. Anybody in SoCal got one, or should I get the FLAPS (~$55.00 + shipping) unit?

Question: I had replaced the voltage regulater about 14 months ago with a new Bosch solid state unit. Since it looks like the alternator went, should I automatically get a new VR, or should the protections within the solid-state VR circuitry have protected the existing unit?

My thanks.

Eric

Uh huh....that's the way it works

Eric has the fecal touch, what he touches turns to shit

What the doctor says it true. But I'm also not without luck. My tranny problem was quickly resolved locally. And my alternator problem ocurred within driving distance to my home.

To be honest, I've been living on borrowed time on the present alternator for the past year. The PO had installed a non-stock alternator which didn't properly fit, wasn't attached securely to the engine block, and failed on me 35 miles from home. Since it had neither the stock pully assembly or pivot assembly (which attaches the alternator to the block), I purchased an alternator for $5.00 off of eBay. The alternator was not guaranteed to work, but it had all of the fittings. So I thought I'd have it re-conditioned and install it. When it arrived I just bolted it in place and it worked!

So now that it appears to have failed, I really feel I got my money's worth out of the old alternator. I went ahead and ordered a reconditioned alternator which I will be picking up on Tuesday (YAY!)

The other thing to remember is that I really drove my 914 a lot this summer without doing a lot of maintenance. I usually schedule one weekend a month for maintenance, but between May of 2009 and August of 2009 I drove just about 7,500 miles with minimal maintenance (oil changes and valve adjustments). This included a couple of trips between Irvine, CA and San Luis Obispo (~250 miles each way). After all of that, when my 914 decides to develop problems, it does so within a few miles of home, near enough that I could easily drive home on my battery.

The good doctor kids me, but I don't think he knows how much I appreciate his assistance at the clinic, and how much his advice and assistance helped when I had the minor transmission glitch.

Best of luck, and please keep us updated on where you're going to be performing your residency.

Eric

Well then... here is a new avatar for him......


Click to view attachment

I really, really need that patch!!!

Eric

If you got a rebuilt alternator from Autozone / Carquest or other mass merchandizing outlets, check the length of the B+ stud. To long and it will arc to the rear cover wiping out your "rebuilt" alternator.

Thanks for the reminder.

I installed the new alternator and all is well.

My thanks to all for your advice.

Eric