Waiting on the side of the road for a flatbed to take me home.

Engine ran great. Charging system not so much. Driving along. Lights started going dim. Car started bucking. Only 5 miles to home but it wasn’t going to make it, and no shoulders to pull over safe on the little farm roads. So I pulled into a spot I knew of and shut it down and parked it and now I wait.

McMark had said earlier he wasn’t sure about the charging system. But the alt light was not on and no issues before now.

So. What’s the alternator I need to buy?
Maybe a new VR as well?
I guess I should test the battery and make sure it’s okay too.

Zach

That sucks, I know the feeling. Same thing happened to me Friday but with a broken CV joint. Good that you are close to home and hopefully an easy fix.

Did you check the generator light bulb? The wrong one will cause the alternator to fail to charge.

Bruce Stone is the man and has an alternator for me. Hopefully that is the issue and not a crapped out relay board or faulty wiring.

Zach

Seriously? The more I know about these cars the more I love them!

Very serious. The generator light provides the circuit to the alternator field. If the alternator is not charging, the light comes on because of the voltage differental between the alternator and the rest of the electrical system. When the alternator is charging, both sides of the bulb are "hot" so the light goes off.


That's why you can't use an LED in the generator light socket.

The alternator idiot light was on when you turned the key before starting right?
The light excites the field, so no light before starting and the alternator won't work.
Your alternator light not coming on once the charging system failed tells me something was wrong with the idiot light wiring circuit. That will also need to be fixed.

The two idiot lights are very important, I won't start my engines without them working correctly first.

Yup. Red light was on when I turned the key and went off when the engine started.

The light never turned on while I was driving. Just noticed the lights started getting dim about 10 miles into a 20 mile drive.

After I turned the car off on the side of the road, the alt light did not light when I tried to start the car again when the tow truck showed up. But the battery was really drained by then.

Zach

I hate the site of a pretty Porsche being dragged, this was my car at my dentist's office, the last place I wanted to spend any extra time.

Hopefully your car is something easy.

Click to view attachment

I probably would have made it home if I had not needed to use the headlights. But, I would not have noticed the problem were it not for the headlights dimming and assumed something was wrong with the EFI when the car eventually started bucking.

Zach

That is odd, as a preventative I'd still go through your grounds and connections at the combo gauge. Also make sure your battery posts, battery and trans ground straps, etc., are all clean and have good continuity.
Bad battery and ground connections can make your electrical system do wierd shite.

I had a bad ground on my Tacoma and the headlights would turn themselves on (dimly) and the warning buzzer would sound at about half volume. This would happen randomly. Guy I worked with said to check the grounds and he was right. Negative clamp on the battery was severely corroded so I replaced it and all has been fine for over a year now. Learned my lesson.

get an amp gauge.

Bummer, but you are so close man....glad you stuck with it.

rich

I wouldn't put in a new alternator until you know what is wrong with the charging system. Like Mark said, check all grounds and battery connections.

Charge the battery, remove the VR, short DF to D+ at the VR connector. This will put the alternator in maximum charge condition. Start the car and measure the battery voltage. If it is more than 15V, then the alternator is ok. Don't do this test too long as it applies maximum stress on the alternator and battery.

If you don't see 15V or so, the VR may be suspect.


I know the feeling of a Porsche riding on a flatbed. This ride from Pittsburgh to Allentown a couple of weeks ago cost me a cool $1000.

Click to view attachment

I had a VR that came unplugged while I was driving. No warning light, and no charging either. The light did stay off after I shut the engine off and turned the key back on again, though.

--DD

I also have rebuild tested relay boards should that be the problem. Done by 914Sixer, Mark Heard.

Ouch! If you drive older cars, AAA Platinum is a must have. My Jaguar got a free flatbed ride from Virginia to North of Philly about a year ago.

[/quote]

Ouch! If you drive older cars, AAA Platinum is a must have. My Jaguar got a free flatbed ride from Virginia to North of Philly about a year ago.
[/quote]

Yes, AAA is a must if you're driving an old car. Plus you save at hotels and stuff.

yup you ran out of juice, would check the belt tightness and then the voltage regulator, a new Bosch alternator is the final solution if the other two fail to 'rectify"

AAA Extended plan cost about $160 a years and well worth it. You get two tows per year up to 200 miles each . Did that after a 25 mile tow cost $125 with towing "insurance". But I see that is is closer to 300 miles from Pittsburgh to Allentown.

I have AAA gold so my tow was covered. As I gain confidence with the car and drive it further I’ll maybe up my service.

Did a test this morning with a spare VR I had.

Battery charged overnight.

With a newer VR (the one on the car last night when it failed) the Alternator light did not turn on when I put the key in.

With the old rusty “spare” the light lit up on key in, but did not turn off when the car started, even after I revved the engine.

Oh. And WHY AM I NOT WORKING ON A MONDAY you ask? Electrical storm last night took out power to the upper floors of my house (without tripping the breaker) at about 2:30 am; so now I’m waiting for the electrician to see what the damage is. At least 1/2 my House has power. :-/

I hope the house is ok. We had flooding in SE PA. Couldn’t pull out of the driveway the water was so deep this morning.

Just did Spokes test of shorting DF and D+.
Battery went from 12.12 volts engine off to 11.87 volts engine on at idle.

If I understand correctly even at idle I should expect to see greater then 12 volts with the VR shorted to Max Effort state. I’m guess the alternator is just dead.
Click to view attachment


I also made sure the belt was tight, and it was good and tight.
Going through grounds and don’t see anything too off kilter, though I have only looked at engine bay grounds as yet.

This alternator, by the way, only had about 300 miles on it. It failed really quick.

While I’m thinking about t, is there a way to bench test the voltage regulators?

Zach

I can’t find evidence of lightning having hit the house, but the crash last night was right on top of us.

I turned off the breaker for the suspected circuits so the house didn’t burn down and tried to go back to sleep.

When it rains it pours I suppose. Lol.

Zach.

I don't know man... sounds like the beginning of 'War of the Worlds'. If Tom Cruise runs by your house, you should run too! Just say'n lol

Electrician for the house will be here in a few minutes, but I've searched all the grounds from the cockpit back. Battery to body is pristine. Trans to body has no corrosion. Every place that grounds in the engine bay was tip-top. I need to look in the cockpit yet, but I suspect things will be good there too. The car is kept indoors and I don't have that many miles on the body since the restoration ended back in 2009/2010. If the ground that are exposed to the elements are good, I have to think the cockpit grounds will be good too.

Zach

A Bosch alternator is a B circuit alternator. That means that applying 12v to the field (DF) terminal on the alternator will make it provide maximum output, somewhere in the neighborhood of 15 to 18 volts. You should also hear the whine come from the alternator and an RPM drop on the motor.

Zach.. check and make sure the relay board is not the culprit. Pull the 3pin alternator plug off the relay board, and with the car running, apply 12v from the battery positive post to the DF terminal. If you don't get 15 to 18 volts and a whine, I would replace the alternator and the wiring harness to it. There is a group sale on the harnesses going on right now in another thread.

Buy a new Bosch alternator. A lot of the "rebuilt" alternators out there are just cleaned and maybe replace the brushes.

So was a battery charger plugged in and hooked up to your car when the lightning struck?

Yes, but the garage seems to have escaped unharmed.

Electrician is here now, and power is restored to the entire house. A bathroom GFI outlet died though and requires replacement.

Zach

I'll check it, though it will be after the electrician for the house leaves.

I bought the alternator and VR Bruce had. Its rebuilt but by a local guy that he trusts to do it right. If Bruce trusts it, so do I.

Zach

If you were close to me, I would give you one of the 8 known good alternators I have sitting on a shelf in my attic. They all have wiring harnesses and the metal air deflectors installed.

So, new alt, VR and harness are all on order.

Hopefully this weekend I'll be able to start putting on new parts.

I guess to fill the time I could start working on the front of the car. I have a headlight bushing kit my car desperately needs, as well as putting the surrounds back on.

Ass of the car is up in the air, so I could go and pull the tin and the old alternator too. Just get everything ready to go.

And I suppose I could start hooking up the cabin gauges again. You know, so I'd know next time when my charging system is about to take a dump on me.


Zach

Nothing to do with the car, but if your GFI plug going bad takes out the whole circuit, then it is wired in series.
The cheap way to wire a house is to wire it up in series. This takes less wiring and less time.
The proper way is to wire a circuit in parallel. A lot of electricians don't want to take the time to put pig tails on the plugs. They just wire up the plugs so the circuit goes through the plug. If a plug goes out, it takes out the whole circuit.

Greg W.

Check the ignition switch.

Tonight I put the new alternator, harness and VR in.
The red GEN light shone bright red at key in and turned off as soon as the engine started.

So that’s done, and initial results are promising.

At idle (about 1000 rpm) the battery was showing 12.89 volts (measured at the battery using a multi-meter) and RISING. I did not test amps. Is that about what I should expect to see from the alternator measuring voltage at the battery while at idle?

Haynes is saying 14 volts (mean) at 2200-6000 rpm, but I don’t know where they were measuring that. I guess I should test again tomorrow at a higher RPM. THATS what I get for looking at Haynes after I do the test.
Zach

12.89V at idle after the engine is warmed up or right after the engine started?

What is the voltage at higher revs?

Above 12.6V is good since the system is charging the battery. The voltage should be 13.5-14.0 at higher revs.

Right after the engine started.
I only ran the car long enough to start it and measure voltage. Car was on maybe 2 minutes tops.

Zach

It sounds ok so far. How many times did you rev the engine? That's when the alternator and VR will reach peak efficiency. As soon as you start the engine the battery has been weaken by the load of the start and the alternator+VR usually are running at low RPM during the start. A measurement at 2-3K after a minute or 2 warm up will let you know how the alternator+VR are working.

12.8-13.1 is good just after the start with low revs. Should increase to 13.25-14V when revving the engine.

System still isn’t charging right.
I drove the car to the gym, and then around. Maybe 7 miles. Pulled into the house and got the mutimeter out.
At idle I was showing 12.12 volts across the battery terminals.
Revving the car to 3k and I was showing 12.06 across the terminals. I should be seeing more at rev.

Grounds are good
Alternator, voltage regulator, and voltage harness are all replaced. Gen light is acting like it should.
I shorted D+ to DF and the engine loaded up and I saw 15 volts bear idle.

So what’s next?
Relay board?
New VR still suspect?

Zach

A fully charged car battery should be 12.6 volts so I would say that if you have less than that at idle you are running off the battery.

A normal working charging system should read 13.5-14 at idle.

Do you have a known good VR you can try?

Doesn't make sense that the board is bad if you can jump the VR leads and get it to charge.

Made sure you have the correct bulb (not a led ) in the gen lamp socket. Since
this bulb supply the voltage to make the generator work correctly a wrong bulb will
cause strange things to happen.

I know about the GEN light bootstrap. That light is correct.



I need to find the other two voltage regulators I have and test them. I hope I did not toss them away Saturday/Sunday while doing the alternator replacement.

I know its working better. Before when I did the D+ to DF test there was no load on the engine or anything. Changing the alternator HELPED but I don't think it fixed everything. And I'm concerned there is an underlying issue that killed the alternator. It may well be the VR.
Zach

I just got done running this issue down as well myself. While the Alt light would go out when I started the car and revved it, and it SEEMED like it was charging, it wasn't until I replaced my VR that I was able to get the alternator to start correctly charging the battery. I ended up getting a Hella replacement, which is a bit smaller, though it doesn't look like this

https://www.amazon.com/gp/product/B01LT7E5R...=UTF8&psc=1

Years ago when I thought my mechanical VR was going bad I replaced it with one similar to this:

https://www.ebay.com/itm/Auto-Tune-PT825-Vo...DkAAOSwUrdZdz~6


It is solid state and the electronics are potted. There is a short pigtail and the VR mounts where the screw for the mechanical VR mounts. I think they make an ajustable one as well.

Adjustable:

https://www.ebay.com/itm/NEW-ALTERNATOR-ADJ...9!US!-1


That one might be for a 6 cylinder?

I bought one of the solid state pig-tailed voltage regulators off Amazon. Costs a little more but will be at my door wednesday.

By sheer force of will, this will work. I don't want to buy a new relay board. I am worried though that I've now had 4 VRs for this car. I think they have all been the mechanical points type though, and I know mine was ancient. The one from McMark was newish, but may have been damaged by the failing alternator. I don't know what to say about the NOS mechanical one from Bruce.

And if this new one does not work, I've got to assume an issue with the relay board itself, and not the VRs fault at all.

Zach

Zach, This issue was the first ‘problem’ i experienced with my 914 soon after buying it in 2005. After all the tests, try several VRs, I put a WTB in the adds and Gerald sent one au gratis. [i was for ever committed to 914 world]. Try a different relay board.

Well, the new solid state VR did nothing.
I am forced to admit the issue MUST be with the board.



Though it is probably folly, I am going to attempt to rehab the board. I have a feeling this board has been the death of 2 alternators and probably other gremlins that have plagued me and McMark and the others who have helped withthis car over the years.

When I took the board off there was already evidence of a previous "repair" where someone had taken the potting off around the VR plug and soldered something down. I'm going to clear all the potting and start from new.

Because I'm stubborn. And I want to drive my car maybe this weekend.

Its frustrating as the car seems to be charging at idle. I had a meter on the battery for about 15 minutes and the battery went from 12.25 volts at start to 12.54 volts after a few minutes.

But as SOON as the engine revved to about 3000rpm, the battery fell to 12.01 and bounced around on the meter.

If I can't find an issue on the board by Friday, I'll suck it up and put up a post for a new board.
@spoke
Zach

With the engine running measure for voltage between the alternator body and the engine case if you measure any voltage you have a grounding problem with the alternator and the engine case with the bolts hold the alternator in place

While you have the relay board out, measure the resistance between the D+ to D+, DF to DF to Pin 2 of the cabin connector, and D- to D-.

You can see by the schematic below that the relay board doesn't do too much for the alternator except provide a place to mount the voltage regulator and provide a wire back to the dash for the GEN light.

You shouldn't be killing alternators that easily. Check all grounds and the transmission strap. When you had your engine out you didn't paint or powder coat the fan shroud? The alternator is grounded to the shroud and the only direct ground connection to the engine case are the 4 little studs attaching the shroud to the engine. The tin might also provide some grounding but it's really those little studs providing the most grounding.