914-6 Gen light comes on when hooking up the battery. Options

[Porscheman912]

Ok, I have a friends 914-6 here, and just built the engine in it. Before doing the engine, and after, the Gen light comes on when the car is off. I took the starter, and Alt to a shop to have checked out, and they were both good. Replace the Volt reg with another new one I had, and still on. I have a wiring diagram, but does not show wire colors, or switches. The light would go out in 2nd position on the ignition switch, and then come back on. I dropped the fuse panel down, and now it is on in all positions. It goes out when started. I was getting a very light arc when I hooked the battery up, but when I unplug the alt plug from relay board it goes out. I am thinking it may be the ignition switch itself, and just wondering if anyone has seen this on these cars? It is an OEM 6, not a conversion. Any help would be great, I need to get the owner his car back, and I am still testing things, just trying to save time if someone else has seen this.

[914Mels]

Does the charging system work?

[Porscheman912]

Does the charging system work?

Yes, it charges, battery is at 12.8 volts. The light goes out when it is turned to the run position. It started with it on only in position 1 or off, and then in Position 3, run. It would go out in position 2, and when you start the car. I just did the engine break in, and it was charging, and after running for 20 minutes, it was at 12.9 volts after I removed the ground. I have a test light in series off of the - of the battery and it lights up bright when touched to the body or any thing else. I did find out the 4 ways do not work. I know the wire the runs from the voltage regulator goes to the 4 ways. I tried to remove the flasher and it is stuck. When I touched the test light, in series, to both sides of the Gen light plug, it comes on.

[Porscheman912]

The car only has 32k on it, and is original, other than the seats, which were updated.

[Porscheman912]

Ok I have tested everything I can. Broke out my 914-6 wiring harness, and what I have found, is the wire coming from th Volt Reg is hot, and when I checked the one on my Daily drive 914-4, the blue wire is not hot, but on the 6 it is. If I pull the 3 wire plug off of the relay board no short. I am not sure what is going on, and why the red wire on that plug is hot all of the time. Any help would be great.

[914Mels]

You may have a bad diode in the alternator. It's been years since I had a problem like this. If I remember correctly the car charged normal but the current backflowed through the diode and made the light come on. With the alternator unplugged, the light goes off, right?

[Porscheman912]

Yes, when I pull the three wire plug from the Alt to the relay board off, the light goes off. I checked all three wires when I had everything hooked up, and car off, and they were all hot. The guy who went through the alt had told me he found a bad diode, and replaced it, but I talked to 2 people who said the same thing you did. I have chased everything down on this, even fixed the 4 ways, which I found out had not worked in years, just so I could eliminate things, and it all came back to the alt. Thank you very much for your help, now the fun part is getting the alt out.

[underthetire]

You may have a bad diode in the alternator. It's been years since I had a problem like this. If I remember correctly the car charged normal but the current backflowed through the diode and made the light come on. With the alternator unplugged, the light goes off, right?

(IMG:style_emoticons/default/agree.gif)
And the flaps shows the alt as good, since it will output voltage.

[Ericv1]

You may have a bad diode in the alternator. It's been years since I had a problem like this. If I remember correctly the car charged normal but the current backflowed through the diode and made the light come on. With the alternator unplugged, the light goes off, right?

I agree. I had to replace my alternator earlier this year because of the same issue.

[Porscheman912]

Ok, I think you are right about the diode. Now that I have the alt out, I checked the wires, which tested good. Anyways, this morning, I grabbed another alt I made some jumper wires, and hooked up the alt. It was out of a 70 2.2 911, so everything had to be different. So, and electrical engineer friend of mine was out, and explained that even though the diode might test good, it could be bad under a load, due to leaking. He told me that it is like one way valve, electricity s suppose to flow one way out of it, and under a load, it may be leaking a just enough. I left the battery hooked up for 8 hours, and it dropped .8 volts. Thank you to you all for your help, I have never seen this before, but I will always remember it.

[914Mels]

Glad to help, I turned wrenches for 27 years before retiring so I've seen some very strange stuff on cars. Mike

[Porscheman912]

Ok, I just wanted to update this since I am finally finished with this car. Ok, the Original Alt was rebuilt 2 times, and gone through a 3rd. I feel bad for the shop that did it, because they have done all of my 356 starters, 911 starters and alts, and my 928 alt. This one was that odd, everything tests good, but dang thing kept kicking the Alt light on. I finally gave up, and ordered a new one. Well, as with the issuse that was going along with the alt, the new one was wrong. I tested it, in the car, and alt light was out. Went to install in fan housing, and bolts were to short. I started looking at it, and it was longer. I went into my loft, and dug around, because I knew I had a few alts that I had not seen in years. Well, sure enough, I had a new one. Tested that, and that fixed the problem.

The owner had told me the interior light would not work with the doors, so before hooking the battery up, I decided to see if I could fix it. Pulled the the switch out of the drivers side wires were there, pulled the one from pass side, and no wires. Reached up around the dash, and no wires. After looking at my 914-6 harness, and the wiring diagram, I found the wire for the pass side, plugged into the gauge lights. It was very melted. Anyways, I fixed that and the other electrical problems. I would almost bet money that the interior light ground wire being shorted, was a big cause of the alt going. I has to have a burnt wire in it. The diodes were replaced twice, and some other parts were, but it still kicks the alt light on. Now that everything is fixed, I wanted to share this with everyone.

No matter if it is new, tests good, and gets rebuilt, sometimes things just don't work. For everyone out there who reads this. I have been working on these cars for years, and it seems that the strangest things happen and they will drive you nuts. Just do your best, and keep checking, sometimes you just need outside advice just to make you realize this stuff does happen.

I just want to thank you all for helping, and I hope this may help someone else.