The 4 wire thing-a-ma-bob for the alternator... ! NEW QUESTION !

[Greg72]

So.....

I had this brilliant idea to finally move the '72K5 into the ManSpace tonight.

Got everything cleaned up really nice in the garage, and put a fresh battery in the truck to get it started. Pulled it from the side yard onto the driveway, and decided to give her a quick rinse with the hose to wash off the dust, spiders, etc.

Well something didn't go quite right.

As the engine was running, the hose shot over into the battery area (no inner fenderwells, remember?) and in an instant the engine completely DIES! Not like a stumble, just flat out dies INSTANTLY. Tried re-cranking it, but it doesn't seem to have any spark....I can definitely smell fuel after cranking a while. Definitely seems electrical.

Two immediate things I notice:

1. Small molded fuse holder (original) from battery. Pull it apart to check the glass fuse inside....all corroded. Cut it out and spliced the wire together with a promise to replace the fuse later. Still won't start.

2. The opposite side near the core support has a small 4-wire plug which I think has to do with the alternator charging wires (blue / white) and a couple others (Replaces the 4 original regulator connections). Pull the cover off that one, and it's all green and corroded, the two center connectors break off. I tried to jam some thin metal in there to re-establish electrical connectivity, but the truck still won't start.


Pulled a tarp over the whole mess and left it blocking the whole driveway. I guess I'll have to deal with it some other time. There's NO way I can push it into the garage stall to repair it there....too much tire and not much air in them.

Any ideas besides replacing the obvious defective items above????

Guess it's time to get intimately familiar with the wiring schematic again....

 

[pauly383]

That box is the voltage regulator , you have the older wiring like my Chevelle originally did .

May as well be a good of time as ever to convert to a newer alternator , and clean up the wiring

 

[Greg72]

That box is the voltage regulator , you have the older wiring like my Chevelle originally did .

May as well be a good of time as ever to convert to a newer alternator , and clean up the wiring

Pauly,

Nope. I have a newer style alternator. This molded plug replaces the old regulator....it's sort of like a molded "cap" that plugs into the 4-wire connector that used to plug onto the regulator.

Does that make sense??

 

[Yukon Jack]

Can you get a picture? I'm having trouble understanding the location of the plug.

How does your fusable link from the battery to the junction box on the passenger fender look? I'm wondering if something shorted and the fusable link burned up. I've heard occasionally they will burn but still look ok.

 

[Greg72]

Here's the schematic showing (in RED) the two things I'm talking about.....the one in blue is the fuseable link, but I haven't verified that one yet.

The "Regulator" isn't there in my K5. It was replaced by a plastic cap with those 4 electrical connectors inside it (brown, red, white, dk blue)....presumably to bypass the function that the regulator used to do, since the alternator is internally regulated. What I don't know is if I can simply cut and connect certain wires together directly, or if there is some other "magic" going in inside that molded cap????

 

[Yukon Jack]

That is all that is happening inside that cap. There is a FAQ over at the 67-72chevytrucks.com site showing which wires need to be joined and/or terminated.

Here it is http://67-72chevytrucks.com/vboard/showthread.php?t=119379

 

[JDahl]

The Fuse you replaced was probably the one of the ammeter fuses.

 

[Greg72]

That is all that is happening inside that cap. There is a FAQ over at the 67-72chevytrucks.com site showing which wires need to be joined and/or terminated.

Here it is http://67-72chevytrucks.com/vboard/showthread.php?t=119379

YJ and others,

Now that I got the truck started again (bad MSD coil as it turns out), I am trying to resolve my other wiring issues.

I read that article and my alternator is a 3-wire deal (Heavy red wire to a post from the battery to the rear post), and a white and blue wire in a molex-style connector on the side of the alternator.

The instructions describe jumpering the brown and blue wires together and leaving the white wire disconnected completely. My question is: Do I need to run a small jumper for 12V from the rear post of the alternator to that white connector in the molex??? That's the only part I'm not 100% clear on after reading that other message thread.

Anyone know?

 

[bigblock72]

Usually the internal reg connector has a white wire and a red wire. The white wire on the connector connects to the brown wire in the truck harness and the red wire on the connector connects to the heavy red wire on the back on the alternator. If the alternator doesn't work properly swap the wires in the connector.

 

[Greg72]

BB72,

So one final dumb question....

If I go to a "1 wire alternator" at some point, what is it 1 wire that gets used? Is it only the heavy gauge charge wire that runs from the alternator to the battery???

It might be good to rip out all that nonsense wiring and old external regulator wiring....seeing how quickly corrosion forms in the engine compartment connectors, simpler is certainly better.

 

[bigblock72]

The one wire alternators use the wire that connects directly to the battery. They turn themselves on when they spin up fast enough (usually around 2,000 engine RPM). I don't really like the one wire alternators all that much as they can be somewhat flaky. I recommend sticking with an internal reg. alternator and put a little dielectric grease in the connector. Or you could even go to a newer style alternator that uses a sealed connector, they usually come in 80-100 amp versions.