Alt volts

[BillGrissom]

I think 0.6 V loss from BATT+ to the upstream side of the ballast is not bad. Your ignition system would probably still work with as little as 8 V at the ballast, though a weaker spark. The drops are in the wiring, bulkhead connector, key switch, bulkhead connector again and spade lugs.

In my 65 Dart, I installed an underhood power distribution box from a Grand Cherokee, so my ignition path is straight off the battery via a relay, as 67Dart273 suggests. I also got rid of the original Mopar relays (starter, horn) and have relays for headlights.

 

[Otateral]

Had some trouble today. Car wouldn't start, so got a jump. Got a new battery (was a really old battery anyway, so figured it was time). When I got home, I decided to grab my multimeter and check things. With the car on, I've got only 12 volts on the new battery. Decided to check the alternator and I've got 20volts!

Checked the voltage regulator and it's within its usual range. I'm thinking the alternator must have gone bad and is overcharging, and that it most likely blew the fusible link, which is what caused the dead battery to begin with.

This sound right?

 

[67Dart273]

You have 20 V at the alternator and only 12 at the battery?

This is a SURE indication of the typical trouble with the charging line/ ammeter circuit.

Your top suspects are:

Bad terminals in the bulkhead connector

Broken terminals at the ammeter or trouble in the ammeter itself.

Broken connection right in the molded wire end at the alternator output terminal

READ (please) this excellent article from the MAD site on the hows' and whys' of this problem:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Even if you do not perform this bypass, this article is an excellent read. Scroll down the page and examine the simplified diagram.

 

[C130 Chief]

If the fusible link is blown, it will be pretty obvious, they burn to nothing REAL QUICK! But, if your alternator is producing 20V (about max for an unregulated alt) and the battery is only at 12V, something is WRONG!!! What is the voltage at the alternator with the engine off? (should be the same as battery).

My guess is the primary charging wire (10 AWG) that runs from alternator through bulkhead connector to the ammeter back through the bulkhead connector to the starter relay has an open circuit somewhere. Sure, a burnt fusible link would cause this, but so would a fried bulkhead connector or dead ammeter.

If you ran a 10 AWG wire from the alternator directly to the positive battery cable the ammeter in the dash wouldn't do much any more, but I bet the battery would charge.

 

[BillGrissom]

Your relay drawing is almost right. The blue wire (ign1) goes to coil+ (86?), but coil- (85?) must be grounded (you don't). Check the back of the Radio Shack package since the coil polarity matters if there is a diode across the coil. I run +12 V supply to the sideways pin (30). The output to your voltage regulator is pin 87. Some relays have a pin 87a with is "normally closed" if you need something to open when the coil energizes.

The reason you need a relay is because if you hooked Vreg sense directly to the battery, it would draw some current with the ignition off and could run down your battery. Of course, new cars have many loads on the battery when off, which is why airport parking lots regularly jump people who left their new car >2 weeks.

 

[Otateral]

Chief was correct, except that the problem wasn't at the bulkhead. I did the MAD bypass a while ago, and my shotty soldering is to blame. Turned out the circuit had an open spot. Since the vreg was telling the alternator that the battery was low, the alternator would increase its output but to no avail.

Sadly, the alternator seems to have cooked itself. After I fixed the bad connection, the alternator pretty much wasn't doing anything at all. Only 12.4 volts output when hooked up to the battery. I picked up a new alternator and got 14.7v at the alt, 14.5 at the battery. That's as good as I've ever had it.