Instant loss of charging... car is now dead on road...

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Be careful reading resistance (ohms) with the battery hooked up, better yet, don't do it

Older multimeters can be fried applying power to the ohmeter, newer digi meters are usually protected, but with power on part of the circuit, you don't get meaningful readings.

The 28V on the alternator stud indicates that the alternator is trying to charge but that IT IS NOT hooked to the battery.

Pull your bulkhead connector apart and inspect it. Probably right in there. A quick fix is to run a second wire, a big one, no 10 or no6 direct from the alternator stud to the battery stud on the starter relay.

If you don't have that big wire, 3 no 12's or 2 no 10's in parallel will work.

Go back up and read the MAD article. You have a break in the charging path somewhere.

Also the low voltage you are getting on the "IGN run" lead shows two things:

With engine off, it shows you have voltage drop in the harness, the path from the battery to the ignition feed. This will cause overcharging

With engine running, the low voltage at that point shows it's not charging.
 
67Dart273 said:
Be careful reading resistance (ohms) with the battery hooked up, better yet, don't do it

Older multimeters can be fried applying power to the ohmeter, newer digi meters are usually protected, but with power on part of the circuit, you don't get meaningful readings. mine is resisted but good to know
The 28V on the alternator stud indicates that the alternator is trying to charge but that IT IS NOT hooked to the battery.

explains why i try to remove the cables from the battery while running it just dies

Pull your bulkhead connector apart and inspect it. Probably right in there. A quick fix is to run a second wire, a big one, no 10 or no6 direct from the alternator stud to the battery stud on the starter relay.

i did and nothing abnormal... also output line from alt to amp meter is new, i had to bypass the bulkhead when i had my fire...


Go back up and read the MAD article. You have a break in the charging path somewhere.

will do

Also the low voltage you are getting on the "IGN run" lead shows two things:

With engine off, it shows you have voltage drop in the harness, the path from the battery to the ignition feed. This will cause overcharging

With engine running, the low voltage at that point shows it's not charging.

arn't these kinda conflicting as if there is a voltage drop for one there would be for the other, and also you say its low but its within a V of ign side of the reg??
Click to expand...
 
Sounds like an alternator field/brush shorted. Put 17+ volts in for too long, then fried ammeter, and other wires under dash. Mad elecrtric, 2nd diagram, then trace under-dash wiring. Starting at the ammeter that is now by-passed. Alt is now direct to batt, either alt to battery, or just to lug on starter relay. Big power now in engine compartment, just need to feed the small volts into dash.

It ain't fun.
 
green1 said:
Sounds like an alternator field/brush shorted. Put 17+ volts in for too long, then fried ammeter, and other wires under dash. Mad elecrtric, 2nd diagram, then trace under-dash wiring. Starting at the ammeter that is now by-passed. Alt is now direct to batt, either alt to battery, or just to lug on starter relay. Big power now in engine compartment, just need to feed the small volts into dash.

It ain't fun.
Click to expand...


no wires fried... amp meter still had continuity so its ok...

just got back from having the alt tested and it passed... but i was thinking shorted field wire in alt...
 
well i think the easiest thing to do is just remove the dash and install a new/used harness for under dash and engine compartment, then do the "mad" alt mod and also the headlight relay mod...

i was planning on doing the interior anyways, paint dash and what not, so i goes with the flow but i really didin't want to get into it yet...
 
The 28V on the alternator stud indicates that it is "trying" to put out. THAT terminal should be essentially connected directly to the battery -- through the bulkhead -- through the ammeter -- back through the bulkhead -- through the fuse link -- and to the battery

That fact that it is very high voltage and the battery is NOT shows that there is a disconnect somewhere in that path.
 
67Dart273 said:
The 28V on the alternator stud indicates that it is "trying" to put out. THAT terminal should be essentially connected directly to the battery -- through the bulkhead -- through the ammeter -- back through the bulkhead -- through the fuse link -- and to the battery

That fact that it is very high voltage and the battery is NOT shows that there is a disconnect somewhere in that path.
Click to expand...

im understanding that... that why I want to do the Mad Mod...lol but the harness thats in it (underdash) is just so hacked up from previous owner that i figure i should just get a good known harness in it to help prevent future issues...
 
ok so i by-passed the amp gauge... no dice... so im still breaking up somewhere...

looks like a 6ga wire is next lol...
 
The problem HAS to be in this circuit path (look at the simplified diagram in the MAD diagram)

From the alternator stud, (check the ring terminal too!!) through the bulkhead connector, and to the ammeter.

Your accessories feed "back" from the battery -- fuse link -- bulkhead connector -- ammeter -- in harness splice.
 
67Dart273 said:
The problem HAS to be in this circuit path (look at the simplified diagram in the MAD diagram)

From the alternator stud, (check the ring terminal too!!) through the bulkhead connector, and to the ammeter.

Your accessories feed "back" from the battery -- fuse link -- bulkhead connector -- ammeter -- in harness splice.
Click to expand...

again i by passed the bulk head when i had the horn circuit melt a bunch of wires (in 2009) and cut out and soldered in new wire, including the feed line...

i was under there today and the splice was not broken...

and i have been looking at that diagram for the last three days lol...
 
ok so im still trying to track down a 6ga wire but i went ahead and bought a new VR... no change...
 
Find yourself a "heavy load" for a test lamp. That is, an old headlight, or a stop/ tail lamp with the stop and tail filaments wired together.

Hook it to the alternator post. I'll bet there's nothing there.
 
well good news! running a 10ga wire from the alt to the battery did the trick... it immediately dropped from 28 volts to 15 volts... was great to finally take it out for a drive!
 
Pretty much what I expected. You have a "break" somewhere in the harness in the charging lead
 
67Dart273 said:
Pretty much what I expected. You have a "break" somewhere in the harness in the charging lead
Click to expand...

well when she gets her turn for a resto i will get a new harness and then do the mods in that artical...

thanks guys
 
Glad to read you finally got it figured out......just in time for the scorching summer.....
 
inkjunkie said:
Glad to read you finally got it figured out......just in time for the scorching summer.....
Click to expand...

haha its not bad... i like the heat... also means night time racing... which oddly enough i like better, easier to focus....
 
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