Long story short, I needed to install a tach to see where my rpms sit. knocked my electric fan switch loose and crossed the wires. electric fan won't work now, and my charging system is showing discharge. I've been through testing and I can't figure out whats wrong.

Blue wire at the voltage regulator is showing 10.56 volts, green field wire is showing 1.06 volts... I've changed out the wiring, the voltage regulator, and now I gave up and replaced the alternator... None of which have helped. All the readings stayed the same. I've run out of ideas on what to check, and I know it's probably something simple.

Oh yeah, GD tach won't work either.

blue wire is system voltage at the VR. at 10v the vr should energize the alt field to give a high output. with the green wire at 1v, that would give you about 9v cross the field on the alt and make it charge.

did you recently paint the engine? if the alt isnt grounded, it wont charge.

Measure the voltage across the battery terminals and post it.

measure the voltage across the two filed wires AT THE ALT and post it.

then measure the voltage at the Alt between the black output and the ALT case and post it.

then measure the voltage between the black output at the Alt and the Batt ground and post it.

make sure the voltage regulator CASE is grounded to the chassis. Use an ohmmeter to verify the case is grounded. also check to see the alternator is grounded. go between the case and battery ground

At a fast idle jump the "green wire" male alt field terminal to the alt case for 3 seconds max (not the green wire but the brass terminal).If it charges work on that circuit (from the green wire female connector over to the VR). If no go then keep the above grounded and jump fire from either the large alt batt stud (easier) or the battery positive post (try both) to the other alt male field terminal (the blue wire one) for 3 seconds & see if it charges. Still no go?, pull the brushes real quick & eyeball them. Holler back.

check the fusable link!

Fusible link goes out you will have no power to anything inside so that won't be it.

did you recently paint the engine? if the alt isnt grounded, it wont charge. No I have not

Measure the voltage across the battery terminals and post it. Engine off: 12.75 Engine on dropped it to 11.8

measure the voltage across the two filed wires AT THE ALT and post it. 9.2

then measure the voltage at the Alt between the black output and the ALT case and post it. 41.6

then measure the voltage between the black output at the Alt and the Batt ground and post it. 41.6

make sure the voltage regulator CASE is grounded to the chassis. Use an ohmmeter to verify the case is grounded. also check to see the alternator is grounded. go between the case and battery ground Took off the Regulator and sanded the firewall ground spot to make sure its got good contact

true- since a short on the system can cause all sorts of issues- maybe the diodes in the alt are toast!

If the alternator is charging wildly high look for a shorted field terminal. Pull the unit off and make sure the porcelin insulators the brushes sit in are intact. I've seen the insulator break and short the field spade clip to the screw that hold it in place. Dave

Check the wiring that goes up to the oem amp gauge from the ign switch and junction block.Those factory amp gauges can be a pia in mhop

The alt is charging but the output is not making it back thru to the rest of the system. Check the voltage at the alt lead at the firewall and at both sides of the ammeter. A bad bulkhead connector or bad ammeter connections or bad ammeter.

I'd have to review the schematic to figure out where else to look.

In my attempt to figure this out I have replaced the voltage regulator, alternator, and the green field wire with new parts... What sickens me is that none of the old parts were bad. I'll have to get under my dash and check the readings at the ammeter

look, if you are getting 41v at the back of the alternator BUT only 120v or so at the blue wire, that means the alternator voltage is not making it from the alternator back to the rest of the system.

look at a schematic. the alternator output goes through the bulkhead connector and then to a slice under the dash that feeds the rest of the car including the blue wire at the VR after it goes through the ignition switch. for some reason, you have voltage at the back oif the alternator that you dont have at the VR or battery so the alt voltage isnt making back.

get a schematic and find out where the connection is broken using a voltmeter or ohmmeter