This is not my truck so thanks to Marky48170, I'm using his cause its a great picture and looks just like mine.

See the wire running from the bottom of the picture (the black and yellow one) to the power distributing block that comes from the Alternator 1G, it connects to the batt connector on the alternator, also on the back of the alternator is the ground which is connected just below the bottom support bolt to the block. a white wire to field and a white and black wire runs to stator, towards the bottom of the alternator is an open terminal with a white insulator and no markings(not in use). Every thing in the picture is exactly like mine, when I connected the neg batt cable it sparked so bad it melted the lead from the terminal, I disconnected the wire running from the alternator to the power block, reconnected the battery and no spark, power reaching the top 2 wires in the picture on the power block and no power to the truck. When I grounded the wire comming form the alternator (the black and yellow one) all power worked to the 1966 F-250. Would having the stator and field wires wrong cause this to happen? Its not possible I have the Batt and ground mixed up because of the size of the lugs on the back of the alternator, the Batt is larger than the ground.
I have looked at countless wiring diagrams been searching the internet for 3 days now, they dont make sense and none of them match my set up. People talk wire color, schematics show color but the colors don't match, I have stock wiring 1966 Ford F-250 2wd 352 NP435 4:10, this picture matches exactly.
Two grounds coming form the alternator ya don't think that's right.
Any help will be much appreciated

 

When you grounded the combined black and yellow wire, you said everthing worked??????????????? Did the engine start, run and the alternator put out power?

I am guessing not....

Anyway.....
Verify you have the neg battery post to the negative cable to ground and the positive to the red. This should always be verified before troubleshooting.

Then disconnect all the wires at the terminal block, clean the connections, quickly touch them together to see if there is a spark indicating a ground.

If not..... bolt them together and wrap them with insulating tape then friction tape and replace the terminal block because it is grounding out.

Find the other terminal block and do the same if someone has not already done so. These blocks are crappy nasty items that short out.

If there is a spark, disconnect the other end of the yellow wire and retest to isolate the problem to one wire or the other. If the B wire is grounded, then alternator diodes are burned out or the B connection is grounding out or there is a ground in the wiring.

If the yellow is grounded chase that problem.

Good luck.

 

Thank you, just finished a monster rebuild on engine (shes a 390 now with sick flowing heads and a mean cam, block and oil pan are about the only thing original) and tranny, need to find where I went wrong with the wiring before I fire the few thousand dollar engine. Engine bay and all connections are clean, I guess tomorrow I will be playing with sparks and praying to Father Tesla instead of engine timing, dang dang dang. FTE Best forum in the world.

 

distribution power block doesn't show to be grounded, positive terminal on alternator shows grounded. Does this indicate bad alternator? I'm thinking YES

 

FIXED, Alternator was fried

Hooked up the new one and no sparking