I've been on this site for a while, but never needed to post a question before because everything I wanted to know has already been answered. It's a great resource.
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I post up on stuff all the time, especially if the OP (Original Poster) has his 'Fix' and the thread is 'Dead', then we use it to socialize without 'Technically' breaking the rules about keeping it strictly 'Tech' when we start threads.
There are a great bunch of guys here, and they have some REALLY good ideas, and their 'Day Jobs' are so diverse it's a great pool of information to draw from!
I've been in the process of rebuilding my CJ5 over the past 3 months and have run into a snag with my alternator excite wire.
I have a (Add Year '76) CJ5, 304, delco alt and have completely gutted the ignition system and installed the teamrush upgrade with an MSD 6al.
The PO completely messed up the wiring, so I'm starting with the engine bay and replacing wire for wire to make it right. He also had the alt excite wire hooked to the "I" terminal on the starter soleniod which through this forum I found out is not correct.
I plan on wiring the system according to several diagrams that I found from Jeephammer.
Connecting to the 'I' terminal ('Hot' when cranking with 12 volts, receives a back feed of reduced voltage from coil resistor wire when key is in 'Run' position,
It's OK to connect there, it will work, just like connecting to the coil 'Positive Terminal'.
Since I want to keep all the engine wiring in the bay, should I splice the excite wire with diode to the wire coming from the 6al going to the coil + OR splice it to the small red wire going to the MSD which is the switched 12 volt circuit?
The 'Small Red' wire to the MSD that is 'Switched' is the way to go.
That switched source is what activates the MSD module (Turns it 'On' when you need ignition) it's PERFECT for the connection for the 'Excite' wire.
DO NOT forget the diode!
Since the alternator draws some power to get started charging,
But then turns into a 'Positive' output when the alternator starts charging,
The diode will be required to keep the alternator from activating/maintaining the MSD module when the key is in the 'OFF' position.
Back feed from the alternator WILL keep the MSD turned 'On' once it starts charging!
Just not sure if this wire needs to go before the MSD unit or afterward. Also, if the existing excite wire is still in good shape, can I still use it and just splice in the diode?
Just run a wire any which way you want to, as long as it's 'Switched Source',
You can splice in, 'T' off the connector for the MSD,
You can 'T' into the line anywhere out to the MSD,
You can even connect at the ignition switch, run through an 'Idiot' light then out to the alternator so you have a 'Warning Light' or 'Idiot Light' for your charging system,
But you MUST use the diode in the line that feeds the alternator,
'Stripe' facing the alternator.
If you go the 'Idiot Light' route, make sure your light socket DOES NOT ground through the socket, it MUST have two wires, one for 'Feed' and one for 'Ground'.
Since you are going in with one 'Power' wire,
Then out to the alternator instead of 'Ground',
You don't want the socket to self ground or the system will short out.
You are on EXACTLY the right track,
And any splice source from 'Switched Run' power will work for you.
You know about the diode if the MSD is on the same feed line, so you have 99% of the concept down, the last 1% is just wiring and seeing if it works...
You have done your homework, you know the system, trust in yourself and do a hookup.
You can't really hurt anything, so experiment a little, then bundle things up when it works for you!