Help with MSD 6AL and billet distributor set up

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str12-340

str12-340

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I'm looking for some help with my MSD 6AL system. This is the old non-digital set up that I've been using for 20 years. In running diagnosis there are 3 wires TO the box: a red and a black big wire that goes to the Battery and a serious ground, and a small red wire that connects to the original positive lead to the coil that comes out of the wire harness back near the coil. The big wires show exactly the same voltage as the battery at all times. My small red wire, which turns on with the key in the "run" position shows 6 volts, both at the original wire from the harness (grey) and at the box. Is this right???? Is there something in the system that reduces this voltage for some reason?

Wires that run OUT of the box are an orange and a black wire that goes to the coil, and a pair of wires that go to the distributor (which is a newly rebuilt pro billet - work done by MSD). Is there any way for me to check that these wires are doing what they should?
 
Are you sure your coming of the right sides of the ballast resistor?
 
first...you dont use the ballast resistor with the msd 6a.....the red wire that turns on the msd unit needs 12 volts during start and run....if it was converted from a mp box....you usually hookup the two wires on the ballast resistor which is run and start....if you are getting only 6 volts there.....you are going to have to trace those wires to see what is happening...or you can bypass that wire and run new wires to the msd unit...
 
I agree with above. I eliminated the ballast resistor with my 6A. That's gotta be what's happening seeing the voltage is exactly halved.
I usually just wire that big black back to the battery neg. also.
Good luck
 
I'm following up on the advice, looking at the wire routing on the original harness to figure where wires come from and then testing at either end. I think you guys are on to something about the wrong wire hooked up from the ballast resistor. What blows my mind is that I installed this system in 2005 and it had worked great until it didn't a few weeks ago. I sent the original 6AL box to MSD to see if it was screwed, and to get it rebuilt for a back up. I'll let you know what turns up.

More suggestions of stuff to test are welcome!
 
You (likely) don't have the wrong wire and this has been discussed many times. There is only one "run" voltage source in the enigne bay, and then there's the coil bypass circuit. "Run" is IGN1, and "bypass" is IGN2. You need to bypass the resistor and connect the old coil + lead to the small red

IGN1 feeds one end of the ballast, IGN2 goes to the coil end. By bypassing the ballast, both those are now connected together, and feed the small MSD red. The IGN1 is hot ONLY in run, and goes "cold" in start. The IGN2 bypass circuit is hot only in start, and was originally to feed "hot" battery to the coil during cranking

Also do NOT connect anything to the coil except the two wires from the MSD box. Not the tach, and not the old radio suppression cap
 
67Dart273 said:
You (likely) don't have the wrong wire and this has been discussed many times. There is only one "run" voltage source in the enigne bay, and then there's the coil bypass circuit. "Run" is IGN1, and "bypass" is IGN2. You need to bypass the resistor and connect the old coil + lead to the small red

IGN1 feeds one end of the ballast, IGN2 goes to the coil end. By bypassing the ballast, both those are now connected together, and feed the small MSD red. The IGN1 is hot ONLY in run, and goes "cold" in start. The IGN2 bypass circuit is hot only in start, and was originally to feed "hot" battery to the coil during cranking

Also do NOT connect anything to the coil except the two wires from the MSD box. Not the tach, and not the old radio suppression cap
Click to expand...

Thank you for an excellent clear description! I presume that the bypass is just a connection between the wires at the ballast resistor? At that point there's no reason to even retain the ballast resistor at all? Just make a neat connection between the two wires on one side and the single wire on the other side, right?
 
str12-340 said:
Thank you for an excellent clear description! I presume that the bypass is just a connection between the wires at the ballast resistor? At that point there's no reason to even retain the ballast resistor at all? Just make a neat connection between the two wires on one side and the single wire on the other side, right?
Click to expand...
Yes.
Also make sure the firewall connectors for IGN 1&2 are in good shape if you have supply voltage issues.
 
OK time to confess... somewhere in this process I switched two wires that come out of my harness in the same place. One was the original wire to the coil+ and the other went to the Temp sending unit (long abandoned for a mechanical gauge). That's why the wire showed 6 volts. But this thread is leading me to deal with other wiring issues like eliminating the ballast resistor. I'm good at the bulkhead connector - replaced the dash wiring harness in December and cleaned up and greased all the connections when I did it.
 
What I was referring to was it coming off of the straight voltage side. The resistor is taken out of the equation some just use the terminal where power lead connects to jump off of it. It's pretty clear if you look at the diagram.
 
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