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Discussion Starter · #1 ·
I need to install a wire from an ignition switched source to my alternator. (to the internal regulator actually) I can use either the old external voltage regulator wire or the electric choke wire. The problem is, I've been told I will need to use a diode in the wire to prevent "drainback" to the ignition switch. This "drainback" would cause my MSD 6A to remain powered up even with the ignition switch off. Which means I couldn't shut the motor off.

All I know about diodes are that they are like one way valves that allow current to run in one direction only. Aren't they? What I don't know is what kind or size I need and how do I wire it in? I am completely clueless when it comes to diodes and resistors, etc. Any help would be much appreciated.
 

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That's how I would describe a diode in laymans terms. As far as what size you need, I have no clue. I think they are rated for current and /or voltage. If you know how much current will be drawn throught the wire, you could probably go to radio shack or similar store, and they could probably help you get what you need.

Why are you having to do this? I'm just curious.
 

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I'm assuming this is to prevent leakage from the internal regulator back into the electrical system? I've never heard of having to do that.. The alt should have that built in. But anyways, if there isn't a diode in the alt, there shouldn't be more than an amp or two allowed to leak back. You need to find a 6A04, 8A04, or 10A04 diode. These are rated 6,8,and 10A respectively @400V, so there'd be no danger of burning them out. I think you'd have to go to a regular electronics store to get diodes that big though.. I think ratshack only has the 1N4XXX series, which are only 1A. When istalling it, you simply need to put it in the line with the striped end toward the alternator. Power flows through a diode from the side without the stripe to the side with the stripe. It will not flow the other way. I would tie it to the old regulator lead, since that will give a good picture of the voltage at the main splice.

Matt {peace}
 
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Discussion Starter · #4 ·
I went to RadioShack and asked the guy for the numbers you gave me, Matt. He just stared at me and pointed at the wall. I think he had less of a clue than me. With your help I was able to pick out what I needed. Once again your advise has helped me immensely. Thanks. {cool}

I've installed a 3 wire Delco Remy alternator on my truck. Apparently the Delco does have a slight current flow thru this wire when the ignition is off. It's enough current to keep the MSD box fired up. What I have is basically a GM style charging system in my Dodge.
 
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Discussion Starter · #6 ·
Hell I don't know, I own a Dodge. ;D

They do if you install an MSD.

Which reminds me, [email protected]#@$#@!!$%%^, I kept the diode from the MSD kit. I didn't have to go to RadioShack. Does senility count as a Workers Comp injury?
 
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Discussion Starter · #8 ·
You mean the "craparo" that can kick your scrawny butt and leave you groveling in the dirt like the backwoods Mopar owner that you are? ;D

Yeah, I still have that. I just forgot about it for a minute. Told you I was senile.
 

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Watcha Camaro do in the 1/4? I gotta 85 'Bird that does it unofficially in 13.5 or something like that (had my drag racing buddy time me at our "ghetto strip"). Wanna race someday?
 
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Discussion Starter · #10 ·
This is from the MSD site. It explains it better than I can.

"Engine Run-On

If your engine continues to run even when the ignition is turned Off you are experiencing engine Run-On. This usually only occurs on older vehicles with an external voltage regulator. Because the MSD receives power directly from the battery, it does not require much current to keep the unit energized. If you are experiencing run-on, it is due to a small amount of voltage going through the charging lamp indicator and feeding the small Red wire even if the key is turned off.

Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the parts bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the voltage is kept from entering the MSD."


 

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Gotcha! {cool}
 
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