Electrical Gurus- What Caused This?
Thread Starter
Le Mans Master
Joined: Oct 2000
Posts: 6,563
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Electrical Gurus- What Caused This?
I left the key on by accident, and here's the result-
The car has a Mallory Unilite tach-drive Distributor. The harness is (was!) new, and the car never has had a ballast resistor, because it was a transistor ignition car. It also has a GM mini-starter. Any help is greatly appreciated! Thanks in advance-
:yesnod:
[Modified by MassVette, 8:30 AM 2/29/2004]
The car has a Mallory Unilite tach-drive Distributor. The harness is (was!) new, and the car never has had a ballast resistor, because it was a transistor ignition car. It also has a GM mini-starter. Any help is greatly appreciated! Thanks in advance-
:yesnod:
[Modified by MassVette, 8:30 AM 2/29/2004]
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Electrical Gurus- What Caused This? (MassVette)
Either one of two things happened, but the end result for the coil/wiring was the same......as the sender/points side of the coil was grounded pretty hard, tossing the full 12 volts across the coil in a steady state, it just fried as a result....
so either one of two things.....failure of the unilite sender unit/faulty wiring leading to it, OR.....the thing is of poor design, it should never allow the coil to see the full 12 volts across it, unless the engine is running....
I suspect the former, for some reason, as no engineer is that stupid.....
GENE
so either one of two things.....failure of the unilite sender unit/faulty wiring leading to it, OR.....the thing is of poor design, it should never allow the coil to see the full 12 volts across it, unless the engine is running....
I suspect the former, for some reason, as no engineer is that stupid.....
GENE
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Re: Electrical Gurus- What Caused This? (MassVette)
Thanks for posting as I'm having problems wiring my new GM mini.
Okay so we can see that a full 12V is applied to coil with the ignition on. And you have 3 wires to the positive side of coil. One wire should be from the ignition switch - red or orange. Secound wire should be from the starter solenoid "P" terminal - yellow on a '74. Third wire could be from an ignition box (but you don't list one) or electronic tach maybe (but you state mechanical tach) as '79 didn't have any computer box/controls that I recall. Or maybe that third wire I see is just a melting insulation off of red lead?
Now my GM mini only has two terminals on solenoid. So I need to connect my purple lead ('74) from the ignition switch to this slip on terminal (original starter solenoid "S" terminal). And next connect my big red battery (+) cable to the only threaded terminal on the mini's solenoid. Also connect the smaller red wire from the terminal block on fender to the same threaded terminal with a large size lug/ring. Since my GM mini doesn't have a "P" terminal this leaves a fourth yellow wire that connects to the coil positive to either connect to large threaded connector or maybe to the purple wire/slip-on terminal or even maybe just insulate and abandon?
When I connected the purple wire from starter switch to slip-on connector (by itself) and then connected battery cable and smaller red wire from fender block and yellow lead from coil all together onto the threaded term I got continuity everywhere. I got continuity (short - no resistance) from purple wire to case ground. Continuity from purple wire to battery cable and smaller red wire on fender block and to yellow wire. So then I disconnected the yellow wire and still have continuity everywhere.
There has to be an open (high resistance) between purple wire and battery cable when starter switch is off. So I'm getting ready to disasemble the mini solenoid to trouble shoot here.
So to answer your question, there should only be a full 12V at the coil positive when the starter is engaged.
I'm thinking your starter wiring is okay but since you never had a resistor wire or ballast that with the key on there's no transistor ignition to control voltage anymore? Maybe a simple resistance check from ignition switch wire terminal (connector on steering column good enough) to the coil positive (or end of that red wire) should only be a few ohms resistance. If high resistance then problem somewhere else.
There are aftermarket coils that will handle a full 12V continously as you need a replacement anyways - but you need to do the research here.
If you have the opportunity please post how your GM mini is wired. :D As I'm having problems myself and would appreciate your info. ;)
[Modified by cardo0, 2:07 PM 2/29/2004]
Okay so we can see that a full 12V is applied to coil with the ignition on. And you have 3 wires to the positive side of coil. One wire should be from the ignition switch - red or orange. Secound wire should be from the starter solenoid "P" terminal - yellow on a '74. Third wire could be from an ignition box (but you don't list one) or electronic tach maybe (but you state mechanical tach) as '79 didn't have any computer box/controls that I recall. Or maybe that third wire I see is just a melting insulation off of red lead?
Now my GM mini only has two terminals on solenoid. So I need to connect my purple lead ('74) from the ignition switch to this slip on terminal (original starter solenoid "S" terminal). And next connect my big red battery (+) cable to the only threaded terminal on the mini's solenoid. Also connect the smaller red wire from the terminal block on fender to the same threaded terminal with a large size lug/ring. Since my GM mini doesn't have a "P" terminal this leaves a fourth yellow wire that connects to the coil positive to either connect to large threaded connector or maybe to the purple wire/slip-on terminal or even maybe just insulate and abandon?
When I connected the purple wire from starter switch to slip-on connector (by itself) and then connected battery cable and smaller red wire from fender block and yellow lead from coil all together onto the threaded term I got continuity everywhere. I got continuity (short - no resistance) from purple wire to case ground. Continuity from purple wire to battery cable and smaller red wire on fender block and to yellow wire. So then I disconnected the yellow wire and still have continuity everywhere.
There has to be an open (high resistance) between purple wire and battery cable when starter switch is off. So I'm getting ready to disasemble the mini solenoid to trouble shoot here.
So to answer your question, there should only be a full 12V at the coil positive when the starter is engaged.
I'm thinking your starter wiring is okay but since you never had a resistor wire or ballast that with the key on there's no transistor ignition to control voltage anymore? Maybe a simple resistance check from ignition switch wire terminal (connector on steering column good enough) to the coil positive (or end of that red wire) should only be a few ohms resistance. If high resistance then problem somewhere else.
There are aftermarket coils that will handle a full 12V continously as you need a replacement anyways - but you need to do the research here.
If you have the opportunity please post how your GM mini is wired. :D As I'm having problems myself and would appreciate your info. ;)
[Modified by cardo0, 2:07 PM 2/29/2004]
Thread Starter
Le Mans Master
Joined: Oct 2000
Posts: 6,563
Likes: 2
Re: Electrical Gurus- What Caused This? (cardo0)
I dunno the answer about the mini starter wiring- but I saw a post several months ago on here about the same things. There were a couple of detailed responses, if my memory serves me right. To bad I don't remember what the F they were! I was hoping the same guys would help out here-
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