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Re: Electrical woes

To: DANMAS@aol.com
Subject: Re: Electrical woes
From: gofastmg@juno.com (Rick Morrison)
Date: Thu, 12 Feb 1998 16:22:56 EST
If any body figures this one out, please please post the answer. My 74
Midget would continue to run when the switch was turned off. I cleaned
connections,  checked wireing, ad nauseum. The only way I was able to
stop it was to replace every  piece of wire in the ignition circuit, from
the solonoid, through the switch to the coil. I never found a shorted
wire, burnt insulation or crossed connection. I live in dread that one
day, when I least expect it, ........ GOTCHA!
Rick Morrison
72 MGBGT
74 Midget
On Wed, 11 Feb 1998 16:06:05 EST DANMAS@aol.com writes:
>Bob Torrens wrote:
>
>"I have a '78 MGB that refuses to stop - sometimes!  The ignition key 
>is
>removed and one of two things happens. Either the car continues to run 
>or
>within 30 seconds after removing the key, the ignition light and 
>cooling fan
>come on."
>
>To which Bob Allen replied:
>
>"Have your alternator checked. Leaking diode."
>
>And Art Pfenninger replied:
>
>"Bob when you say continues to run, do you mean it runs as if the 
>ignition
>is still on? If so you need a diode spliced into one of the alternator
>wires. What is happening is the alternator is sending power back into 
>the
>run on valve and it continues to run."
>
>Bob and Art,
>
>I'm afraid you have me stumped on this one!  For the life of me, I 
>can't
>figure how either of these could be the problem.  When you shut off 
>the engine
>in any MGB, the alternator continues to produce 12 volts for as long 
>as it
>takes for the engine to coast down.  The only thing that keeps this 12 
>volts
>from being fed to the ignition system is the alternator warning light.
>Without the isolating function of the warning light, you would never 
>be able
>to get the engine shut off.  With the warning light, nothing else 
>should be
>required.
>
>Since the alternator is producing 12 volts in the first instant after 
>the key
>is turned off, it would not matter if the alternator diodes were 
>leaking or
>not - 12 volts is 12 volts, regardless of how it came to be there.
>
>The anti-run on valve is on the opposite side of the warning lamp from 
>the
>alternator, so it would not receive voltage from the alternator 
>anyway.
>Besides, the anti-run on valve only shuts off the fuel, not the 
>ignition.
>Even if it were to stay open, the engine would only *diesel* at worse, 
>and
>would not run smoothly, nor run very long.  If it were the anti-run on 
>valve,
>the problem would exist in all of the later MGBs, and would have been 
>there
>from the beginning.
>
>What am I missing?  Is there some tricky circuitry on the later MGBs 
>that I am
>overlooking?
>
>Dan Masters,
>Alcoa, TN
>
>'71 TR6---------3000mile/year driver, fully restored
>'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion 
>- see:
>                    http://www.sky.net/~boballen/mg/Masters/
>'74 MGBGT---3000mile/year driver, original condition, slated for a V8 
>soon!
>'68 MGBGT---organ donor for the '74
>

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