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MGC Charging system woes - MGC

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rick_ingram

rick_ingram

Yoda
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OK...

Went to fire up the 1968 MGC last week..reconnected the battery ground...tried to fire it up....it was dead. (No surprise....so is/was the Nissan 300zx, the '69 MGC, and the '78 MGB!)

I disconnected the alternator and put the charger on it.

Yes...Negative to negative and positive to positive.

Battery appeared to re-charge on trickle...

Went to reconnect alternator and ...SPARK!

"This ain't right, I say!"

Pulled the one wire off of the alternator that I had connected (brown).

Then...

I disconnected battery at ground (negative terminal).

Reconnected alternator.

Went to reconnect ground....SPARK at battery terminal.

"This ain't right, I say!"

Any clue as to what's going on here?

Thanks in advance
 
No clue whatsoever.
/ubbthreads/images/graemlins/grin.gif

What car you bringing to MER?
 
Trunk or doors open? Interior lights on? Radio on? Any of the hot wires will be able to cause a small spark at the battery when its reconnected. Or might be a short somewhere with a brown or purple wire.
 
When I originally reconnected the alternator, there was nothing open other than the bonnet. When I receonnected the battery the second time around, the passenger door was open..

Janel...aRick and I use his 1974 MGB/GT for the rallies..The Duct Tape Special!
 
I'm more of a "pound of cure" kind of guy.

I say..........RUN IT.

If it blows up..........

Follow the smoke trail back to the faulty component & replace.

You may not want to take my advice.......I understand /ubbthreads/images/graemlins/grin.gif
 
I know the drivers door will close the circuit for the "map light", not sure about the passenger door though. Not sure what might cause the sparks if everything was off and nothing but the bonnet was open. Maybe the alternator needs checking out? Or maybe there's a short somewhere in the system?
 
Check to see if you left the ignition on. I did that and forgot I had it on. Like Doc says anything on fan, etc, will cause the spark you are talking about.
 
OK...The saga continues....

I swapped out the battery just in case it was a short in the battery itself.

I connected the alternator back up (black wire on top, brown beneath it) and reconnected the battery.

It SPARKED at the negative terminal.

For grins, (I would say tickles and grins, but I didn't want to get shocked), I disconnected the alternator and reconnected the ground to the battery. NO SPARK.

I verified that the ignition is indeed switched OFF.

I have a feeling that the alternator, or maybe the alternator control box, is at fault.

In this model of MG, what does the Alternator Control Box do as a function? Could the fault lie here? (My '69 MGC does NOT have this feature.)

Also noticed the one time I did get the C started (a few weeks ago), that the tach would jump to 7000 rmp or so until the car started, then show normal rpm.
 
I guess I'm not sure what an Alternator control box is. An external voltage regulator?
 
that's what it sounds like to me...

also sounds like there might be some bad wiring going into the alt'nater, a short in the voltage regulator, OR a short within the alt'nater itself. Disconnect the alternator and battery and test for continuity between the wires and ground (should be Open). If that checks out ok, I'd have the alternator checked out. Does this alternator have an internal voltage regulator (on the alternator), or an external voltage regulator? I haven't given it much though as to how to check the v-regulator, but it could be done if you have the wiring diagrams for it. I'm sure there are some others around here that'll be able to tell you how to check an external voltage regulator.
 
The only external voltage regulators I know are realllllly old american car regulators.... file the points in them and lube the hinges and they works again like new.

Way different here I'd guess though... How much is a replacement? I'd try that first. Is there a diode pack in there? they are usually the first thing to go.
 
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