Subject: Re: [Tigers] MK II wiring help

From: " Ron Fraser" <[email-masked]>
Date: Fri, 27 Apr 2012 12:38:21 -0400

Theo
	I have not checked the system thoroughly but your last statement
seems to ring true.  I don't think I ever saw the amp gage go anywhere but
to the negative side.  I need to do some better testing and observation of
this system the next time I work on it.

	Any idea how an amp gage should be wired into this alternator
system?
Thanks
Ron

-----Original Message-----
From: Smit, Theo [mailto:[email-masked]]
Sent: Friday, April 27, 2012 12:21 PM
To: [email-masked]; [email-masked]; [email-masked]
Subject: RE: [Tigers] MK II wiring help

One way to evaluate the overall wiring correctness (regardless of where,
physically, the connections are made) is to observe the ammeter readings
under some different conditions: 1. Everything off: Reading is at zero. 2.
Ignition off, headlights on: Reading shows about -8 amps (discharge due to
about 100 watts of lighting) 3. Headlights off, ignition on, engine not
running: A small negative (discharge) value. Turning on ancillaries such as
heater, wipers, brake lights, headlights should each show negative values
according to their approximate current draw. 4. Engine running: You should
get a positive reading, starting at a higher value (20-30 amps) immediately
after the engine is started, tapering down to probably about 5-10 amps after
a few minutes. This should not change if you turn on headlights, or other
accessories, although the needle might flicker when you first turn on or off
heavy loads such as the headlights.

If you only ever get readings in one direction then it's miswired.

Theo
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From: Tod Brown <[email-masked]>
Date: Fri, 27 Apr 2012 15:37:55 -0400

Ron:

I don't know if this will help but the Shop Manual shows the wiring for 
an ammeter for a MkIA but not for the MkII.  I know the ammeter was 
optional on the MkIA and the wiring diagram shows the ammeter with 
dashed lines replacing the wire that runs from the "B" (Battery) 
terminal on the voltage regulator to the terminal on the solenoid that 
is connected to the positive battery terminal.  I conclude from this and 
seem to remember that, on my MkIA, the large brown wire going to the 
voltage regulator comes from the solenoid rather than directly from the 
alternator/generator.

At least some of the MkII's had ammeters that matched the other 
instrumentation but it does not look like they were delivered from the 
factory that way which is probably why it is not shown on the wiring 
diagram.  Since the MkII's used alternators, I recollect that the 
ammeter range was higher,  + or - 50 amps, while the MkIA's were + or - 
30 amps.

In the CAT Notes there is an entry entitled, "Ammeter Installation" from 
Greg Tuttle added in the Mid-70s, it says.  To quote,

"... Before doing anything, disconnect the battery. ...

Next, remove the large brown wire from the top pole of the voltage 
regulator.  Remove connector and solder splice another piece of 10 ga 
wire and run back through the firewall to the + (plus) side of the 
meter.  Run another piece of 10 ga wire from the - (negative) side back 
to the regulator and attach to top pole.  Use suitable connectors at all 
four points, as a lot of current passes through them.  Tape splice as 
necessary.

Wire lamp by inserting plug on red wire into connector in harness under 
dash; ground black wire to tach mounting post.

Check that connections are tight and well insulated and reconnect 
battery.  Turn lights on and verify needle moves to - or discharge side 
of meter.  If needle shows + or charge with lights on, reverse the two 
wires on the back of the meter."

Although the instructions may have been written for the MkIA, they 
should also work for the MkII because the large brown wire, in both 
cases, carries the current to and from the positive terminal of the 
battery, and that is, of course, what you want the ammeter to read.

Good luck,

Tod
B382002384LRXFE

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