Ammeter Hook up confusion

Carb Guy

Carb Guy

Senior Member
I am starting to work on my car again. I have two questions, on the ammeter does the yellow wire go on the charge side or the discharge side and conversely the yellow with the black tracer, and the dash light wire to which side. Then what is the hook up at the junction box, I see it both ways at different diagrams and other information on wiring, what is right??? Also the red wire from the coil to the pop out switch, I have an original slant pole coil on the fire wall, does it go to the passenger side or the driver side and the black wire from the coil to the junction box also pass. or driver? Thank you very much
 
Try this (the diagram on the left): If the ammeter reads backwards, reverse the wires.
 

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You might want to download a wiring diagram. It was changed sometime during the production run. Around 1929 sometime I think.
Someone may be able to post the diagram for you. I tried and failed. I can't figure out how to do this stuff.
 
Thanks Patrick & Carl. I have several diagrams and pages on wiring and they are conflicting. I just need someone to tell me in simple terms how to hook this up as to drivers side or passenger side and charge side or discharge side and same thing at the coil and the junction box, I wish to have it hooked up right the first time and not have to tear into it again. Thanks to all.
 
The diagram at http://www.webjunk.com/modela/wp-content/uploads/2008/02/wiring-diagramcolor2sm.jpg is probably the best out there.

You'll note that the ammeter is a little "vague" on the diagram - like which side should the yellow and which side should the yellow/black be wired to.

The answer, as others have indicated above, is found in actual service. With no engine/generator running, putting on a light should result in the meter going to "minus" on the dial. This will assure you that you see "positive" when the engine is running - and you haven't out-run your generator capability.

Hope this helps.

Joe K
 
Thanks Joe

I have this diagram printed out in all my wiring information and it is one of the best. looks to me like the yellow wire goes to the discharge or the drivers side of the ammeter and then on to the pass. side of the junction box and then to the starter switch. the yellow with black tracer goes to the charge side or the pass. side of the ammeter and then to the driver side side of the junction box and then on the the cutout. the instrument light to the pass. side of the ammeter The red wire goes from the passenger side of the coil to the pop out switch and the black wire from the coil to the driver side of the junction box. Is this the way all of you look at this, if so then this how I am going to wire it. Thanks again to all of you
 
Just to illustrate how the wiring options differ. Look at Brattons catalog on page 70 at the bottom of the page it says just the opposite of what the wiring diagram shows. Who is right that is my question?
 
Wire it just as you posted in #7 then turn the lights on. If the ammeter shows charge, then reverse the wires on the back of the ammeter. Connect the instrument light wire to the ammeter post with the yellow/black wire, so it shows discharge if left on. Install the black coil wire to the terminal box post with the yellow/black wire so it also shows discharge if the key is left on and the points are closed.

Originally the coil black wire went to the terminal box post with the yellow wire that runs down to the starter switch. This way the coil draw doesn't show on the ammeter, which I didn't like, so I changed my 28 to the other side. Changing to the yellow/black terminal box post also makes it easy to see if the points are conducting when the key is on and the points are closed.

As a final check for coil polarity, check what Chicagoland MG Club has written about it.

http://www.chicagolandmgclub.com/techtips/general/574.html
 
Tom Wesenberg said:
Wire it just as you posted in #7 then turn the lights on. If the ammeter shows charge, then reverse the wires on the back of the ammeter. Connect the instrument light wire to the ammeter post with the yellow/black wire, so it shows discharge if left on. Install the black coil wire to the terminal box post with the yellow/black wire so it also shows discharge if the key is left on and the points are closed.

Originally the coil black wire went to the terminal box post with the yellow wire that runs down to the starter switch. This way the coil draw doesn't show on the ammeter, which I didn't like, so I changed my 28 to the other side. Changing to the yellow/black terminal box post also makes it easy to see if the points are conducting when the key is on and the points are closed.

As a final check for coil polarity, check what Chicagoland MG Club has written about it.

http://www.chicagolandmgclub.com/techtips/general/574.html
Click to expand...


As verification for the above, I just replaced my junction box and replaced dash wiring. It was done as above and I had to reverse my wires at the ammeter from the per spec diagram. This was done as Tom above and others have pointed out. There have been several posts on other threads about ammeters being reversed.

This was a good thread for clarification.
1) There are two ways to wire a standard Model A, factory:
a) Pre-29 b) Post-29
2) With engine off, lights on, the ammeter reads a discharge. If not, simply reverse the wires on the ammeter. Done.
 
Thank you Tom and all of you who have posted on this thread, it has been great to hear from all of you and has been a great help to me and I hope to others also. Thanks again
 
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