Nu Rex ignition switch

[rotorwrench]

The new type switch can be connected to either control power from the battery to the coil or the ground pathway between the coil and the breaker points in the distributor. We would need to know which way the new switch is connected to give the best advice.

Ford used the Electrolock switch/cable assembly to control the ground pathway from the coil to the breaker points in the distributor. Modern systems control the power to the coil from the battery.

The distributor also has the little wire that connects the lower plate to the upper points plate. It has to flex when the spark advance control is changed so it can be a problematic at times. A bad condenser can kill the ignition function so always keep a new A&L spare around for testing.

[rich40701]

I just installed the Nu Rex ignition switch but luckily my A had been converted to electronic ignition before I got it, and a similar switch was used with two wires. I like the original look of the Nu Rex ignition switch. The site touts the switch to be made in USA but after receiving the switch says made in Mexico assembled in USA or vice versa. Made in USA should mean "MADE IN USA", period.

[Rob Doe]

Guyz, Katy's diagram in post 13 shows the power side of the coil as the - neg and the distributor / points side as + pos. It also implies a 12v system. Unless he has a 12v positive ground system, his coil polarity would be reversed???? Am I cornfused????

[Y-Blockhead]

Originally Posted by Rob Doe

Guyz, Katy's diagram in post 13 shows the power side of the coil as the - neg and the distributor / points side as + pos. It also implies a 12v system. Unless he has a 12v positive ground system, his coil polarity would be reversed???? Am I cornfused????

Rob, sorry for the confusion. I posted that picture in post #13 and it is incorrect. I have deleted it. Thanks for keeping me honest.

[Rob Doe]

Tiger2, post 19:

The diagram in post 13 is nicely drawn. It is easily understood by experienced Model A persons. It is lacking a few details that will be needed by the beginner Model A person that is wiring his car for the first time.

The diagram shows a 6 volt battery with the + pos post grounded to the frame. It is important that the newbie know what battery and which cable is grounded to the frame. 12V or 6V, and Pos + or Neg - grounding is being used. A 12V, negative ground system requires a reversal of the wires at the ammeter and the coil from those of a 6V + positive ground one.

Professional wiring diagrams (for those with formal training) are generally drawn with no relationship of the components to their actual position in the vehicle. Components are identified within a symbol. Actual component positions in the car might be commented on the diagram in a convenient location. IMHO, this drawing is a duke's mixture as it depicts renditions of the components and their somewhat relative positions in the vehicle, which actually helps the beginner. However, it lacks the markings of + plus and - minus on the key components. The perspective of the drawing seems to be from the front of the car looking toward the firewall.

Assuming it is the backside of the ammeter that is depicted, the two wires attached there should be drawn with one crossing over the other. The ammeter will read backwards if these connections are incorrect side to side. The wires that run from the terminal box studs to the ammeter on a stock Model A are not yellow and yellow. They are yellow and yellow / black stripped. Refer to the front face of the ammeter for proper connections.

At the ignition coil on a stock Model A, the short black wire that is sourced from the terminal box powers the primary coil winding. It must attach at the - neg post of the coil and the opposite post, the + pos post must power the ignition points via the switch, else the polarity of the spark at the spark plug will be reversed causing a weak spark. The car will run, but it may start and run poorly if there are poor connections or weak components. There are methods to test the polarity of the ignition.

There is a service bulletin which moves the source of the short black wire, which powers the coil primary from the yellow wire / terminal box stud to the yellow / black stripe terminal box stud. This bulletin can be found in the November 1929 chapter. This change causes the opening and closing of the ignition points to be depicted on the ammeter when starting the vehicle and at lower rpms. This is useful when diagnosing ignition problems. The newbie should make sure he is wired accordingly.

Snyder's Model A Parts sells a very good 11 x 17 wiring diagram, which is produced on a rugged plastic sheet for a small amount of money. It depicts the last of the wiring changes for the Model A 28-31.

https://www.snydersantiqueauto.com/p...6763&cat=41801

I hope someone finds this post helpful.

[Tiger2]

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Rob Doe Post #25. Thank you for your information! It indeed was helpful. Jim Cannon suggested that I may have tightened the Nu Rex armored cable into the distributor too far, When I backed the cable out a bit I felt and heard a "click" and just knew that things were improving. My 1931 coupe started right up with no blown fuse and no smoke. Thanks again fellas for taking time to give me direction on this.