Wiring Harness 28-29 versus 30-31
 

The vendors list wiring harnesses for 1928-29 as different from those for 1930-31. I need to replace one in my 1931 standard coupe and have an NORS Twolite harness that has no markings that indicate part number of year of use.

What is the difference between the 1928-29 and 1930-31 harnesses?

Re: Wiring Harness 28-29 versus 30-31
 

One difference is the location of the stop light switch.

Re: Wiring Harness 28-29 versus 30-31
 

So how does one tell the difference?

Re: Wiring Harness 28-29 versus 30-31
 

The original H-type headlights had a single bulb, two wires, bright and dim. Cowl lights were optional with added wires. TwoLite headlights (early 1929) had a parking light bulb in the headlamps with an additional wire in the larger conduit. Deluxe models had only a single headlight bulb with cowl lamps for park.

Today's harnesses are made for either two-bulb headlamps or single-bulb headlamps with a pigtail for connection to a cowl lamp harness. There is no distinction as to model year, however they are made for TwoLite switches, and need to be rewired to the older switch contact bodies.

Re: Wiring Harness 28-29 versus 30-31
 

I am aware of the evolution of the Model A lighting systems from 1928 onward. However, if there is "no distinction as to model year" I am curious as to why the vendors list different part numbers and prices for the 28-29 versus 30-31 harnesses? Something must be different.

Re: Wiring Harness 28-29 versus 30-31
 

The basic difference, as someone mentioned earlier, is the location of the stoplight switch, necessitating different lengths of wiring on the leads that go each switch. The 28/29 stoplight switch mounts on the transmission tower whereas the 30/31 stoplight switch mounts off the back of the center frame crossmember. The leads for the switches come off the main harness at the back of the center crossmember at the lower frame rail on the driver's side of the car. The distance from that frame rail to the 28/29 switch is significantly further than that of the 30/31 switch. So, the stoplight switch leads on the s8/29 harness need to be longer. I know of no other differences in the harnesses but that difference is significant. That said, since the 28/29 harness has longer leads and you are installing the wiring on a 30/31 car ............. and assuming you have a 30/31 stoplight switch mounted on the center crossmember ........... it shouldn't matter which one you have. Either year harness will work on a 30/31. Not so for a 28/29 application.

Re: Wiring Harness 28-29 versus 30-31
 

Thanks again, bobbader!