Topic: Replacing cowl wiring on my 40 Mercury


rradar    -- 10-07-2011 @ 5:26 PM
  It all started with a short and burnt wires! So far I have pulled out the defective wiring loom under the dash and I am now in the process of replacing it with a reproduction loom from Dennis Carpenter.

Have learned that the company produced an early and a late wiring loom for this model. I have the late with 2 instrument light bulbs. Also, the high beam indicator jewel light is mounted in the speedometer face not separate on the dash board. The loom I got from Dennis Carpenter was an early one with only 1 dash light. I suppose I will have splice a Second bulb off the first one.

OK, aside from being a real bear to work under the dash things are progressing fairly well. But, there is an issue I'm still pondering.

This car has after market turn signals and it looks like someone spliced a light switch lead with a wire leading down to the ignition terminal. So it appears that there is power going up to the light switch wire and probably is fed down through the parking light wire to the circuit breaker. There is a black wire from the turn signal blinker that must go the circuit breaker left terminal. (Not sure because it wasn't noticed when I pulled the old loom out.)

So, my question is the routing described above the pathway to get power to an aftermarket turn signal system or is this just some Mickey Mouse quick fix??

Appreciate any help, Radar




TomO    -- 10-08-2011 @ 6:51 AM
  The turn signal switch has only one source of power. It is usually wired from the Gauge terminal on the ignition switch. An alternate wiring option is at the resister block on the ignition switch side.

If you have not started to install the harness, I would return it and order the correct one. The early harness has some different tie off point from the later harness, adding to the difficulty of installation.

If you remove the front seat from the car, you can use a pillow to rest your head on while working under the dash.

I hope that I have answered your question.
Tom

This message was edited by TomO on 10-8-11 @ 6:53 AM


rradar    -- 10-08-2011 @ 9:07 AM
  Thanks for the info!!

When you say that the loom has different tie off points, does that mean that some wires will not be in the right position to connect to the terminals that need power?

Unfortunately, I have already started installation and so can't return the loom so I will to make compromises on it. Anyway, the early loom was all Dennis Carpenter had.

One more question on the turn signal wire. It was spliced into the parking light wire on the light switch. The splice was soldered in but the entire wire was bare. I wrapped the wire with electricians tape but now I think the entire wire should be replaced up to the splice. Also, I started wondering if all the other burnt wires near this turn signal wire (at the ignition block) were a result of overheating of the turn signal system.

Needing a little information as I don't want power up the wiring before I get it right!

Thanks for helping,
radar


supereal    -- 10-08-2011 @ 10:46 AM
  The turn signal syatem is powered by a connection from the ignition switch to the flasher. It should be fused with at least a 15 amp fuse. Many aftermarket turn signals are installed poorly. If you need a generic diagram, I can post one for you. We just used it last week to fix a system that kept blowing fuses due to a shorted indicator light.


rradar    -- 10-08-2011 @ 4:05 PM
  Thanks guys for your help!!

Still pondering what the purpose would be of a spliced in wire from the ignition switch to the parking light switch wire. Looking at the schematic supplied by Dennis Carpenter, it appears that the 16 ga. Black wire w/yellow tracer goes from the dash light switch to the circuit breaker. So, no pathway to the turn signal flasher. Therefore, I could eliminate the spliced wire. I have no idea what it was used for.

Now I'm told that I could pickup power at the ignition wire side of the resistor and because there is that black wire nearby which comes from the flasher, it could go on that terminal.

I did a search from generic turn signal diagram and found several so won't need one.

I'm ready to try again but want be sure about the spliced wire before I proceed.

Thanks, radar




TomO    -- 10-08-2011 @ 4:26 PM
  Radar,

It's too bad that you didn't post here before buying the harness. There are several other vendors that make good quality harnesses for the 40 Mercury. They supply both the early and late harnesses. Narragansett Reproductions, Rhode Island Wiring and Tyree Wires all have both harnesses.

The tie off point that I noticed were different were mainly under the hood.

You should not need any spliced wires to install the turn signals. If you have any, I would remove them and then when I found something that did not work, I would rewire it without a splice.

How many wires do you have coming out of the turn signal switch? It sounds like the installer was trying to use the parking lights for turn signals. If you plan to do this, you cannot use the parking lights normally.

Tom


rradar    -- 10-08-2011 @ 5:24 PM
  Well I guess the old saying: "Too soon old and too late smart," applies here! But, it looks like you have given me enough good info to finish up with the cowl loom. I'll remove the spliced wire (what an ugly piece of work) and be glad about it! Since my helper is out on an errand, I'll have put off the installation until another day. Will add the vendors names for wiring looms you mentioned to my list of sources.

Thanks for coming through guys!

Radar


TomO    -- 10-09-2011 @ 9:34 AM
  I forgot to mention that Rhode Island and Narraganset will include turn signal wiring in their harnesses for an extra charge.

Tom


EFV-8 Club Forum : https://www.earlyfordv8.org/forum
Topic: https://www.earlyfordv8.org/forum/viewmessages.cfm?Forum=16&Topic=3828