Thoughts on Restoring a Morgan
Installing New Wiring Harness

©By: John T. Blair (WA4OHZ)
dot_clear 1133 Chatmoss Dr., Va. Beach, Va. 23464; (757) 495-8229

Originally written: April 1998

Last update: June 18, 2009

The following is the letter I wrote to British Wiring after installing their wiring harness in my '65 4/4 Morgan. The letter details the "lessons learned" from this job. Removing the old harness took less than 4 hours but installing the new harness took almost 5 days!!!

April 25, 1998

British Wiring
20449 Ithaca
Olympia Fields, IL 60461
(708) 481-9050

Dear Edwin & Lesley Cehelnik

I assume that I talked to Lesley on Friday March 27. Thanks so much for returning my phone call. I purchased a MN12c wiring harness for my 65 Morgan 4/4 from you all back in March of 97. I finally got the time to install it, so far I’ve spent the better part of 4 days installing just the front main wiring harness due to the differences between the 4/4s and the +4s. All in all I found the harness to be of excellent quality and workmanship. I thought I’d pass along some of the “lessons learned” during this installation. Several of these items you might want to pass to your supplier as I feel it would make this harness even better. I don’t know if they would make the changes that I’m suggesting but it would help the installation in a 4/4 quite a bit and would not hurt the +4 installation. Feel free to include a copy of this letter to anyone that purchases one of your harnesses for a Morgan of that era if you think it would be of any value. A copy of a wiring diagram would also help. I can send you a copy or have your clients contact me.

All of the following comments pertain to the front Main harness.

1. There is a break-out just after the break-out for the voltage regulator and fuse block. This is the left side wiring subharness. On this section there is a break-out of four more sub harnesses:
dot_clear a. One for the horn,
dot_clear b. One for the head light dimmer switch,
dot_clear c. One for the left side front lights,
dot_clear d. One for Stop light switch branch.

These all split at one point. They are supposed to be routed back into the firewall and run across the inside of the cockpit. The hole in the firewall is 7/8” dia. However, taping this “fork” and trying to compress it as much as possible I could not get it any smaller than 1 3/8” in the largest dimension. Thus I was forced to elongate the penetration hole in the firewall to get the harness through. Now I must fabricate some type of cover to hide this modification.

I would suggest that these 4 break-outs be staggered over a couple of inches to allow the harness to be worked through the 7/8” diameter hole in the firewall. This would not change the function or length of wire required.

2. The coil on a 4/4 is mounted on the right side valance (inner fender panel) as compared to the coil of the +4 being mounted on the engine block. On a 4/4 the white ignition lead to the coil is several inches too short to be dressed with the front lighting run.

I would suggest that this lead be shortened to about 3” where it breaks-out of the loom and be terminated with a bullet connector. Then two extensions could be made, one for the +4 and one for the 4/4s. One end of each extension should be terminated with a bullet and a barrel connector and the other end be terminated with the 1/4” female spade as it currently is.

3. The two generator leads are currently terminated with female spades and are broken out of the harness where they should be for the +4. The generator on the 4/4 is on the left side of the engine so an extension is provided. However, it is not long enough to be dressed back down the valance, into the cockpit, across the car, then out the firewall and along the valance to the generator. I cut this extension in two so that there was enough loomed wire to be dressed in the engine compartment. I put bullet ends on all of the cut wires and installed an extension in line with barrel connectors under the dash.

Another problem with the extension was that the yellow/green wire is terminated at both ends with a eye lug and could not be attach to the male spade on the generator or into the female spade in the original wiring harness. I had to replace one of the eye connectors with female spade to connect to the generator, and a male spade at the other end to attach to the original wiring harness. (Note - I probably should have routed this as they indended, up to the front towards the Radiator and across the crossbrase and back to the generator. Unfortunately, I had the original harness in mind and went that way.)

I would suggest the following changes:
dot_clear a. This extension be extended by at least 36 inches.
dot_clear b. The current extension has a female spade on both ends of the large yellow wire. The smaller yellow wire has a 1/4” female spade on one end and a small eye lug on the other. The original generator break-out has 2 female 90deg. spade lugs. Consequently, the extension cannot be attached to the 2 female connectors in the harness. I would suggest that the connectors on one end of the extension be replaced with male spades to mate with the female connectors currently in the harness. One the other end, the eye lug should be replaced with a female spade so that it is the same as the original break-out and fits the generator.
dot_clear c. I might also suggest using inline spades as opposed to the 90deg. spades that are currently used.

4. The green/blue wire for the temperature sending unit is broken out of the right side subharness with all the wires for the voltage regulator. The 4/4 needs this wire on the left side of the car. I routed it back into the cockpit with the left side break-out, ran it across the cockpit and out the left side hole in the firewall. However, it was too short to reach the sending unit. I had to do the same thing I did with the generator extension, cut it and splice in about 24” under the dash. I attached the end with the eye lug to the temperature sending unit, and dressed the wire down left valance with the left wiring harness and back into the cockpit.

I would suggest that this wire’s break-out position in the harness be moved back so it is inside the cockpit. Then provide two extensions of different lengths, for either the 4/4 or the +4.

5. After finishing the installation of the front harness, I tested the electrical system for shorts. None! It was time to apply power. NO SMOKE!!! What a relief. Now lets start checking systems out.
dot_clear 1. Ignition - the car started!!! Big shot in the arm.
dot_clear 2. Headlights worked
dot_clear 3. Turn signals worked.
dot_clear 4. Stop lights worked.
dot_clear 5. Running lights - NO work.
dot_clear 6. Dash lights - NO work.
dot_clear 7. Horn - NO work.
dot_clear 8. Wiper motor - NO work.
dot_clear 9. Generator - NO work - haven't finished making the extension.

I spent about 5 hours (with an Ohm meter) troubleshooting and fixing the circuits that didn’t work:
dot_clear a. The problem with the running lights and the dash lights turned out to be wire connected to the wrong switches. There are several Red wires under the dash. Non are labeled. I had inadvertently connected the wrong red wires to the wrong switches.

dot_clear I would suggest that these red wires be tagged with a label of some sort to make it easier for the customer.

dot_clear b. The problem with the horn and wipers turned to be: their ground wires were not grounded. Both of these items switch the ground wires.
dot_clear i. The horn ground wire has a spade on it instead of an eyelet. I will have to replace this spade with an eyelet.
dot_clear ii. The wiper motor ground (once found) has a very small eyelet on the end of the wire. Too small to attach to any of the bolts under the dash. I had thought that this wire had something to do with the instruments based on the size of the eyelet. I have to replace this eyelet on with a larger one. In addition, this wire is only about 3" long and will not reach any of the bolts that act as grounding posts. I will have to extend it this wire also.

dot_clear I would suggest that the ground wires for the horn and wiper motor be tagged with a label of some sort to make it easier for the customer.

dot_clear c. There were several grounds still left unconnected under the dash. Most of the ground wires have eye lugs on them for attaching to bolts under the dash for ground points. However, there are several with 1/4" female spades on them and nothing under the dash to accept them.

I hope these problems are clearly stated. While they were an inconvenience, they were not insurmountable. The worst part was having to enlarge the hole in the firewall. Hopefully these comments will help others installing the harness in a 4/4 (and possibly a +4) and that your supplier will think about making the suggested modifications to his harness.

Even with these problems, the harness was competitively priced and worth the money.

dot_clear Sincerely

dot_clear John T. Blair

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