General Tech Fix, replace or rewire?

[mailbox]

I've got a 76 TR7 that I'm slowly putting back together. I trying to figure out which is the best way to "fix" the old wiring harness. When I pulled the harness, it had several wires that obviously "had no smoke left in them". I'm not sure which ones are damaged as I haven't gotten that far into it just yet. My question is should I try to fix the original harness, replace it with a new harness or simply rewire the whole thing from scratch? Fixing it would be the cheapest, but I can see big problems in the future from nearly 40 year old "Lucas" wire. Replacing would be the easiest, but cost the most. Rewiring seems to be the best option, but my skills with wiring are......um.....not great. I would appreciate any insight into this that you can give me. Thanks.

 

[TR3driver]

I'm probably in the small minority here, but I've always patched up the old main harness, adding wires as necessary. In fact, I recently reused some of the original wire that came out of my 59 TR3A, just to get the right color codes as I added headlight relays to my current 56 TR3. It still has it's original harness as well, even though the color codes are basically nonexistent by now (except in the areas where the DPO cut the original harness to move the turn signal switch to the dash).

But no matter which way you go, you're going to have to brush up on those skills, IMO. Even with a new harness, there will be lots of connections to be made, and lots of troubleshooting to be sure you've got it right.

If you've already got the old harness out, and it is damaged as you say, then I'd probably spring for a new harness. Of course, the next question would be whether that should be a reproduction stock harness, or the AAW upgraded one. The AAW is more of a kit, so there is more work (maybe that's what you meant by "rewiring from scratch"), but it's a very well made kit with properly color-coded wires and much better quality wire than original. I also like the idea of being able to customize it to suit your needs and tastes. Unless it has changed since Dan retired, it doesn't use that PVC insulation that smokes if you look at it cross eyed but good teflon that won't even melt until well over 500F. Dan (the founder of AAW) used to work as an electrician in a nuclear power plant and it shows

 

[Geo Hahn]

A new wiring harness was one of the nicest things I did for myself when I had the car apart for a respray -- but then my wiring was a bit of a nightmare with non-standard colors, wires to nowhere and sloppy crimp connections:

So much more pleasant to work with a correct harness -- makes diagnosing and modifying very easy:

FWIW - I used the stock harness sold through Moss (though possibly supplied by somewhere else).

 

[mailbox]

I looked into AAW. Thats the way I thought I might go until i found out they don't make a TR7 kit. I was hoping to rewire the car kinda like a hot rod, but that might be above my skill level. Some have said it was easy to build a harness, but they didn't say how much know how they really have.

 

[George_H]

British wiring has harneses. https://www.britishwiring.com/category-s/74.htm . But I would fix whats bad and move on.

 

[dklawson]

I like the modern insulation but I don't like working with Teflon jacketed stuff. It is stiff and hard to strip. It is good for high temperatures but if your fuses blow when they are supposed to you won't need that high temperature rating.

With the Mini I installed a new harness as it was badly damaged and all the colors had faded. When I worked on the GT6 and Spitfire, I patched and added wires as Randall suggested. Britishwiring.com linked above can provide you the correct wire in the correct color codes if you opt to repair rather than replace. I

cannot say anything about the AAW kits as I have no experience with them. However, my acquaintances in the U.K. regularly discuss the high quality work of AutoSparks. They make harnesess (including custom ones for the end user) for just about any British car you can imagine. They do not list a price for the TR7 harness but encourage you to contact them. I assume that is not because it is high-priced but because of the number of options they can offer. It would not surprise me to learn that they make the harnesses for some of the usual vendors we deal with over here.
https://www.autosparks.co.uk/index.php

 

[mikephillips]

My personal preference, and what I've done in my cars, is to replace with a new harness. I've gone stock in all cases since I never intended to add modern devices and change the load on the harness. I know guys who have used Painless brand wiring kits in other cases to add more capacity and fusing. You need to know what you want to be able to do to decide. replacement with new to me makes sense since old wires can have the insulation crack around the individual wires where the harness has been bent which could lead to shorts and knowing if this has occurred inside the wrapping is pretty much impossible

 

[TR3driver]

I looked into AAW. Thats the way I thought I might go until i found out they don't make a TR7 kit.

Sorry, somehow I missed that you were working on a TR7.

Doing it right is a lot of work, IMO. If you just want to make it run, that's not so hard

First step in building your own is to come up with a detailed wiring diagram. You'll probably start with one of the available factory diagrams, but then you'll have to at least make sure it matches your car. I don't have any experience with a TR7, but I know that for a TR2-3 there are at least 6 or 7 factory wiring variations that are not particularly well documented. Most references only give one; and if you follow that one with most cars, the fuse pops as soon as you turn the key on. The Stag is somewhat better, at least more of the variations are documented; but still the most common one is not in any of the books (as far as I know).

You may also want to add some features like relays for high current loads, more fuses, maybe a fusible link here or there. Maybe a headlight reminder? Cruise control?

Now you create that wiring, with (hopefully) suitable color-coded wires, and check it all out. Again I don't know about a TR7, but on my TR3 & Stag there are a lot of permanent connections to be made (for example the bulb holder for the high beam indicator is soldered directly to the harness). The Stag also has several harness connectors that, while they may not be absolutely required, sure make it easier to do things like remove the center console, instrument panel or steering column.

Once that is done, you can take it back apart to wrap it or (better yet IMO) install sleeving. There are of course sleeving designs that don't require removing the wire from the car, but they look incredibly cheesy to me.

 

[glemon]

I actually guess I am in the small but now slightly larger minority with Randall, I have never replaced the wiring harness on any of my cars, even my TR250, which most everything came off of. I suppose if I could snap my fingers and have a new one I would do it, but it just never rose to the priority level where the time and money seemed worth it to me. The wires themselves are pretty sturdy and reliable, and can be tested for continuity, it is usually the bullet or spade connectors that cause trouble, and they can be cleaned and reused, or replaced as needed. Over the years I have come to learn a bit of the lucas wiring color coding, and so do like to keep the stock color, a spare harness from a rusted out car, or one discarded from those whose school of thought is replace the things, is just a great item to have, you can replace wire or wire up an option like an overdrive with the right colors and connectors, and replace connectors with the right type when things get broken, lost or corroded beyond repair.