• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
  • When posting a classified ad, you MUST select a prefix from the drop-down next to the subject line. If you don't you will get an error and your ad will not be posted!
Tips
Tips

TR2/3/3A TR3A wiring

Share this page

tmc

tmc

Senior Member
Offline
I'm about ready to start re-wiring my TR3A project. I have "complete" wiring harness from Moss. I labeled some critical wires from the old harness, but it was such a mess that using it as a guide seems unlikely (lots of splices). My plan was to lay it out "on" the car and by using the wiring diagram I have figure out what goes where. I have pictures of the major multi-connection spots to go by as well.

Any advice from the experienced rebuilders out there? I am an OJT auto restorer.
 
All you need is a good BIG wiring diagram, The bigger the better to see where all the wires go. It's tuff getting older!
 
The color coding on the diagrams are pretty straight forward. Just be careful in the front of the car ie: flashers, parkings because some wires I believe need to be connected together on on side to energize the other side.

Good Luck
 
I seem to recall that the Terrianne website has a diagram of the bulkhead holes and where the wires go thru. The color coding really does help. It also seems to me that the diagram I used from an TRF TR3 book was for a RHD car.It just takes a bit of patience. You will end up with one wire left over in the front though I can't recall which side since the harnesses are for both RHD and LHD. FWIW I started with the rear of the car and then worked it thru the bulkhead.

Have fun

Gary
 
Make sure you get a wiring diagram that is appropriate to your car and the harness you got. Most sources show only one or two different diagrams, but there were at least 6 distinct varieties, not counting RHD vs LHD.

Here's one that seemed to match my 58 TR3A (TS39781LO) pretty good. I doctored it up to show the LHD connections (but the instrument panel area still shows the gauges in the wrong locations).
https://i258.photobucket.com/albums/hh260/TR3driver/TR3ALHDSCHEMATICMODIFIEDFROMPRAC-1.jpg
 
Aloha,

If any of the bulkhead grommets where the harness passes through are suspect, now is the time to replace them as you install the new harness. The Moss Motors catalog has an illustration of the various grommets and blanking plugs on the bulkhead. Also, I would recommend you salvage lengths of good wire from your old harness. These pieces come in handy when you add accessories like an electric cooling fan, need additional grounds and those small bits that the harness doesn't include. ISTR that you may need some red with white tracer for gauge illumination lights, white with black tracer from the coil to distributor and probably a few others. If you do have any electrical accessories installed, I recommend you add a diagram of those connects (include wire colors) to your standard wiring diagram. That may come in handy in the future for you or the next owner.
 
I have always found that the stock wiring schematics from Advanced Auto Wire, much easier to read then the ones furnished by Triumph.
 
When I got a new harness (also Moss) for my TR3A I laid it out on the floor in the shape it would have in the car then made my own wiring diagram using the actual harness as a source and a correct wiring diagram for reference. When I was done I knew I had accounted for every connection including those that adapt a 'universal' harness into one for LHD.

As noted -- however you approach it you want the right diagram for your car, in particular the wiper switch and motor had wiring variations that if not correct will surely produce some smoke.

You may also want to search the archives ('Use the search, Luke') to find out about some fuses that you may want to add or even relays and fusible links.

Careful, even methodical is the way I approached it and everything worked perfectly first time and ever since.
 
tinman58 said:
All you need is a good BIG wiring diagram, The bigger the better to see where all the wires go. It's tuff getting older!
Click to expand...

Howdy Folks,

I just bought a "BIG" (Really BIG) wiring schematic on ebay for $15.00 + shipping. You may want to check it out as the seller had a great idea in exploding the "Miniature" ones in the catalogs. He has schematics for TR2,3,3A & 4s.

I should be rec`g. mine in a few days & I`ll let you folks know what I think about it. Looks really nice & "BIG" in thier listing.

Russ
 
Gotta do mine to this winter too. The Dpo replaced all the wiring with red wire. Although the gauge is a bit thicker which is generally good, it's a royal pain to trace the wires. Got to do it 1 wire at a time. So I have been putting it off. I have a complete new harnes for britishwiring.com - really nice.
 
Different strokes and all that. The original harness on my 56 is faded to complete illegibility, and the DPO had even cut off a number of the bullets; but it seemed easier to me to just "ring out" whatever I need to know than to hassle with trying to replace the whole thing. Only took an hour or so to get everything working as it should (except the wipers I didn't bother to install, and the heater I removed permanently).
 
Thanks for all the comments! I will look for the bigger wiring diagram.....old eyes........lay out the harness on the floor........be patient........methodical.......sounds like fun! Good winter day's (week's) project. I have all new grommets, blanking plugs, etc. already. No accessories, except the heater. Good idea to leave notes for the next owner.

I'm almost inspired to attack it today......almost.
 
I do not know your commission # and thus do not know whether you are working with Lucar (spade) connections or the earlier screw terminals. If the latter you may want to strip the ends and tin the tips while the harness is loose and it is still an indoor winter project.

When I did mine I did not shorten any wires at the time of the install -- the control box (aka voltage regulator) in particular had much longer leads than needed. I lived with the excess for a year or so before I got brave enough to trim them to minimal length. I say 'brave' because they look better shortened but you can always shorten a wire, hard to make it longer once it is cut.

TR3ControlBox%20before.JPG


TR3ControlBox%20after.JPG
 
Back
Top