New TR4A Wiring Harness

[My Dads Car]

I’ve read somewhere “there are no atheists in fox holes.” I’m beginning to think the same could be said for those of us who work on the electronics of these cars… I knew this part of the restoration would be tough but some intervention, divine or otherwise… is definitely necessary!  
 

For reference I’m working on a LHD car, new harness from Moss - I went with the black tape version. No overdrive. 
 

First question (of many to come): wiper motor switch. I’ve seen several diagrams online as to how to connect this specific switch, but still remain a bit confused. Can someone explain what wire goes to its specific numeric contact?

Next question: here’s a view of the lighting wires coming out of the loom. The schematic doesn’t say anything about a double blue/white (aka UW) in this area. These colors are associated with the headlights but I was able to get them going (both hi and low beam) without connecting it. Even more interesting is that when tracing this connection for continuity it seems to be connected to the B terminal on the flasher…

Any thoughts 

Finally, (for now… )The heater blower won’t work. I know it’s ok, as a direct connection to the battery makes it come to life. However, when I try to connect/activate it through the switch I get nothing. When checking continuity for this I get the proper green wire at the voltage stabilizer and fuse box, but I also get continuity to earth both on the body and at the voltage regulator. There shouldn’t be power and ground on the same wire- right?
 

Thanks in advance for all help! 
Jamie 

[RogerH]

Hi Jamie

for the switch   #1 & 7 are black.  They are linked inside so only need #1 connected.

#4     is Green/brown   (G/N)

#8   is Green/Red  (G/R)

this  will cause the the wipers to come on fast with the first click - that is correct.

The second click on the pull switch will slow them down.

There is a mysterious way to make them come ON slow with the first pull.  Get them working firstly.

 

Roger

[Nigel C]

Roger, is that mysterious way already built into the switch you sent me?😀

[RobH]

Jamie - just a guess,  that double blue/white may be the connection point for the dashboard high-beam bulb.  The two wires you see could be  power in from the dimmer and power out to the high beams.   The connection should measure 12V, only with the high beams on.    

(The position and orientations of junctions shown on the schematics may not be exactly as drawn, though the actual connections are right of course.)  

I don't know what type of meter you are using to trace the connections, but the apparent link to B on the flasher may just be a 'back-feed'  path through the lamp filaments and grounds rather than an actual direct connection.  You can really only do meaningful tracing with both  ends of the wires disconnected from everything else.  Once you start connecting it up there are odd paths measurable which just confuse.

 

Just for information, the switch you show is a Lucas 34477  

The connection pattern for that is

Position 1 ( in = off ), terminals 1,6 & 7 connected

Position 2 (middle = fast), terminals 1,4,6 & 7 connected

Position 3 (fully out = slow), terminals 1,4,7 & 8 connected

 

Edited April 14 by RobH

[My Dads Car]

49 minutes ago, RogerH said:

Hi Jamie

for the switch   #1 & 7 are black.  They are linked inside so only need #1 connected.

#4     is Green/brown   (G/N)

#8   is Green/Red  (G/R)

this  will cause the the wipers to come on fast with the first click - that is correct.

The second click on the pull switch will slow them down.

There is a mysterious way to make them come ON slow with the first pull.  Get them working firstly.

 

Roger

Thank you, Roger - I had it connected wrong...!

8 minutes ago, RobH said:

Jamie - just a guess,  that double blue/white may be the connection point for the dashboard high-beam bulb.  The two wires you see could be  power in from the dimmer and power out to the high beams.   The connection should measure 12V, only with the high beams on.    

(The position and orientations of junctions shown on the schematics may not be exactly as drawn, though the actual connections are right of course.)  

I don't know what type of meter you are using to trace the connections, but the apparent link to B on the flasher may just be a 'back-feed'  path through the lamp filaments and grounds rather than an actual direct connection.  You can really only do meaningful tracing with both  ends of the wires disconnected from everything else.  Once you start connecting it up there are odd paths measurable which just confuse.

Hi Rob, thank you for the reply.

I forgot to mention the engine is out of the car, so open circuits on generator, coil, distributor,  starter... also no lights other than headlights including the instrument lights. I bridge the ammeter wires and make sure the ignition (which is fully connected) is switched on. There is a Blue/White wire on lighting switch steering column: the schematic is confusing as it shows the indicator wire coming from the dipper switch, not the column.

I am using a decent quality multi-meter to test these wires, using it as an ohmmeter with an audible beep when there's continuity (with the battery disconnected).  I was wondering if there was such a thing as "back-feed" with all the various connections.  

Jamie

[RobH]

7 minutes ago, My Dads Car said:

There is a Blue/White wire on lighting switch steering column:

Just to throw in more confusion - I have heard tales of differences in the wiring colours around the flash-to-pass connection on some cars.  The Advance Autowire schematic shows blue and brown/blue there  but I believe some people have found blue/white instead.   I think that may depend on whether the switch is original  or an after-market  replacement though. 

[My Dads Car]

OK - you have all been extremely helpful so far, thank you very much!

Here's where I stand now:

https://youtu.be/ZMIXYfPf4u8

So close, yet so far... Anyone have any experience with this?

Thanks again- Jamie

[RogerH]

4 hours ago, Nigel C said:

Roger, is that mysterious way already built into the switch you sent me?😀

Yes.

[NigelC]

 😍

[My Dads Car]

On 4/14/2026 at 9:52 AM, RogerH said:

Hi Jamie

for the switch   #1 & 7 are black.  They are linked inside so only need #1 connected.

#4     is Green/brown   (G/N)

#8   is Green/Red  (G/R)

this  will cause the the wipers to come on fast with the first click - that is correct.

The second click on the pull switch will slow them down.

There is a mysterious way to make them come ON slow with the first pull.  Get them working firstly.

 

Roger

Hi Roger,

The switch works, but in reverse!

Switch pushed in = fast

Pulled out 1 lick = slow 

Pulled out 2nd click = off

Any ideas? Could the cause of this be related to my lighting switch turning off all electronics in "off" position? I just realized my wiper motor and heater fan are working with the ignition key in the "off" position... I don't recall that to be the case when I drove the car last.

Thanks- Jamie

[RobH]

You obviously have several wires connected to the wrong terminals on the switches - maybe both on the ignition circuit and the wiper switch.  Sometimes it is not obvious which terminal the number refers to. 

If the wipers and heater are working with the ignition off, the 'green' circuits are obviously live which is wrong.  It could be the feeds have been swapped over at the fuse-box.  The green wires should be fed by the white wires via a fuse but it is possible to muddle the wires on the lightswitch and get a feed from there.  If you pull the fuse out but the voltage is still there, it is probably a wrong connection at the light switch.  

[RogerH]

Hi Jamie

follow what Rob has posted first.
The info I posted above is correct.  Make sure you have used the correct numbers on the wiper switch (I'm sure you have)

Roger

[My Dads Car]

1 hour ago, RobH said:

You obviously have several wires connected to the wrong terminals on the switches - maybe both on the ignition circuit and the wiper switch.  Sometimes it is not obvious which terminal the number refers to. 

If the wipers and heater are working with the ignition off, the 'green' circuits are obviously live which is wrong.  It could be the feeds have been swapped over at the fuse-box.  The green wires should be fed by the white wires via a fuse but it is possible to muddle the wires on the lightswitch and get a feed from there.  If you pull the fuse out but the voltage is still there, it is probably a wrong connection at the light switch.  

Eureka! That did it. I had white going to red at fuse box... Rookie mistake. Thank you very much for the help.

Wiper switch still reversed, I will take a deeper dive on that asap. I probably have the contacts confused there as well...

Thanks again- Jamie

[My Dads Car]

Update: soooo close! Here's where I stand:

• Heater fan = good
• Wiper motor = good at both speeds
• Running lights = good
• Headlights = good (both hi and lo beam)
• Turn signal = grrrrr..... kinda' works. (Full disclosure: I am not testing the turn signal with the actual lighting assemblies in place as I do not have them at this time. Instead, I am using old dash lighting bulbs, with their attendant typical sockets as testers connected by bullet connections into the loom.)

The left side functions properly, including flasher! However, the right side lamps light but don't flash. I have read the flasher is very sensitive regarding current draw to function properly, could I be under-loading the flasher on the right side. Also, I seem to have continuity between the U/W (blue/white) wires under the dash and the X (B) terminal on the flasher- is this supposed to happen? The same terminal on the flasher also seems to connect to earth as well...

Jamie

[Ralph Whitaker]

Hi Jamie,

yes the flasher unit usually requires 2 x 25w bulbs to work correctly. If one bulb blows then the remaining bulb flashes very slowly if at all. I say usually because if the car has a modern electronic flasher unit, of the type neccesary for LED bulbs, they are not load sensitive and will flash whatever the load. If one side lights and flashes but the other side lights and does not flash it would seem that there is too low a load on that side. I would wait until you can wire up the correct 25w bulbs each side before looking for a problem that may not exist.

As an aside, a lot of US cars use an interrupter in the brake light circuit as the rear flasher, I don`t know whether that was the case with imported TRs.

Also double check for good earths.

Ralph

Edited April 20 by Ralph Whitaker

[RobH]

I think your odd 'continuities" are due to the meter and the way you are using it Jamie.    There will be a tenuous conductive path  from the white/blue wire through the headlamp bulb filament to earth and then back up through the flasher bulbs to the flasher unit itself.   You will find similar devious paths all over the car on every circuit that connects to earth (chassis).  They don't signify a problem since in reality current stops when it gets to earth and just goes back to the battery, it doesn't flow up the other circuits.    

Odd resistances to earth will be through lamp filaments or motor windings. 

 

 

Edited April 20 by RobH