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LexTR3
04-06-2011, 05:32 PM
I want to replace my brakelight switch and the short lengths of electrical wire leading to it. The wiring chart indicates that one strand of wire is Green with Purple and the other should be Green. I know where I can purchase this wire, but what I cannot determine is what size of wire is required: 9 or 14 strands.

Can someone help me with this? Thanks.

DrEntropy
04-06-2011, 06:02 PM
More "strands" will be less prone to work-hardening failure but the real issue is gauge. #12 is the usual choice for the LBC's IIRC.

HERE'S (https://www.moparfins.com/Repairs/Electrical/Auto_basic_wiring_tips.htm) a helpful little site on the subject.

LexTR3
04-06-2011, 06:18 PM
Dr. Entrophy,


I see on a chart on British Wiring's homepage that 12 gauge US is equal to British 44 strand wire. the British wiring company rates its wire by strands, so to follow your advice, I should purchase 44 strand Green and Green/Purple wire. They have 44 strand Green, but the highest they go with Green and Purple is 28 strand.

Considering that this is for the very short connection of wire between the connector and the switch, and the Triumph chart calls for Green and Green/Purple, can I get along with using Green for both sides?

28 strands has the carrying capacity of 17.50 amps and is for horns, headlamps, and major accessory feed, while 44 strands carrying capacity is 25.50 amps, for generator, control box, and ammeter. I would think that 28 strands would be sufficient for the brakelight switch.

Geo Hahn
04-06-2011, 06:35 PM
12ga sounds kinda big (to me) for those wires. Without looking I would have guessed 16ga or so for that part of the harness.

DNK
04-06-2011, 06:36 PM
Not 12 Gauge ,way top big for that. A lot of normal wiring in the 6 was 28 strand

Geo Hahn
04-06-2011, 06:40 PM
...Considering that this is for the very short connection of wire between the connector and the switch, and the Triumph chart calls for Green and Green/Purple, can I get along with using Green for both sides?...

Ed -- my English teacher would say 'you can, but you may not'.

Years ago I bought a used (TR4) harness to harvest correct color wire as needed. I can send you a length of green/purple if you want to do it right.

DNK
04-06-2011, 06:41 PM
I might have what you need.
How long?

LexTR3
04-06-2011, 08:06 PM
Don and George,

The length to be spanned is very short: about 18 inches. But there are two wires called for in the chart. One is Green (#17 on the wiring chart), and the other is Green and Purple (#22 on the wiring chart).

I thought I'd buy a small supply from British Wiring, but I don't know either the number of strands (British) or the gauge (US) to order. I thought that 14 strand (18 gauge US) might do as it carries 8.00 amps. and is for side and tail lamps and general wiring, or perhaps 28 strand (14 gauge US) as it carries 17.50 Amps. and is for horns & headlamps, major accessory feed. The suggestion that I should use 12 gauge US (44 strand wire) came as a surprise to me.

mrv8q
04-06-2011, 08:12 PM
Maybe a purple Magic Marker might come in handy to draw a stripe on your green wire.

TR3driver
04-06-2011, 08:39 PM
Relax, Ed. 28 strand will do just fine (original was probably 14 strand).

Personally, I wouldn't even bother with using proper British wire ... just pick up some green 14 or 16 AWG at the corner FLAPS and be done with it. The electrons don't know what color the insulation is, and no one else is likely to get their head down there to check whether the purple stripe is in place or not.

TR3driver
04-06-2011, 08:41 PM
Ed -- my English teacher would say 'you can, but you may not'.

But I would say 'you can, and you may'. Meaning that it is both possible and you have my permission.

Geo Hahn
04-06-2011, 08:52 PM
I can send you 20" lengths of green & green/purple in the same gauge used originally. It is not heavy wire, could be 18ga.

PM me an address if oyu want it.

LexTR3
04-06-2011, 09:03 PM
Not knowing much about the wiring of these cars, I figured there must be some reason for the different color wires -- different gauges or something like that. Odd thing is that the manuals devote much space to all these color variations, but say nothing about the gauge of wire to use. Seems to me they should give that information so, as you say, we can just go down to the local auto store and get the right wire.

Thank you very much for the offers. George, I'll take you up on your kind offer and will send you a PM.

LexTR3
04-06-2011, 09:11 PM
Don. Thank you, also, for the kind offer. I'll have plenty with what George has offered to send me.

Randall. You've hit the nail on the head. The color on the wiring insulation doesn't concern me at all. I just want to make sure I use the appropriate "strand" or gauge for this little job.

What did I say... "Little Job." I should have learned by now that there are no "little jobs" with these cars. Chances are I will have trouble getting the old brakelight switch out because it is obviously the original switch. And, as you know, it is in a hard-to-reach place. I once had a '47 Desoto in Tucson that had a brakelight switch that was frozen in place. Mechanics couldn't budge it! I had to install a switch on the dash that I flipped on whenever I stepped on the brake to turn the brake lights on. Hope I won't have to repeat that nonsense.

TR3driver
04-06-2011, 09:31 PM
Odd thing is that the manuals devote much space to all these color variations, but say nothing about the gauge of wire to use. Seems to me they should give that information so, as you say, we can just go down to the local auto store and get the right wire.
The manuals are written from the point of view that you have a complete car and just need to maintain it. For the longer runs of wire through the harness, the color coding can be very helpful in troubleshooting.

Although I have to say that my original wiring is mostly faded to a uniform brown, and I get by just fine with a diagram, a test light, and a little cogitation.

TR3driver
04-06-2011, 09:33 PM
Nah, the original switch will come out easy. Although if memory serves, it's easier to get to by going through the wheel well, rather than down from the top. ISTR I used a small (like 8") pair of slip-joint pliers.

https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/5-wayzoom.jpg

And if it won't, there are always alternatives :laugh:

https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/DSCF0029_crop.jpg

Andrew Mace
04-06-2011, 10:01 PM
Not knowing much about the wiring of these cars, I figured there must be some reason for the different color wires...As Randall notes, it's primarily for ease of tracing circuits through the entire car. In this particular case, the main GREEN indicates switched (and fused -- thanks, Randall!) power to a unit such as the brake light switch, and the GREEN w/PURPLE indicates wire to the brake lamp(s).

Here's a useful <span style="font-style: italic">Wiring Colour Code Table</span> (https://www.dimebank.com/tech/LucasColours.html) from Chris Kantarjiev.

TR3driver
04-07-2011, 12:55 AM
In this particular case, the main GREEN indicates switched power
Switched and fused. If it was switched but not fused, it would be white. (Eg, the wire to the coil.)

Fused but not switched would be purple, but the only circuit like that on the TR3 is dedicated to the horns (and is brown/green).

DrEntropy
04-07-2011, 06:00 AM
Sorry for the confusion, Ed. The others are right, #12 would be overkill. #14 or #16 would be fine. And as long as it goes from the solid green, thru the switch to the G/P one at the harness the leads may as well be the same color. I'd do as Randall suggests and just go to the local hardware, autoparts or Radio Shack store and get a short spool of green #14 and be done with it.

ISTR seeing LBC brake switches with <span style="font-style: italic">both</span> leads as solid green at some point, too (but I misled previously with the #12 wire, sooo...).

LexTR3
04-07-2011, 06:57 AM
Back this morning...

All of this information, as usual, is very helpful, and I thank all of your most warmly.

I assumed that the various color variations were mainly for tracing the wires throuout the car. I was hoping that the color code also revealed something about the gauge of the wire to use, but that, apparently, is not the case.

The manuals are surprisingly silent on what gauge should be used for different applications. Even a manual like Martin Thaddeus' Classic Car Electrics doesn't mention gauge or strands. The only source that comes close is British Wiring's (excellent)homepage that gives the following information:

Cable size in "strands":
Cable size 9 carrying capacity is 5.75 amps
for side and tail lamps &amp; general wiring


Cable size 14 " is 8.00 amps
for same as above



Cable size 28 " is 17.50 amps
for horns &amp; headlamps &amp; major accessory feed

Cable size 44 " is 25.50 amps
for generator, control box, &amp; ammeter

British 14 strand wire = 18 gauge US
British 28 strand wire = 14 gauge US
British 44 strand wire = 12 gauge US
British 65 strand wire = 10 gauge US

Randall, As I surveyed the task, I could see that it would be very difficult to get at the switch from above unless I disconnected parts of my carburetor, so I assumed I would have to come in from below. But the placement of the switch and the location of the frame seemd to spell trouble. I hadn't even thought of going through the wheel well (an obvious choice!).

My only other question has to do with removing the switch itself. I am hoping, of course, that it is not frozen in place. Perhaps because there is so much oil and grease around it, it has been somewhat protected from corrosion. And, I assume that if it come out, brake fluid will follow it unless I quickly plug the hole or insert the new switch. I imagine that the pressure of the brake fluid on the switch creates the contact that lights the brake light.

DrEntropy
04-07-2011, 08:13 AM
The switch is hydraulicly activated, yes. Fluid will escape and re-bleeding the system is likely necessary if you remove it. Clean around the base of the switch with a small brass wire brush, lessens the chances of foreign stuff getting into the lines and allows application of some loose-juice. There should be a copper washer at the base of the switch as well, IIRC. Should be replaced. A good (and cheap) penetrating concoction in lieu of commercial brews is a 50/50 mix of acetone and ATF, shake and apply, pause and repeat. Tho it is likely you will have no issue removing that switch.

If you're quick (and somwhat lucky :wink: ) you will be able to swap the new one in and start the threads without loss of too much fluid. I'm never too lucky with getting threaded leaking things started... be aware most brake fluids will EAT paint, too. Wash/rinse the drippage with water soon after the job.

Andrew Mace
04-07-2011, 08:50 AM
In this particular case, the main GREEN indicates switched power
Switched and fused. If it was switched but not fused, it would be white....Ah, thanks for catching that. I have amended my original post, and apologies to everyone for the original confusion! :blush:

LexTR3
04-07-2011, 09:07 AM
Dr. Entrophy,

Your description give me a clear idea of what I will encounter when I tackle this "little job." Once again... many warm thanks.

I'm not reluctant to bleed the brakes after doing this procedure, but if I'm quick -- as you say -- and lucky -- I should be able to get the new switch started in little time. The amount of fluid that leaks out should easily and immediately be replenished from the resevoir, so it seems to me that no air should get into the brake line. If that sounds too optimistic on my part, however, let me know and I will plan to bleed the brakes after putting in the new switch. I would, of course, test the brakes after the switch is in but before bleeding to see if they are soft.

What led me to this plan to do this "little job" was not a malfunctioning brakelight switch, but some pretty scruffy looking wire leading from the snap connectors to the switch. I began with the simple of idea of replacing the wires, and then moved on to the idea of replacing the wires and the switch. I may just clean up the switch, leave it in place, replace the wires, and wait until the switch fails (if it is going to fail).

TR3driver
04-07-2011, 09:17 AM
There should be a copper washer at the base of the switch as well, IIRC.
Usually that would be true, but in this case the threads are tapered pipe threads, so no washer used.

What I did to limit the amount of fluid lost was to prop the brake pedal slightly depressed, just enough to close off the valve in the MC. I have a carpenter's bar clamp that is turned around backwards to make an adjustable spreader; but you could probably just trim a piece of 1x2 to length. Result was I only lost a drop or two of fluid, even though it took me some time to swap the switch. Best of all, I didn't need to bleed afterwards.

While cleaning wouldn't hurt, personally I wouldn't use penetrating oil. The fitting is brass, so corrosion shouldn't be a problem. And I wouldn't want to risk getting penetrating oil into the braking system where it could eventually attack the seals.

I use DOT 5, so no worries about damage to the paint. But from what I've seen, DOT 3/4 will do significant damage even if you wash it off immediately; so it would be best to put some sort of barrier (maybe plastic plus a shop rag) under the switch.

DrEntropy
04-07-2011, 09:17 AM
What led me to this plan to do this "little job" was not a malfunctioning brakelight switch, but some pretty scruffy looking wire leading from the snap connectors to the switch. I began with the simple of idea of replacing the wires, and then moved on to replacing the wires and the switch. I may just start with the wires and wait until the switch fails (if it is going to fail).

The slippery slope of: "might-as-well"! :jester:

...it can snowball into a complete resto project. :wink:

I'd go with: replace the wires... then drive it!

Andrew Mace
04-07-2011, 09:44 AM
I'm not reluctant to bleed the brakes after doing this procedure, but if I'm quick -- as you say -- and lucky -- I should be able to get the new switch started in little time. The amount of fluid that leaks out should easily and immediately be replenished from the resevoir, so it seems to me that no air should get into the brake line.A little trick that might help: put a bit of "Saran Wrap" or similar clingy plastic wrap over the filler of the reservoir, then replace the cap not quite tight. The Saran Wrap might help to keep the fluid flowing down. Not much of a difference usually, but it helps. But do take the Saran Wrap off once you're done! :wink:

Oh, and I've swapped a couple of those switches out without having to rebleed.

Good luck!

LexTR3
04-07-2011, 11:46 AM
Randall, Dr. Entrophy, and Andrew,

Good, useful information. Many thanks.

Randall: I'm not sure I understand how the "propping the brake pedal slightly depressed" works, but if it does, that's good enough for me." What is the "MC"? What holds your spreader -- or the 1/2 -- in place to hold the brake pedal down? (extended to the seat or dash?) And how much is "slightly depressed"?

I'm afraid I just can't picture it in my mind.

I'm still leaning to replacing the wires and letting it go until the switch dies, but then I'll know how to replace it, thanks to you'all (or, as they say her in the South... ya'll.)

Andrew Mace
04-07-2011, 12:03 PM
Hmmm, something just occurred to me: Does the "apparently original" switch still function properly? If so, I suggest leaving it there. I have heard that, like so many other bits, currently available replacement switches aren't nearly as good. Wires? Sure, especially if they've gotten brittle or otherwise damaged. Otherwise, <span style="font-style: italic"><span style="font-weight: bold">if it ain't broke....</span></span> :driving:

LexTR3
04-07-2011, 12:16 PM
Andy,

As far as I know, the switch is still functioning properly. In fact, I began all this by thinking that I would only replace the wires, which are very ratty and brittle. One thing led to another (Dr. Entrophy's warning!) and I began to think that I might replace the switch while I was at it. And although I am glad to know how to replace it, thanks to all the good advice I've received, I am -- indeed - inclined to leave the switch alone until it dies and only replace the wires.

I have to admit that I am replacing a lot of stuff on my car -- in the name of preventive maintenance and aesthetics -- but not everything. I, too, have heard that a lot of reproduction stuff is not as good as original stuff, so I am moving very carefully.

TR3driver
04-07-2011, 12:49 PM
Randall: I'm not sure I understand how the "propping the brake pedal slightly depressed" works, but if it does, that's good enough for me." What is the "MC"? What holds your spreader -- or the 1/2 -- in place to hold the brake pedal down? (extended to the seat or dash?) And how much is "slightly depressed"?
MC is master cylinder, the brake master cylinder in this case. With the pedal fully up, there is a valve inside the MC that allows the brake fluid to pass between the pressure pipes and the reservoir. (Very important that this valve be open during normal driving, as otherwise the brakes will bind when the fluid gets warm.) As soon as you step on the brake pedal, though, the valve has to close so you can build pressure in the system.

How far the pedal has to be pressed to close the valve probably varies with how loose your linkage (and adjustments if any) are, but it shouldn't take more than maybe 1/2" or so. On my car it's only about 1/4". This is the zone that feels like free play before the brakes start to move.

My 'spreader' originally looked somewhat like this:
https://ecx.images-amazon.com/images/I/41KC0GCFXYL._SL500_AA300_.jpg
but I drilled out the rivet that holds the fixed jaw to the bar, and reversed both jaws. (Used a bolt to replace the rivet, so I can switch back if needed.) I just put it through the steering wheel, with the end resting on the brake pedal, then slid the moving jaw up against the wheel. It's an old service trick, I can't claim credit for thinking of it. (Probably came from Popular Mechanix or some such.)

LexTR3
04-07-2011, 01:16 PM
Randall, Great idea. I will file it away for when I decide to replace the brakelight switch. I have several of those clamps and can modify one for this purpose. A neat trick. I hope you'll include it in the book I have been encouraging you to write!

One thought on "If it ain't broke, don't fix it." Generally, I agree, and I certainly have found that "fixing" something that didn't need "fixing" sometimes led me to a much larger project. But with this car... in great shape but 50 years old and having had several POs "tinker" with it ... a number of times when I began looking at something that didn't appear "broke," I found that indeed it was "broke." Take for example, my carburetor. It was functioning fine, but I decided to replace a jet lever and some other parts. Only then did I find that the last guy who worked on the car left off three strategic cotter pins! And when I decided to change the oil in my O/D... though it didn't need it... I found that the last guy who had worked on the car had forgotten to tighten the O/D drain plug! So, I have mixed feelings about all this.

TR3driver
04-07-2011, 01:45 PM
So, I have mixed feelings about all this.
It is a fine line, no doubt. But the prevailing tendency seems to be what some know as "Shipwright's disease". I know people who literally started out just to change the engine oil, and wound up doing a full frame-off restoration! And of course some of them never finish the restoration.

And as noted, many replacement parts are dubious. This timing sprocket had less than 7,000 miles on it:

LexTR3
04-07-2011, 02:07 PM
Randall,

You are right, it is a fine line. I guess the "safest" approach is to carefully inspect everything that you can, within reason, to make sure it "looks right" or "sounds right" or is "acting right." If it doesn't seem right, then consider "fixing it." But if it looks right, then leave it alone.

The exception to this is routine maintenance (periodic valve adjustment) and replacement of points, plugs, lead wires.... things like that.

I went beyond this to replace my old starter with a high torque starter, installed a new generator, replaced my old radiator with a new aluminum radiator, new water pump, timing chain, clutch, etc. -- while the engine was apart for rebuilding. Those old items would have continued to serve, but the engine was out, so I decided it was a good time to do this other work.

Geo Hahn
04-07-2011, 03:29 PM
I agree that if the old switch is fine it may well be better than the available new replacement, however: in my case the switch did not suddenly fail but rather it took more and more brake pedal pressure to activate it. The result was that I would frequently come to a complete stop w/o the brake lights coming on -- yet if I pressed the pedal to test them they would illuminate.

So as part of your decision whether to replace the switch you might consider how easily it operates.

LexTR3
04-07-2011, 04:05 PM
Hi, George,

That's a very good point. I have not checked it that closely and should do so. I have not installed an auxiliary stop light, like yours, so I need to make sure that my brake lights are working.

Thanks for the idea.

Hope you got my PM. I'm not very experienced in sending PMs.

TR3driver
04-07-2011, 04:56 PM
That's a very good point. I have not checked it that closely and should do so.
Easy way to check : with the key on but the engine off, watch the ammeter as you press the brake pedal. The brake lights present a very definite discharge. With experience, you can even tell the difference between one and two.

It's tougher to see with the engine idling, but still there.

BTW, I agree entirely with George. I had the same exact thing happen, enough times that I got disgusted and converted to a mechanical switch. The dang switch should last at least as long as the bulbs!

DrEntropy
04-07-2011, 05:47 PM
mehheh.

As a "light check" routine I will go to a shopping plaza with business frontage made of glass, top to bottom. Easy to see the reflection of your lights in the window! One man operation. :wink:

LexTR3
04-07-2011, 06:38 PM
Dr. Entropy,

Ha... Ha... That's exactly how I check my lights, blinkers, and stop lights!

I think I'm OK... So I'll stick with my original plan: to replace the wires from the snap connectors to the switch, clean the switch a little, and watch for any failure of the switch.

I've learned a lot from this thread. Many thanks.