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July 16, 2016

Exterior Light Assemblies

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Front Marker Lights
Front Signal Lights

I'm still mainly working on getting body panels in shape, but this involves test fitting some of the larger lighting assemblies like head and tail lights.  To make sure these assemblies are in final form, I decided to take a branch and get all the outside lighting up to snuff.

Tail Light Assemblies

On the TR6, a single tail light assembly carries the tail, stop, reverse, and turn lights, as well as a side marker light.  It is a very clean looking unit with separate lenses of appropriate color that fit together to look like a single lens with multiple colors.  My lights had 40 years of grime on them and one of the lenses was broken, but they were otherwise complete and intact.

The heart of the assembly is a chrome plated pot metal casting.  The casting carries separate parabolic reflectors for the stop/tail and turn signal lights, but has molded-in reflectors for the backup and side marker lights.   All of the lamp sockets are removable from the backside (accessible from the boot) without removing the assembly or the lenses.

Sockets for the Stop/tail, the turn signal, and the backup lamps are similar, except that the stop/tail holds a standard 1157 dual filament lamp, while the others hold 1156 lamps.  The marker light has a simple bayonet socket for a common 1895 lamp.  

Though rubber boots try to protect the sockets from moisture, they sometimes fall short.  A few of my sockets had significant rust, which of course means that the protective zinc coating was long gone.

I believe these sockets are available through some of the usual suppliers, but in keeping with the overall spirit of this project, I preferred to try to save the ones I had.  To protect the steel parts of the sockets from future corrosion, some sort of durable coating would have to be applied.  I typically zinc plate small steel parts to protect them, but in this case there are copper parts in the socket.  I didn't think I could realistically take the socket apart or selectively plate the steel, so I landed on copper plating, which seems appropriate for an electrical device.  So, after removing all the rust, they got a coat of copper.  I only had to do this for the sockets on one side of the car.

Now, one of the prime directives on the overall TR6 project is to improve the electrical system wherever possible.  In many cases, this means improving grounding.  I'd wager that a sizable portion of TR6 electrical problems are caused by bad grounds.  It was a common practice in this era to use the body of the car as a return path for many of the electrical circuits.  While this works passably well when the car is new, there are approximately one bazillion places on this car where electrical return paths depend on intimate metal contact in joints that are also susceptible to corrosion.  

Take these tail light sockets for example.  In the return path, there is a copper finger that presses against the base of the bulb.  That finger is pinched by the plated steel ring that mounts the socket.  Spring fingers on the steel ring press against another steel plate that is mounted to the main tail light casting.  From there, there is a copper rivet that holds the plate to the main tail light casting, and also a male spade connector.  This connector gets a real copper wire that grounds the main casting.  With all the unsoldered dissimilar metal joints in the path, just add a few condensation cycles, and we start to have a compromised ground return.

I've seen some very innovative approaches to mitigating this situation, including soldering the copper finger to the steel ring in the socket.  While this is ingeneous and a good step in the right directrion, what I really wanted was an explicit ground terminal right on the socket.

What really got me thinking, though was when I realized that these sockets were designed to have a ground terminal.  There are four positions around the socket for connection terminals.  Only one is used for the 1156 sockets, and two for the 1157 sockets.  The ground finger that contacts the bulb base is mounted in one of the other positions, but doesn't have a terminal.

Here's how I remedied the situation.  I cut a little copper strap about 1/2" long and just narrow enough to fit in a groove above the ground contact.  This got soldered to the ground contact.

Then I modified some of these little "piggyback" spade terminals into a terminal that had a face that would neatly slide down into the socket just like the other terminals.

Then soldered the terminal to the copper strap.

In another little serendipidous moment, I discovered that the rubber boots already had provision for the extra terminal.

All three upgraded (well, I claim it's an upgrade) sockets for one side of the car:

The side marker socket was different--it's for a smaller 1896 lamp, but also did not have a ground terminal.  Luckily, I was able to find a two-wire socket that would fit the hole perfectly.

Being pretty happy with how those sockets turned out, I moved on to other little issues with the tail lights.

Here is the steel plate that the spring fingers of the socket mate with.  Even though it's not in the electrical ground path any more, I wanted to take care of the rust.

That plate holds the aluminum turn signal reflector, and the two are attached to the casting by two rivets.

I would normally try to re-plate the steel part, but I wasn't sure I could separate the plate fromt he reflector without maiming the delicate reflector, so I left them together , removed the rust, and powder coated the plate and the backside of the reflector.

Then there was the stop/tail reflector.  It is plastic with a mirror finish--I guess either chrome plated or vacuum deposited aluminum.  Either way, the reflective coating was very thin, to the point of being able to see through it in places.  It wasn't nearly as reflective the one on the other side of the car.

I thought a lot about this, looked at a lot of silver, even "chrome" paints, but none of them were very mirror-like.  I ended up learning a new technique and applied aluminum leaf to the reflector.  Aluminum leaf is analogous to gold leaf (but, you know, cheaper).  It is like aluminum foil but much thinner--only about half a micron (about 20 millionths of an inch).  The result is still not a mirror, but better than any paint I saw.

One other thing had to be sorted out on the tail lights.  Some of the mounting studs were seized and twisted off during removal.  The studs have a short square shank under their small heads, and are pressed into the soft pot metal casting.  It didn't take much to pop them out.  I was able to find some small carriage bolts that match the 10-32 threads of the originals, but with a bigger head.  The dimension of the square was very close.  Most places, the carraige bolts worked fine, but I had to reduce the diameter of the head in a few places.  Also, the new bolts are stainless, so corrosion souldn't be a problem.

Then it was on to the lenses.  I was able to clean up and polish all the lenses except the broken one, which I replaced.  The only other thing regarding the lenses is that some of them have built in reflectors.  The reflectors are just thin aluminum, like a heavy foil.  Most of them had come loose and had to be flattened and re-glued.  The reflector in the stop/tail lens is behind a glued-on cap that has to be popped off.

There was also a tricky repair of one of the fastening bosses on one of the side marker lenses.

Since I was reusing most of the old lenses, I had a small concern about stripping the fastening threads in the soft plastic.  The best way to reduce the risk is to re-use the original screws so there won't be any additional thread cutting.  The original screws were pretty rusty, but cleaned up OK.

As with most things that come in pairs, I did one side first.  The second side is always much faster.

Now, on to the lamps themselves.  In addition to improving the grounding system on the car, I wanted to experiment with reducing the electrical load.  By doing this, I might be able to accommodate new loads like seat heaters without having to upgrade the alternator.  One way to reduce load is to change out incandescent bulbs for LED units, which produce light much more efficiently.  There is a dizzying selection of LED replacements for the ubiquitous 1156, 1157, and 1895 incandescent lamps.  I bought a few, more or less at random, though I did try to select those with higher lumen output.  One other quirk about LEDs that is different from incandescents is that they come in multiple colors, and the colors are not achieved by filters.  The colors are a result of the actual materials that make up the LED.  So for LEDs it doesn't make sense to buy a white LED and then put it behind a red filter which would block all but the red light.  A red LED on the other hand emits light predominately in the red part of the spectrum, so a red filter won't block much of it.  LEDs made to replace automotive incandescents come in red, amber, and a couple of shades of white.

One concern is whether the LEDs would look as bright as the incandescents.  Here are some clips of side-by-side tests.  In each test, the incsandescent lamps are on the left, the LEDs on the right.

Tail lights:            

Stop lights:         

Turn Signal lights:

Backup lights:   

Side marker lights: 

As for the electrical load savings, here is the current drawn from one side with all the lights on.  The current reads a little over five amps, but note that the voltage has dropped from 14 to 10 volts.  That's because the power supply has a max output of five amps, and it folds back the voltage as necessary to not exceed that.  The calculated current at the full 14 volts would be north of seven amps.

And here is the situation with all LED lamps on.  The current is just over one amp (look quick--the camera scrambles to screw down its aperture to adjust to the sudden bright lights).

So it appears that the LED lamps will reduce the maximum electrical load from the back end of the car by around 12 amps.  Maybe I can actually use my seat heaters!

Front Side Marker Lights

The front side marker lights are pretty simple--a metal frame that carries the lamp socket, a rubber boot that doubles as a gasket, and a lens.

The good news is that the marker socket has a ground terminal.  The bad news is that it uses one of those cheesy fake bullet connectors where the wire just wraps around a little metal sleeve.  That will be easy to fix.

There was some corrosion on the metal frame, and it was a little distorted so I separated the socket from the frame, straightened it up, and replated it.

Reassembled the socket with a real soldered bullet, and pushed in new carraige bolt studs like for the tail lights.

I continue to be amazed by the durability of some of the old British rubber parts.  Cleaned up, the rubber boots look better than some new rubber parts I've bought.

The US markers had an internal reflector, and "chrome" on the perimeter of the lens, both apparently not included on the European models.  My reflectors were detached and roaming free inside the lens, so I had to glue them back in place.

The chrome on lens surround was in pretty bad shape, so I scraped it all off.  I didn't waste much time looking for paint, but fell back to my newfound technique of metal leaf that I used on the tail light reflector.

I'll be proud to put these back on the car someday.

Front Signal Lights

The front signal lights are also pretty simple.  A cast frame holds an aluminum reflector and lamp socket.  A rubber boot covers the backside and seals against a lens at the front.

Ther was a little sheet metal work to do on one of the reflectors.  There was no body damage in this area, so I wonder if it was installed this way.

Unlike most of the other lights on the car, the mounting studs here didn't break off on disassembly.  They were pretty rusty, though, so they just got derusted and replated.

Happily, the these fixtures also have a real ground wire connector.

Took the sockets apart for cleaning.

The rubber boots were in wonderful shape.  The only defect was a small tear--looked more like a cut, acutally--in the side of one of them.  I fixed it easily with a patch from a bycycle tube repair kit.

Ready to go...


Well, I made a valiant attempt to save my headlight buckets, but when all the paint and rust were removed, there were just too many holes that shouldn't be there.  Considering the cost of new ones, I just ordered a pair.

These buckets come without the proper spring clip to hold the chrome finish ring.  The little fastener piece has to be removed and the correct clip riveted on in its place.

Then the headlight adjusting screws have to be installed with their little plastic grommets.

The inner rims which cradle the sealed beam unit from the back side showed quite a bit of corrosion.  It's more than just cosmetic.  Rust indicates that the zinc plating is breached, and the deterioration will only get worse.  These pieces are a little large for my small plating tank, so I powder coated them in a matte silver.

The inner rim attaches to the adjusting screws, and is held in place by a spring hooked at the bottom of the bucket.

The wiring harnesses to the sockets were a mess.  There were splices in the buckets, and the insulation on the wires was chafed in a few places.  I considered trying to find the wire terminals that fit inside the connector housing and just make new pigtails, ut in the end, I just ordered new headlight pigtails.

The new pigtails were mostly OK.  They appeared to use good quality terminals well crimped.  I added some heatshrink for a little extra protection.  

One small disappointment was the grommet that fits in the bucket.  The original grommet appeared to be molded on the wires while the replacement was just a rubber sleeve that was a loose fit over the wires.  If the grommet was intended to seal the bucket or provide strain relief, the new grommet was going to fail.

I removed the grommet from one of my original pigtails and since it was still in very good condition, I slid it onto the new pigtail's wires (after removing the soldered bullet termoinals).  My other original grommet was missing, so I had to appeal to a generous members of one of the popular TR6 forums.  I had one on a few days.

While I had the pigtail apart, I decided to replace the rather cheesy looking sleeving with some heavier stuff I had on hand.

A little more heatshring to  seal things up, and the pigtails were installed.

I'll be considering an LED conversion for these headlights, so this is as far as I'll go, but these are pretty much ready to install.

All this lighting work has been a background task for the last month or two.  It was finicky, but enjoyable.  There wasn't much cost except for the LED lamps.

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