View Full Version : TR6 75 TR6 headlight issue

08-10-2012, 10:45 PM
Hi. Five days ago LH headlight is dim. Two days ago LH headlight is bright and fine and test drive. Today cleaned the three connection tabs on the light itself, yet LH headlight is dim again. Any ideas are appreciated.


08-10-2012, 11:41 PM
First thing I would check is where the black (ground) wire is attached to the body. Sorry I don't know offhand where that is on a TR6 but you can probably follow it backwards from the lamp.

If that doesn't help, try some detective work. For starters, does the problem affect both low and high beam? If so, it almost has to be the ground wire. If not, it's the wire (or connections) for that filament.

Take the bulb loose but leave the wires attached, then check the voltage right on the headlight pins. Now repeat the test probing the wire terminals (inside the plastic housing). If they are different, the plug is bad.

08-11-2012, 12:01 AM
Thanks Randall. It does indeed effect both the hi and low beam. Both are dim. There are three black wires related to the front light that are joined together under/within a rubber sleeve but I don't yet see where they are grounded to the body.

08-11-2012, 01:22 AM
The headlight ground is below and in the center of the grill opening. If you have the radiator shroud in place you will need to remove it to gain access. Once you locate the ground point, clean the terminals. Another thing to consider is to add a separate ground wire to each headlight. I have done this and never have had different light intensities ever again.

08-12-2012, 12:41 AM
My TR6 right headlamp had issues for several months. It was very intermittent, but seemed every time I drove at night, the right side would go off, usually for short periods of time, often involving bumps in the road. After cleaning all the connectors, and making sure the grounds were clean I was sure I had it corrected. When I tested the lights for state inspection, the right side didn't come on, and I was finally able to find the cause.

It was a bad bulb.

Just to possibly save yourself some work, swap the bulbs left to right and see what happens.

08-18-2012, 11:15 PM
Thanks Romanti and others for the tip. Removed the radiator shroud and located the spade ground connection. Cleaned the connector and the body tab thoroughly and LH headlight shines bright. Put the shroud back on, and guess what, LH dim. Remove shroud again and determine problem is where the bullet connectors for the ground for each light come together. Cleaned the bullet connectors but tough to clean the female connector encased in the rubber sleeve.
So used Remanti's solution and snipped off the LH bullet connector and grounded it directly to the body. So far so good.

Got me wondering - I'll eventually need replacement spade connectors and the rubber encased bullet connectors. What kind do you all recommend and from where.

Also, somewhat unrelated, what fuses do you recommend. I read somewhere that a 35 amp British fuse is not the same as a 35 amp US fuse. Anything to that?

Thanks all !!

08-19-2012, 12:42 AM
Also, somewhat unrelated, what fuses do you recommend. I read somewhere that a 35 amp British fuse is not the same as a 35 amp US fuse. Anything to that?

Absolutely !!! :yesnod:

The original Lucas fuses were rated by the current that will cause them to blow "instantly", while modern fuses are rated by the current that they will carry indefinitely. The difference is roughly two to one! So, if you want to use readily available fuses, an AGC 20 or SFE 20 is the nearest equivalent to a Lucas 35. However, they are slightly different in size; so there might be something to be said for buying reproduction Lucas fuses from the usual suspects. (Personally, I use a 20 amp circuit breaker instead.)

08-19-2012, 12:45 AM
From Randall, via Drew:

Like so many other things about our Triumphs, the British did things just a little bit different than the Americans, including what the ratings marked on fuses mean. The British Standard that Triumph used rated fuses by the current that was guaranteed to make them blow instantly while the American (and now international) standard rates fuses by the current that they will carry forever. Fuses work on heat, so a small overload may take a long time to build up enough heat to melt the fusible element and blow the fuse. How warm the fuse was to begin with plays a large role too. So the carry rating winds up being quite a bit lower than the blow rating... the difference is roughly 2 to 1!

So, what this means to you is that, if you elect to use common American standard fuses (Bussman is one maker, there are others) in your Triumph, you need to use a much lower rated fuse than what your Triumph documentation says to use. There have been cases reported where a restored Triumph has caught fire from a short, because someone used American fuses with the Triumph recommended rating marked on them... the short did not blow the fuse but instead set the wiring harness on fire!

Here is a conversion chart, lifted from a long-ago Bussman fuse catalog:

Bussman Conversion Chart

English Type American Standard Replacement
50 amp AGC 30
35 amp AGC 25
30 amp AGC 20
25 amp AGC 15
20 amp AGC 10
10 amp AGC 7 1/2
5 amp AGC 3
Personally, I feel even this chart results in fuses rather larger than needed, so for example I use an AGC 20 to replace the original "35 amp" fuse in my TR3A. My conversion chart would go more like :

Randall's Recommendations

English Type American Standard Replacement
50 amp AGC 25
35 amp AGC 20
30 amp AGC 15
25 amp AGC 15
20 amp AGC 10
10 amp AGC 5
5 amp AGC 3
Tim Buja and Glenn Merrell put on a good visual demonstration of the difference in fuse ratings at VTR this year, where they first put in a "25 amp" Lucas-equivalent fuse and applied enough load to blow it. Then they installed a "25 amp" American fuse and applied the same load. The fuse did not blow, but after just a minute or so the wire started visibly leaking smoke...

By the way, proper fuses with the correct British markings are available from the usual suspects (Moss, The Roadster Factory, Victoria British, etc.). The British Standard fuses are also a slightly different physical size than American standard fuses, so it's probably best to buy the proper British fuses. American fuses fit in most British fuse holders, but not all of them.

Randall Young
October 17, 2005

08-19-2012, 12:48 AM
Got me wondering - I'll eventually need replacement spade connectors and the rubber encased bullet connectors. What kind do you all recommend and from where.
The bullet sleeves I got from TRF appear to be good quality. The only problem I have with them is that the inner metal sleeve has a tendency to slide around inside the rubber, so it may need to be repositioned after inserting the bullets.

For spade connectors, my preference is to buy uninsulated crimp versions (Amp is best, but other brands will do), crimp them onto the wire, then solder the wire where it protrudes beyond the crimp. Then insulate with heat shrink tubing as appropriate. Last time I got them from MMC (https://www.mcmaster.com/#quick-connect-terminals/=iwuaqd)





08-19-2012, 06:10 AM
british wiring has the bullets and the sleeves too, they also sell wire by the foot in the correct colors, and they have complete wiring harnesses too,