Triumph Sprint St 955i 2005 Headlights

Hi Gary

 

No wiring changes required - just insert the relays in the vacant slots
These should be located under the instrument panel on your 955 ST
(p.s. it's a 2004 even if reg'd in 05 - 05 models are 1050)

p.s. If the relays are already there (and sounds like they are if there are indeed 4 relays in that location) then check Fuse # 1

 

That would be unusual coincidence for both relays to be bad.
You specifically checked Fuse #1?
Did you check the bulbs?

 

No, they are both H4 Dual Filament bulbs - it is not possible to install anything different.
It is certainly possible that the high beam filament is blown in one and the low beam filament in the other.
Honestly, most likely issue is Fuse 1

 

this ^

 

If you can reach the connectors, swap them between the two lights
a) if you get same lights exhibiting which works only on low and the other on high, then you have bulbs issue
b) if the working beam on each light is now transposed to the opposite light (follows the connector) then you have a problem with the supply (most likely on the relay side of the circuit)
That will at least give you a conclusive answer as to what to pursue.

As an fyi, this is how the lighting circuit works:
One lamp gets power to low beam directly from the hi/low switch and to the high beam via the high beam relay;
the other lamp gets power to the high beam directly from the hi/low switch and to the low beam via the low beam relay.
The same signal from the hi/lo switch that powers each lamp directly is also used to energize the relay coil;
supply power for the tow relays comes from Fuse #1.

Another quick test you can do:
Of the 4 relays
1 x 3-pin relay - this is the turn signal module
1 x 5 pin relay - this is the headlight-cut relay
2 are 4-pin relays - these are the high and low relays and the ones you want
Turn on Key-Switch to enable the headlights
Pull each of the relays and replace it again
When on low beam on switch you should be able to hear/feel the low beam relay click when you pull/replace it
(if the first of the two does not click, try the other one and ensure that at least one of them clicks in the low position of the switch; repeat then for the other relay with high beam selected)

if NEITHER clicks, then you probably have a relay problem (or a missing ground on the relay sockets)
If BOTH successfully click, then the possibilities are
a) Fuse 1
b) the bulbs themselves

 

Good job
Unusual circumstance where both relays would be bad - although who knows how long first one was bad before second one failed
They are 15 years old I guess

 

It is quite common on the ST and RS 955i that both relays fail in quick succession, there are uprated relays available, lots of suppliers stock them, I had to replace 2 lots when I had an RS, the single light on main and dip was due to complying with European compliance, seems crazy when you are more visible with both lights on, also better for night riding, some people have uprated the bulbs, however it appears this upgrade put the relay under more load, and subsequent premature relay failure.