• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR2/3/3A TR3B horn wiring

Share this page

T

TFB

Jedi Knight
Country flag
Offline
Old wires feeding horns appear to be two 12 g,one for each horn,on their own fuse and 12g gound wires inside horn from old harness.
The new stering column harness horn ground looks like a 16g that willl carry the ground for both horns.
I would like to avoid a relay,but may go that way.
Am I missing something? Why such small ground for both horns?
Where does horn ground get back to chassiss?through the column brace?
Also if i do use a relay,do I need one 10g for fused power and would it make more sense if relay is used to ground horns at base and send + from relay?
Also what is american fuse size for the horns,I believe A1.
Thanks
Tom
 
The harness through the steering column has to be small enough to pass through the space. I didn't try to measure, but I suspect you'll find that the conductor is bigger than it looks (and the insulation thinner). In any case, that is how it was wired originally.

I'm not sure which path the current follows, whether through the brace or through the steering box, but I would guess the latter. There are felt and nylon bushings between the steering wheel/shaft and the outer column.

Not sure I follow your relay comments. 12 AWG should be plenty, but using 10 certainly won't hurt anything. And the relay can be wired on either side of the horns. Mine is on the ground side, to minimize wiring changes.

Later cars used a Lucas 35 amp for the horns, so AGC 20 would be a suitable substitute.
 
Thanks Randall,
The 10g power question was because I see originally each horn had it's own 12g,and I would be feeding both with one 12g if I run one power to the relay so I thought maybe a 10g.
Was it horn contact damage or stator tube harness wiring that lead you to install the relay?
BTW thanks also for your suggestion in a previous post about 5-8 amp od fusing to protect the od solenoid if it hangs up.Im running an all new harness so I put a 5 inline,and will increase if needed.

Thanks again
Tom
 
TFB said:
Was it horn contact damage or stator tube harness wiring that lead you to install the relay?
Click to expand...
At the time, I thought it was contact damage; but I later discovered that the 4-way sleeve was broken internally and not making good contact with the bullets. This is where the wire originally from the control head meets with the wire to each horn.

Now I think I may just have a flaky horn, but I haven't gone back in to troubleshoot.
 
Back
Top