Horn relay 1988-91

Hi there fellow bm drivers. My horn is on all the time
and i have checked the stering wheel buttons and they
are ok so i think it is the relay, i have a identicle
car for spares but i cannot find out which relay it is.
the weather is ruff so i don't want to stand outside
with me tester finding out if i can halp it so does any
one know which relay it is? Buy the way, does anyone
else think that the haynes manual for this car is the
worst manual in the history of manuals. I have found
countless issues that the book was of no use at all soch
as this one for instance. perhaps some one could
recomend another manual for this car, i only have 316
facelift with the m10 carb engine as my requirements are
rwd, durable car that is cheap to run and simple to fix.

               Cheers            Nick