Possibly, but it could also be the igntion switch or a wiring short.
Do you have a voltmeter or a 12v test light? If so, then:
1) Disconnect the large wire to the starter and make sure it is insulated (so you do not have unwanted arco-sparko action....!)
2) Reconnect your battery and test for 12v at the smaller lead to the starter; if 12V is not there, then the starter is faulty.
3) If 12v IS there, then remove the brown-yellow and brown wires from the starter relay and see if the 12v to the small starter lead goes away. If not, the relay is faulty.
4) If it does go away, then reconnect the yellow-brown and yellow leads to the starter relay, and test for 12v at the brown-yellow lead to the relay to make sure it is there. Then test to see if there is 12v or ground at the yellow lead to the relay. If 12V is there at the yellow lead, then it is the relay
5) If ground is at the yellow lead , then test the yellow wiring back through the firewall connector and to the ignition switch to see where the ground is coming from.
And, BTW, my schematic has errors (it shows the starter relay going to the horn button!), so I am just working through this partly from general knowldge.
