First try the adjusting screw on the back (depends on which model you have whether there are 1 or 2 adjusters.
Then you could take it apart and clean the points.
Have a look at post #253 in this thread to see a Series III horn in pieces Isuzu C240 powered Series 3
I don't think it would be commercially viable to repair the horn. If the windings are burnt out it's probably a throwaway anyway.
Colin
				
			 
			
		 
			
				
			
			
				'56 Series 1 with homemade welder
'65 Series IIa Dormobile
'70 SIIa GS
'76 SIII 88" (Isuzu C240)
'81 SIII FFR
'95 Defender Tanami
Motorcycles :-
Vincent Rapide, Panther M100, Norton BIG4, Electra & Navigator, Matchless G80C, Suzuki SV650
			
			
		 
	
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