As to my above post:
Quote
The wiring diagram for 1948-49 in the shop manual reprint shows the connections you have are correct however there should be one more. The wire from the battery terminal of the solonoid should go to the same terminal as the horn wire (the + terminal).
This wiring configuration is correct if the truck is still wired per factory specs. Gord brought up a good point though. If this ammetter is an add-on replacing the one in the dash, the in-dash one must be taken out of the circuit.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.