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**A1971Blazer** · 01-08-2024, 09:36 AM

My '67 has two fans, I wired the PCM fan 1 wire, which simply grounds the relay, and the ground from the trinary switch together to the relay ground (85) for fan 1
85 and 86 can interchange since they only energize the coil that closes the main contacts,
so either the pcm or the trinary switch, (or both depending on engine tempº) will provide the ground when the fan is needed.

01-08-2024, 09:36 AM	#2
A1971Blazer Senior Member Join Date: Nov 2013 Location: East Tennessee Posts: 2,109	Re: 64-66 C10 vintage air with LS question My '67 has two fans, I wired the PCM fan 1 wire, which simply grounds the relay, and the ground from the trinary switch together to the relay ground (85) for fan 1 85 and 86 can interchange since they only energize the coil that closes the main contacts, so either the pcm or the trinary switch, (or both depending on engine tempº) will provide the ground when the fan is needed. __________________ 1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer ............. Last edited by A1971Blazer; 01-08-2024 at 09:46 AM.