fan in line switch

[MrBlimp]

Does any one have a schematic for the in-line fan switch?

I've read some people installing one to turn the radiator fan before the temp switch kicks in.

I am considering this modification.

I would also be interested in hearing any cons to this procedure.

[zachmac]

Does any one have a schematic for the in-line fan switch?

I've read some people installing one to turn the radiator fan before the temp switch kicks in.

I am considering this modification.

I would also be interested in hearing any cons to this procedure.

Page 7 of 10 (sheet 5) of the same Brad Artigue wiring diagrams I linked before.

It is a non-switched but fused power supply to one side of the fan from the fuse box (lt. blue wire) with the other side grounded or not based on the thermo switch in the bottom of the radiator. Any switch in parallel with the radiator fan switch that completes the path to ground will also make the fan run. 78 shouldn't have a relay (later cars do).

Advantage of a manual override switch is if you are stuck in traffic you can preemptively kick the fan on to get it cooling before it would kick on by itself. BUT, if your cooling system is working correctly you don't need it. I live in SC and my fan cycles on and off with the temp gauge varying over a 5 degree band using the bone stock wiring setup. The fan should also run on its own with the car shutdown after a long hard run as again it is not switched.

A disadvantage if forgetting to turn it off but that is hard to do as the make a lot of noise. For me the other disadvantage is it's extra wiring and again, if the cooling system is working, it's not needed (IMHO). I hate extra wiring but that's just me. That's why I've eliminated several yards of wiring from my 78 (mostly dual point, emissions, seat belt relays, etc. that I don't need). I also eliminated this exact mod that a PO had done.

Are you sure one of those extra "do nothing" switches in your center dash section isn't a fan override? Sounds like you PO liked messing with the wiring? If you do decide to do this just use one of those (assuming you have a unused two position switch) to run and extra ground to the fan ground side (in parallel with the radiator switch lead) and you'll have your override. This will require of course routing a new wire through the firewall, unless you can find an unused old emissions or relay wire on both sides of the firewall as it sounds like you have relay wiring probably in place but disconnected for the dual points and the EGR divertor?