Adding electric fans to antique car

[GM Tech]

Wiring when a/c is on is okay- but use the a/c command from control head, not the compressor command- compressor can shut off for high pressure- and that is when you need the fan the most....Also be sure and use a relay in the circuit, you don't want to pull those big amps through a control head...I've seen fans wired to a/c relay,and when car is shut off, the compressor clutch stays engaged due to fan slowing down and acting as a generator- supply backfed voltage to the compressor coil. And the coil hisses on engine shut off.

[emsvitil]

You may need to upgrade your alternator.

A 71 is only like 60 amps.

[jeepsj]

Look at the fan controllers from DC Controls. They vary the fan speed based on need, and they can be commanded easily from the A/C circuit.

http://www.dccontrol.com/constant_tempe ... ollers.htm

[71403]

You don't say what you have for a radiator now but if it's a copper/brass change it out for an aluminium. Doesn't have to be fancy $$$ retrofit unit my experience running big block Olds motors in A-bodies was a single row AL from a late 80's GM FWD cooled better than any 60's/70's 3-row copper/brass.

Stock used OEM dual fan in series/parallel or single two speed fan is the way to go no need for aftermarket. Early 2000's Dodge 300M/Imperial fits well with minor work on a 27" GM rad.

A CS144 alternator can usually fit where a 10/12SI lived previously. 120 or 144 amps in a reliable OEM package. 96-2000 Chevy pickup with optional 140a alternator will get the correct mounting ears. V-belt pully from your alternator will swap on.

Somewhere I have a p/n for a 3/8" NPT GM fan switch with ~185dF turn on if you need it.