Ken K
I'm Awesome
Their are two types of cooling fan motors. Those with traditional series wound fields are larger in size and can pull 20-30 amps. The "Flat" type motors use a round magnet (Toroidal) use 10 -15 amps. Newer fan blades with an "S" shape are very quite and move from 200 to 500 cfm either in push or pull applications. I do not know what alternator you have, but a GM Trucks in the late 90's come with CS133D as later C/K have AD244. They change be interchange to upgrade to the AD244, one of the toughest on the market. The website "Alternatorman" has a voltage regulator D200SEL that converts a junk yard find to a one wire alternator. To increase the life of the AD244, look at his D897SE kit, that uses 80 amp diodes, copper diode plate, brushes and previous regulator. Outputs of 250 amps or higher can be achieved with the AD244 if needed, but heat kills the diodes and engines both. Find a simple screw-in one wire temp switch, get it as close to the engine side of the thermostat and use it to ground a fused relay to control each fan, with common switch. To be on the cheep, you can install a toggle switch to control one or both on those days you need it. Note: Many digital amp clamps are sold for under $30 that are extremely accurate as compared to my Fluke toys and will give you the current used over all, or in each circuit. If you have a lot of electrical toys other than stock, check each circuit to ensure the correct fuse is selected for harness protection. Fuse pop due to the heat generated from over amperage from it's rating. Time v Amps for fuse operation as cold copper coils may pull 22 amps when first turned on, but operate continuously at 15 amps heated up while running.