Electric fan wiring help

[white90burb]

So im starting my dive into the wiring in my blazer. Basically im kinda stuck wrapping my head around the fan section. I know a lot has been covered but a lot of threads are missing and I'm trying to do a few unique things.

1st i will be using the windstar fan. Im trying to wire everything through the bussmann 10 relay/20 fuse holder. Main question is will a 35 amp relay be enough for each fan?

2nd. Planning on running the smaller fan off a temp switch, easy enough to do. However the larger fan i am wanting to come on when either the a/c is on or when im in 4x4. This is the part im having trouble trying to wrap my head around. I know the large fan has 3 wires allowing two separate triggers, and for a/c i will need a trinary switch. How ever trying to figure if ill need a separate relay for each trigger or not.

3rd. Will want to have a switch in the cab to have manual over ride for water crossings, and possibly an all on mode for emergencies. Not very switch savvy, but i believe a dtdp switch is what im looking for? Also with the switch im looking to switch with ground not power.

Any help or advice is welcome.

 

[AZ79K5Project]

For the AC - you have a couple of options - run the relay trigger from the compressor hot lead or AC dash switch. If you run it through any pressure switch or AC compressor wire, the fan will turn on and off with AC pressure. I’d prefer to have it on all the time but at the moment my large fan is turned on with the AC.

There are a lot of options with the Windstar fans. I did that swap and had some heat issues with the fuses, relays and relays. The two fans were only pulling a total of 35 amps, but the power on draw is high and the wires need to be able to handle repeated cycles. Windstar uses 40 or 50 amp fuses for each fan. I opted for larger physical relays and fuses. There’s a low speed resister that is used on the Windstar fan for a slow speed. I’ll see if i can their wiring diagram. I had it at one time. GM’s version of that resister (I’m not running a low speed - I was going to but decided not to: AC Delco 15-80458.

I went with two: Blue Sea Systems Maxi Fuse Block and in-Line Fuse Holder https://www.amazon.com/dp/B000THTBZO/ref=cm_sw_r_sms_c_api_i_Pl8ODbP6C265W

I also used two
Ehdis 12V 200A Relays Car Truck Motor Automotive Boat Car Starter Heavy Duty Split... https://www.amazon.com/dp/B01IV7CPDI/ref=cm_sw_r_sms_c_api_i_kn8ODbWA15V1G

Wiring a relay is easy. If you use a standard relay - may not be the best idea because of max loads - have the 87 and 87a terminals. Use a primary relay wired so that power is always allowed to flow until you energize it. You energize the relay (internal switch), the power is cut to the fans. My

I two temp switches on my intake that ground trigger the fans. The small one fires at 180 and the larger fan turns on at 190 or 200. I don’t remember at the moment.

So far so good. I still need to add the override switch to turn them off.

side note - I have a large output alternator with a smaller pulley so that I maintain charging current at really low RPM just off idle. If you decide to do the same - research the alternators’s max rpm and do the math. The pulley size I have will take the alternator within a few hundred RPM of its redline if my 350 ever gets close to the engine’s redline. I’m about a 2:1 alternator RPM to engine RPM.