Aux Fan Amp Draw

[UNL1MTD]

I finally wired up my aux fan on a manual swith (been sitting around for about a year). My 87 4.0 manual without AC did not have one from the factory, so this was a little extra insurance with the radiator being as old as it is. I used a typical wiring scheme; I put a switch in the dash that gets power from the battery, which powers a relay, which powers the fan. My question is, what amp fuse is appropriate for the fan? I figured that a 10amp would be a safe bet, but it popped it easy as soon as the switch flipped. I didnt have anything else on hand to test with, so I figured I would ask before buying some more fuses tomorrow.

 

Thanks,

 

Sean

[HOrnbrod]

I finally wired up my aux fan on a manual swith (been sitting around for about a year). My 87 4.0 manual without AC did not have one from the factory, so this was a little extra insurance with the radiator being as old as it is. I used a typical wiring scheme; I put a switch in the dash that gets power from the battery, which powers a relay, which powers the fan. My question is, what amp fuse is appropriate for the fan? I figured that a 10amp would be a safe bet, but it popped it easy as soon as the switch flipped. I didnt have anything else on hand to test with, so I figured I would ask before buying some more fuses tomorrow. Thanks,

Sean

 

If it's the OEM aux fan, they can pull about 15A on startup. I use a 20A fuse on both of mine on the load side of the relays, and have not blown one yet. :thumbsup:

[UNL1MTD]

good to know, I will get some 20 amp fuses for the load side of the relay and give it another shot. Thanks for the fast response :thumbsup:

[lostissues]

what fan do you have? 8 blade? 10 blade? (cannot remember the others maybe a 6 blade?)

I put a 10 blade fan in my 87 which is the best of the factory fans and according to the 99 fsm I have it required a 40 amp fuse.

[HOrnbrod]

what fan do you have? 8 blade? 10 blade? (cannot remember the others maybe a 6 blade?)

I put a 10 blade fan in my 87 which is the best of the factory fans and according to the 99 fsm I have it required a 40 amp fuse.

 

I have two 1997+ 10-blade fans mounted. I load tested these fans and they pull about 16A/ea on startup and run at about 9A-10A/ea. Since I saw your post I went down and checked my fuses as it's been awhile. Both are running on 25A fuses (not 20A as I posted before UNL1MTD, so p/u 25A fuses if you have the 10-blade fan) with no problems. Also am using standard 30A relays for both w. 10AWG wiring on the load side of the relays. This is heavier wiring than stock. The smaller the fuse you can get by with the better protection you will have. :cheers:

[UNL1MTD]

well, I opted to get 2 of each 15, 20, and 25 amp fuses. And as luck would have it it runs just fine with the 15 amp fuse. So I'll be keeping that. I do have the weaker if not the weakest factory fan though, just the 6 blade fan. It does move a good bit of air, but boy is that thing loud. I definitely won't forget if I left it on. I bought it used, so I'm wondering if thats just how they are or if there is a bearing on its way out.

[HOrnbrod]

It does move a good bit of air, but boy is that thing loud. I definitely won't forget if I left it on. I bought it used, so I'm wondering if thats just how they are or if there is a bearing on its way out.

 

The old style square blade fans are the noisest, move the least CFM of air, and draw the lowest AMP rating because the motor is smaller. The new 97+ 10 curved blade fans pull more air, but also draw more amps on startup. They are all interchangeable except for the connector. But if the square blade fan works for you and keeps everything cool, UB okay. :yes: