How to wire aftermarket AC condenser fans to come on when the AC is turned on?
05-04-2014, 09:24 AM
#21
Normally you would determine wire gauge based on current draw and length as you have mentioned. However, since you don't know the draw of the fans, it's helpful to remember that fuses protect the wiring not the attached device. The fuse is there to blow before the current flow becomes enough to overheat the wire and possibly cause a fire. So, if you use a 30-amp fuse, you need to use wire that can handle at least 30 amps over its length for at least several minutes (fuses don't blow immediately when the current is only a little above their rating). That way you know the fuse will blow before the wire overheats.
There are many charts on the internet that show what gauge wire to use with 12VDC for current capacity over a given length. They vary widely because some take into account other factors such as allowable voltage drop, type of insulation and whether the wire is bundled in a harness or "free air".
The short answer to your question is that 14 gauge is fine for a short run (less than 8 feet) to handle 30 amps for something like fans because voltage drop is not a big issue. For an amplifier or other voltage sensitive piece of equipment, 10 gauge would be required for the same 30 amps over a short run to maintain less than 3% voltage drop.
There are many charts on the internet that show what gauge wire to use with 12VDC for current capacity over a given length. They vary widely because some take into account other factors such as allowable voltage drop, type of insulation and whether the wire is bundled in a harness or "free air".
The short answer to your question is that 14 gauge is fine for a short run (less than 8 feet) to handle 30 amps for something like fans because voltage drop is not a big issue. For an amplifier or other voltage sensitive piece of equipment, 10 gauge would be required for the same 30 amps over a short run to maintain less than 3% voltage drop.
05-04-2014, 09:24 AM
#22
for the oem setup, it's a 10 amp fuse in the under hood fuse box for the radiator fans.
based on that i doubt your new fans will draw more than that especially if they are smaller in size. I would not use a 30 amp fuse, that is too large. i would go with a 10 amp fuse to start, if you blow it then up it to 12 or 15 amp, assuming you're using a fuse holder like in my diagram. changing a fuse is simple and that's it's purpose, don't defeat that purpose by using a 30 amp fuse.
14 gauge is the norm generally and would be more than sufficient for a planned 10-15 amp draw. you could use 16 gauge if you wanted going for the load side of the relay which powers the fans, based on an amperage draw of 10 amps (which i doubt it's that much) you're only running about 5 feet. i would get some primary wire from the auto store, a spool each of red and black it's inexpensive. for the switching side of the relay, i think u were planning on tapping off the AC clutch wire as a switch, the current draw on the switching side of your relay is nothing so for that you can use 20 or 22 gauge wire. if you have no wire i would just buy a red & black 30' spool of 16 gauge and do everything with that, using 14 gauge to wire the switching side of relay would be overkill but it's up to you what wire you prefer and spend money on, using larger wire won't hurt anything other than your pocket and it can be harder to work with.
also check the relay you are using and verify the coil in it on the switching side is 60 ohm or higher, or it states something to the affect nominal current draw 133 milliamp. the draw should be less than 200 mA or 0.2 A.
example:
14 gauge black 20' $7:
http://shop.advanceautoparts.com/p/a...m=primary+wire
16 gauge red 30' $7:
http://shop.advanceautoparts.com/p/a...m=primary+wire
based on that i doubt your new fans will draw more than that especially if they are smaller in size. I would not use a 30 amp fuse, that is too large. i would go with a 10 amp fuse to start, if you blow it then up it to 12 or 15 amp, assuming you're using a fuse holder like in my diagram. changing a fuse is simple and that's it's purpose, don't defeat that purpose by using a 30 amp fuse.
14 gauge is the norm generally and would be more than sufficient for a planned 10-15 amp draw. you could use 16 gauge if you wanted going for the load side of the relay which powers the fans, based on an amperage draw of 10 amps (which i doubt it's that much) you're only running about 5 feet. i would get some primary wire from the auto store, a spool each of red and black it's inexpensive. for the switching side of the relay, i think u were planning on tapping off the AC clutch wire as a switch, the current draw on the switching side of your relay is nothing so for that you can use 20 or 22 gauge wire. if you have no wire i would just buy a red & black 30' spool of 16 gauge and do everything with that, using 14 gauge to wire the switching side of relay would be overkill but it's up to you what wire you prefer and spend money on, using larger wire won't hurt anything other than your pocket and it can be harder to work with.
also check the relay you are using and verify the coil in it on the switching side is 60 ohm or higher, or it states something to the affect nominal current draw 133 milliamp. the draw should be less than 200 mA or 0.2 A.
example:
14 gauge black 20' $7:
http://shop.advanceautoparts.com/p/a...m=primary+wire
16 gauge red 30' $7:
http://shop.advanceautoparts.com/p/a...m=primary+wire
05-04-2014, 01:31 PM
#23
There is a formula to figure out appropriate wire guage for the amount of amps and the length it needs to run, but I don't know what it is. I just go by what seems sensible.
Cooling fans draw pretty good power, especially on startup. Your fuse box is located fairly close underhood, I would guess that 12g wire would be adequate for the switched-side wiring. On the control side of the relay, 16g is all you need.
Cooling fans draw pretty good power, especially on startup. Your fuse box is located fairly close underhood, I would guess that 12g wire would be adequate for the switched-side wiring. On the control side of the relay, 16g is all you need.
