quick question about what size relay i should run. i currently have a black magic electric fan on my car but i am going to replace it with a 3.8 taurus fan i just picked up. the black magic fan is kinda hacked up from whoever owned it before me and it is currently wired through a 30 amp relay to a switch in the car. i want to leave it wired to the switch, my question is what size relay do i need. i did a search and saw where someone recommended a 75 amp bosch relay. i just want to make sure my car is wired correct. i checked the volts with the fan off/on, off my volts were 14.4 and when i turned the fan on they went to 13.8 for a second and then right back up to 14.3. also what guage wire should i be using i know what is on there is way too small. thanks for the help!
electric fan relay
- Thread starter 306lx
- Start date
ram360
Founding Member
I was using a 30a w/ mine when I had it in the car...I think the wire was 12g but not totally sure might have been smaller.
. Here's a table:
18 gauge wire = 5-8 amps
16 gauge wire = 10-12 amps
14 gauge wire = 15-17 amps
12 gauge wire = 20-25 amps
10 gauge wire = 30-40 amps
8 gauge wire = 50-60 amps.
Keep in mind that the wire size in the chart is for the circuit itself, not the size of the fuse link or fuse. The packages of fuse link repair material you can get at the auto parts stores also will have a current rating on them.
18 gauge wire = 5-8 amps
16 gauge wire = 10-12 amps
14 gauge wire = 15-17 amps
12 gauge wire = 20-25 amps
10 gauge wire = 30-40 amps
8 gauge wire = 50-60 amps.
Keep in mind that the wire size in the chart is for the circuit itself, not the size of the fuse link or fuse. The packages of fuse link repair material you can get at the auto parts stores also will have a current rating on them.
Absolutely run a fuse on the power wire. Here is my take: install as many fuses as you want. If no issues ever arise, none of them will ever blow. But should something pop up, you want all those fuses there and hope they blow.
IIRC, Ford Muscle's write up (Taurus fan in a fox) uses SPDT 30 amp relays. However, you dont want (IMHO) the relay to flow close to its capacity.
Simply said, you can probably use the 30 amper, but I would use a 75 if you can.
A DcController would be the way to do it and forget it.
To measure the amperage draw from the fan's low and high speed, you would need an inductive meter which can show amperage draw.
Good luck.
IIRC, Ford Muscle's write up (Taurus fan in a fox) uses SPDT 30 amp relays. However, you dont want (IMHO) the relay to flow close to its capacity.
Simply said, you can probably use the 30 amper, but I would use a 75 if you can.
A DcController would be the way to do it and forget it.
To measure the amperage draw from the fan's low and high speed, you would need an inductive meter which can show amperage draw.
Good luck.
thanks for all the replies. when it comes to electrical i like to ask as many questions as i can. i will try to figure how many amps the fan draws and go with the correct relay. what exactly does a relay do. if i knew that would probably help me determine exactly what i need. also why run a fuseable link instead of a fuse? thanks again for all the info guys!!
Michael Yount
Mustang Master
Mike piqued my interest with that one as well. I would actually run a circuit breaker myself (unless he has a reason not to).306lx said:
A relay is like a big switch. It allows you to eliminate having all the power going into the cockpit, through 20' of wiring, and back to the fan. You locate the relay (normally) close to the fan and battery. The battery power goes into the relay and waits to be sent to the fan. THe battery power into the relay is the common terminal. The terminal out of the relay to the fan is the N.O. terminal (these two connect when the relay is energized).
To activate the relay, it requies having the coil be energized. This is done by the coil seeing power and ground at each respective terminal on the relay. These are low amperage handling wires (control wires).
Good luck.
http://www.fordmuscle.com/archives/2003/02/electricfan/index.php
so i dont have to explain it.this kit has worked for my setup for the last
10 yrs and still spinning...
and many others in here have used this posting great results..
so i dont have to explain it.this kit has worked for my setup for the last
10 yrs and still spinning...
and many others in here have used this posting great results..
I just wired in a 3.8 Taurus fan, am VERY happy with the
results.
A control that's similar to the DC Controller but I believe
a little less $ is the (new?) Flex-A-Lite soft start, variable speed controller.
After some research, I found that a Taurus fan pulls about
33 amps on high. There's a popular magazine article about installing one that has some incorrect info - it's actually a reprint of an earlier article installing a Mark8
fan which draws more, with some of the wording changed.
Anyway - after inquiring with FAL cuz the info in the Summit online catalogue was a little unclear, I found I needed the larger of the FAL controllers - just under $100 on Summit. Will handle 40 amps continuous. No relays needed with it.
You can see a good instructional on it at the Flex A Lite site, check out Automotive, Electric Fans, Accessories, and it will go to an Install article.
It soft starts to avoid the amp draw spike, is variable speed so the fan runs at varying speeds depending on how much warmer the motor gets than the ON setting you set.
You hook it to the high speed side of the fan motor.
You can add switches to completely shut it off, or to run it in spite of the motor temp. I added an LED in my dash to show when it's running, per that article above. When you start a warm engine, it delays starting the fan for 5
seconds to avoid a double draw while the starter is turning the motor, and will run the fan after you shut the motor off to cool the coolant in the radiator down to your "ON" setting.
FAL customer service was VERY good to work with, too.
results.
A control that's similar to the DC Controller but I believe
a little less $ is the (new?) Flex-A-Lite soft start, variable speed controller.
After some research, I found that a Taurus fan pulls about
33 amps on high. There's a popular magazine article about installing one that has some incorrect info - it's actually a reprint of an earlier article installing a Mark8
fan which draws more, with some of the wording changed.
Anyway - after inquiring with FAL cuz the info in the Summit online catalogue was a little unclear, I found I needed the larger of the FAL controllers - just under $100 on Summit. Will handle 40 amps continuous. No relays needed with it.
You can see a good instructional on it at the Flex A Lite site, check out Automotive, Electric Fans, Accessories, and it will go to an Install article.
It soft starts to avoid the amp draw spike, is variable speed so the fan runs at varying speeds depending on how much warmer the motor gets than the ON setting you set.
You hook it to the high speed side of the fan motor.
You can add switches to completely shut it off, or to run it in spite of the motor temp. I added an LED in my dash to show when it's running, per that article above. When you start a warm engine, it delays starting the fan for 5
seconds to avoid a double draw while the starter is turning the motor, and will run the fan after you shut the motor off to cool the coolant in the radiator down to your "ON" setting.
FAL customer service was VERY good to work with, too.
Michael Yount
Mustang Master
Be careful there macx -- they've had reliability problems with their variable speed controllers -- quality isn't nearly as good as dcc.....
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