I am putting in an electric fan and wondered about a relay. I was just going to wire it to run with a toggle switch that was keyed power. wondering about a relay and did I need one? have to have one, what the heck is it for ? I know nuthin'
Need help with electric fan wiring
- Thread starter hankthebigdog
- Start date
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RPM
The Rat Master!
I would suggest you pick up a good 30-40 amp relay from the auto parts store. There should be a wiring diagram on the box.
Dr Crankenstein
Rocket Surgeon
A relay is basically a heavy switch designed to carry big loads/amps. You can still use a toggle switch, but it will only signal the relay to open or close.
This way, your switch doesn't have to be wired with fat gauge "hot" leads, and it won't melt down from the heavy load. You can wire the switch to provide the relay with ground as its signal if you want. Then, you have NO hot wires at the switch.
Like RPM says, pick one up and read the instructions/diagram. It's easy.
This way, your switch doesn't have to be wired with fat gauge "hot" leads, and it won't melt down from the heavy load. You can wire the switch to provide the relay with ground as its signal if you want. Then, you have NO hot wires at the switch.
Like RPM says, pick one up and read the instructions/diagram. It's easy.
sgtpontiac
Older, Wiser and Still Buildin'
They've got some really inexpensive fan wiring..
that uses a temp probe attached near the return tank of the rad.....they are cheap, less than $30....are adjustable to a degree and easily wired up...comes with a 30amp relay and everything you need.....Just a suggestion..
that uses a temp probe attached near the return tank of the rad.....they are cheap, less than $30....are adjustable to a degree and easily wired up...comes with a 30amp relay and everything you need.....Just a suggestion..
darkk
Well-known member
I'm running a twincooler double 12" fan on my Hudson coupe. I just wired them direct to a heavy toggle switch. I turn it on after starting the car and shut it off when I'm done. 2 years without any problems yet.
thanks fellows for all of the education..sometimes I just go brain dead and others I just dont have a clue. You guys and gals are great help. again thanks.
bob w
Still crazy after all these years!
I also just use a heavy duty (50 amp) toggle switch and heavy gauge wire. Less components to buy and fail. But, I'm old and set in my ways.
Toad
Well-known member
Use a relay, there's a reason they make them. Fans draw a lot of juice and I doubt any electric fan manufacturer would recommend otherwise!
Toad
Toad
goose-em
Well-known member
I use a fan relay that I bought from Autocrap for about 30 bucks. It is the universal one with the temp probe.
I eliminated the temp probe and wired a toggle into the wires for the temp probe, now I can turn it on and off at will.
I could also put the temp probe back on if desired and the relay is adjustable for temp.
Relay ensures you have twelve volts at your fan.
Cost of fan, $100 plus dollars, cost of relay, $30 dollars, seems to be a no brainer.
I eliminated the temp probe and wired a toggle into the wires for the temp probe, now I can turn it on and off at will.
I could also put the temp probe back on if desired and the relay is adjustable for temp.
Relay ensures you have twelve volts at your fan.
Cost of fan, $100 plus dollars, cost of relay, $30 dollars, seems to be a no brainer.
bob w
Still crazy after all these years!
A relay is an electrically actuated switch. A toggle switch is a physically actuated switch. As long as each is rated for the load it will see there is no difference in terms of safety, longevity, etc.
If you want the fan to be thermostatically controlled a relay is necessary. If you don't have a thermostatically controlled fan, but use a relay, then in effect you have two switches; the relay for high load and the toggle for the low load control circuit.
In my applications I hardly ever turn the fan on, just when sitting in rush hour type traffic so I am content to flip a toggle switch when needed.
The Spal fan I put on my Plymouth truck has 12 gauge leads coming from the motor. The wiring kit I used has 12 gauge wires for an electric fan already so I just hooked it up.
I'm not anti-relay. In fact I have used them at times. Just saying there's more than one way to safely wire a fan.
If you want the fan to be thermostatically controlled a relay is necessary. If you don't have a thermostatically controlled fan, but use a relay, then in effect you have two switches; the relay for high load and the toggle for the low load control circuit.
In my applications I hardly ever turn the fan on, just when sitting in rush hour type traffic so I am content to flip a toggle switch when needed.
The Spal fan I put on my Plymouth truck has 12 gauge leads coming from the motor. The wiring kit I used has 12 gauge wires for an electric fan already so I just hooked it up.
I'm not anti-relay. In fact I have used them at times. Just saying there's more than one way to safely wire a fan.
Last edited:
donsrods
Well-known member
We have had no luck with any of the electric fan controllers that turn the fan on and off automatically, even the SPAL one didn't work right out of the box. (And we LOVE SPAL fans) So I just run a relay to take the heavy load and a manual switch in the dash and I keep an eye on my temp gauge. When it needs more cooling I pull out the switch and when it goe down I push it back in. My 27 has been that way for 23 years and has never had an issue.
I posted this recently and it might be worth reposting. I was having an issue with my electric fuel pump continuing to run for a few seconds after the key was shut off. Come to find out the spinning electric fan was backfeeding current until it stopped and was acting as a generator, feeding juice to the lights and electric pump. If I shut the fan switch off first the pump and lights die as soon as I turn the key.
Don
I posted this recently and it might be worth reposting. I was having an issue with my electric fuel pump continuing to run for a few seconds after the key was shut off. Come to find out the spinning electric fan was backfeeding current until it stopped and was acting as a generator, feeding juice to the lights and electric pump. If I shut the fan switch off first the pump and lights die as soon as I turn the key.
Don
sgtpontiac
Older, Wiser and Still Buildin'
Manually turned on fans are ok....
if you keep an eye on things....most of us probably would...but if somebody is concerned that they might forget....I'd still go with a relay and temp sender unit....either engine mounted or the probe type....I've personally never had a problem with even the cheapest ones (like from autozone)....but if you want to wire it quick for manual, use the relay and just use a switch to ground the relay ....or put in both...the sender/probe and combine it with a manual in case the probe fails......
if you keep an eye on things....most of us probably would...but if somebody is concerned that they might forget....I'd still go with a relay and temp sender unit....either engine mounted or the probe type....I've personally never had a problem with even the cheapest ones (like from autozone)....but if you want to wire it quick for manual, use the relay and just use a switch to ground the relay ....or put in both...the sender/probe and combine it with a manual in case the probe fails......
sweetnomad
Well-known member
Make sure you still run a switch even if you use a temp sensor,so in the event if the sensor ever fails you can make the ground though a switch on the inside of the car. In other words it will by-pass the sensor and create a ground to turn the fans on. Might save you some grief if your down the road without a paddle. Sorry sgt.pontiac duplicated what you said!!!!!! Skipped through the posts and missed it !!!!
LOWANDRATY
Well-known member
fan
This is the one i'm running, no problems with it at all so far, keeps the temp around 190, if you don't have loud exhaust, then you will here this fan coming from a mile away, but it moves a lot of air. It comes with the relay, wire harness temp. sensor, and circuit breaker, very simple hook up. ebay item 380385768132
This is the one i'm running, no problems with it at all so far, keeps the temp around 190, if you don't have loud exhaust, then you will here this fan coming from a mile away, but it moves a lot of air. It comes with the relay, wire harness temp. sensor, and circuit breaker, very simple hook up. ebay item 380385768132
junker39
Well-known member
I used a two speed Volvo fan that blows a lot of air and is fairly quiet. It runs on Low speed normally. I put a 190* idiot light sensor, on the intake, below the thermostat. Using a two contact relay, the fan runs on Low until the sensor trips the relay into High speed. When it cools off below 190*, it goes back to Low. Hey, it works in the driveway. Not road tested yet.
Rev Tex Devlle
He's workin' 4 da Lord, in a '46 Ford!
here a diagram for ya!
http://www.facebook.com/photo.php?fbid=376141124235&set=a.376137864235.154557.544479235&type=3
http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash2/24880_376141114235_544479235_3449937_7113249_n.jpg
http://a4.sphotos.ak.fbcdn.net/hphotos-ak-snc3/24880_376141134235_544479235_3449940_5963028_n.jpg
http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc3/24880_376141139235_544479235_3449941_2671450_n.jpg
hope it helps
http://www.facebook.com/photo.php?fbid=376141124235&set=a.376137864235.154557.544479235&type=3
http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash2/24880_376141114235_544479235_3449937_7113249_n.jpg
http://a4.sphotos.ak.fbcdn.net/hphotos-ak-snc3/24880_376141134235_544479235_3449940_5963028_n.jpg
http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc3/24880_376141139235_544479235_3449941_2671450_n.jpg
hope it helps
thanks fellows. I went with a relay and switch in the dash. seems to work good. I run it most of the time, can turn it off/on if needed.
sgtpontiac
Older, Wiser and Still Buildin'
We aim to please.....
glad you got it sorted out.....
glad you got it sorted out.....
old man dave
Well-known member
- Joined
- Apr 5, 2009
- Messages
- 485
Has anyone here run an electric water pump on the street.They work great on my drag car with an electric fan. I would like to have a dash mounted switchable unit that powers a relay turning on the water pump and powering the thermal switch to turn on the fan as needed. Also couldn't you use a rheostat to control the speed of the fan since it is a DC motor.
sgtpontiac
Older, Wiser and Still Buildin'
No reason you couldn't run it on the street.....
dash mounted switch for the water pump is cool, used to ground the relay to turn it on....but the rheostat idea is not a good idea....the fan draws a ton of amps, the rheostat would cook......as it would have to be wired to the power feed to the fan motor and not the ground for the relay.....that relay would not work with a variable ground thru a rheostat....so I'd nix the rheostat idea and simply go with the termostatic switch to make the ground for the fan relay...JMHO
dash mounted switch for the water pump is cool, used to ground the relay to turn it on....but the rheostat idea is not a good idea....the fan draws a ton of amps, the rheostat would cook......as it would have to be wired to the power feed to the fan motor and not the ground for the relay.....that relay would not work with a variable ground thru a rheostat....so I'd nix the rheostat idea and simply go with the termostatic switch to make the ground for the fan relay...JMHO
