electric fan switch

Started by 57larry, March 28, 2012, 07:35:28 PM

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57larry

March 28, 2012, 07:35:28 PM
we have a debate going. I say you need a relay when wiring a toggle switch to an electric fan. other guy says that you need a good toggle switch only, no need for a relay. I say the toggle switch would burn out. your help please

oj

#1
March 28, 2012, 07:42:25 PM
I prefer a relay located near the fan.  That way you can operate the relay with a thermostat or override with the switch.  A large fan will take a lot of juice, a good switch can handle most fans but i'd prefer to feed the relay from the battery so there is little voltage drop, when you feed from a switch then the power comes from the battery to the fuse panel, from t the fuse panel to the switch then from the switch to the fan - lots of potential problems areas and voltage drop for something as critical as the fan.

WZ JUNK

#2
March 28, 2012, 08:41:52 PM
I always use a relay.  Most of the time I also use some type of sensor to turn the fan on.  The trigger part of the circuit is the ground side of the relay.  If it is wired that way, you can add a switch to ground the relay and then you are able to turn the fan on manually.  Personally, I do think you need the switch if you have the proper radiator, fan, and sensor.  The system should take care of itself.

John
WZ JUNK
Chopped 48 Chevy Truck
Former Crew chief #974 1953 Studebaker   
Past Bonneville record holder B/BGCC 249.9 MPH

UGLY OLDS

#3
March 28, 2012, 09:14:32 PM
The fan for my Model A uses a 70 Amp relay & I plan on using #10 wire to run it ....    Got any idea how big of a "toggle" switch I need to carry 50 or 60 amps on start-up???   ( There isn't enough room in the dash...)  :shock:

Like John says....If the system is designed & installed correctly , it will take care of it self ....Look at the relays on all the cars with OE electric fans ....Those systems work pretty good ....Even in the summer with the A/C on .... 8)


Bob .... :wink:
1940 Oldsmobile- The "Ugly Olds"
1931 Ford sedan- Retirement project

***** First Member of Team Smart*****

57larry

#4
March 28, 2012, 09:40:16 PM
I was thinking a 40 amp relay. I think my friend owes me lunch. thanks guys

wayne petty

#5
March 28, 2012, 11:49:36 PM
RELAY....  

plus PROPER sized wiring..  the relay shortens the path the electrons have to flow...

allows you to only need one to two amps of power to trigger the relay contacts closed..  so those can be 16 gauge wires..

the wiring for the electric fan should BE 10 gauge.. or larger. 8..  all depends on the amp draw of the fan...





Rrumbler

#6
March 28, 2012, 11:58:33 PM
With the relay, you can save a lot of money on wire; locate the relay in the shortest path from the battery or POS junction block and run the heavy wire, # 10 or #8 to run the fan for that short distance. Wire the relay operating circuit with lighter wire, #14 or #16 for example, and use a toggle switch that will handle the amps of the operating circuit.  Less cost for wire and switch, and you can locate the switch where you like.
Rrumbler - Older, grouchier, broken; but not completely dead, yet.

PeterR

#7
March 29, 2012, 06:40:02 AM
Quote from: "57larry"we have a debate going. I say you need a relay when wiring a toggle switch to an electric fan. other guy says that you need a good toggle switch only, no need for a relay. I say the toggle switch would burn out. your help please


Is it desirable to use a relay --yes.    Is it essential, --no.

Providing the wire is a suitable gauge and the switch is rated appropriately, the fan will work fine.   The installation is just a bit clumsy.    

A suitable switch is not as large as you might imagine.  The switch only needs contacts of a size similar to those in a relay, and  if you break open an old relay you will likely find the switching contacts are much smaller than you expect.

57larry

#8
March 29, 2012, 07:50:14 PM
thank you everybody for the great answers. my friend just wants to run a toggle switch. I don't know about that, I told him he should run a relay but I can't make him

parklane

#9
March 29, 2012, 09:39:15 PM
Can't afford to do it right, but can afford to do it twice. :roll:
If a blind person wears sunglasses, why doesn\'t a deaf person wear earmuffs??

phat46

#10
March 30, 2012, 08:52:28 AM
Quote from: parklaneCan't afford to do it right, but can afford to do it twice. :roll:[/quo

John, that was the business plan where I used to work, along with "we'll fix it when it comes back, we HAVE to ship it today"

57larry

#11
March 31, 2012, 07:23:08 PM
well, my buddy bought a 50 amp toggle switch to use. I told him to at least wire a fuse with it. he doesn't think he needs it

wayne petty

#12
March 31, 2012, 10:53:16 PM
a MAXI fuse...

or a

5 or 6" piece of fusible link...


either properly sized for the fan motor rating..

fusible links are sized 4 gage sizes smaller than the circuit they are protecting..

a 10 gauge circuit gets an 14 gauge fusible link

a 12 gauge circuit gets an 16 gauge fusible link..

a 14 gauge circuit gets an 18 gauge fusible link..

Glen

#13
April 01, 2012, 11:03:17 PM
while we are on the subject, i have been using this guys products....I really like the way it cleans everything up.

the footprint of this two relay board is the size of a business card.  I used one of them in my trunk to power my intercooler pump and my trans cooler fan.

you can see the built in fuse location, power in whether ground trigger or positive and the main power post in the center.

http://www.leashelectronics.com/images/2012-02-02_22-34-08_567.jpg

http://www.leashelectronics.com/images/2012-02-02_22-08-08_717.jpg

the pic is huge, so i edited it out of the post.
www.leashelectronics.com  Randy is the owner.
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