Electrical fan wiring for the mentally impaired

[Clumzi]

I removed my mechanical fan and replaced it with a 16" electric fan mounted to my radiator. In the past I've wired e fans on an old motorcycle and in a Toyota Van but both of those were wired to toggle switches and directly to the battery.

I'd like to wire this fan a bit more classy. I want it wired to a thermal switch.

I've searched all over the intertubes and for whatever reason I can not wrap my brain around how to do this in my '91 2.3.

If you were to hold your 8 year old's hand through doing this to your truck... yea. Not the sharpest tool in the shed. Do I buy a new switch? Use an existing temp sensor? Where should I splice the power into the existing wiring?

Is there something in the tech articles I've missed? Existing tutorial?

 

[RonD]

There are several type of thermal switches available, easiest would probably be one that uses a probe that inserts into Radiator fins, so no holes.

Google: radiator thermal switch

These usually come with a relay.

A relay doesn't use amps, the Load wires on the relay do.

Battery-----fuse for fan-----------thermal relay----------e-fan-------Ground

Key on power------- thermal relay(not e-fan power)-----Ground

So thermal relay can only close when key is on and when thermal probe gets warm enough, the on temp is adjustable.


Thermal setups often have A/C triggers as well, so turn on the e-fan when A/C is on, which is a nice addition if you have A/C

 

[Clumzi]

So a probe style switch is what I'm looking for, correct? Something like this guy?

http://www.summitracing.com/parts/hda-3653/overview/

No a/c in the truck.

So I'm running a wire from the battery to an inline fuse (what size fuse?) to the relay to the fan to ground and then a second wire from key on power (where is a good place to tap into? Just with a butt connector?) to the relay to ground?

What seems odd about that to me (if I'm understanding) is running two sets of wires to the relay. It looks like it has two spade connection points (like in and out) as opposed to four - which you'd need to run a circuit from the battery and then another circuit from key on power. Unless I'm just running a wire from key on power and splicing it in w/ the wire from the battery to the relay.

 

[RonD]

Look at the fan motor to see what size fuse you need, if motor is 7amps then use a 10 amp fuse, if motor is 10amps then use a 15amp fuse.
And make sure the wire you use can handle that amp rating.

The point of a fuse is to pass enough amperage(power) to a device so it can operate but if a failure/short should occur the fuse will separate/burn out cutting power to device, preventing wire insulation or device from catching on fire.

Yes, that is a Rad probe temp sensor, but that is all that is included, it is not a "kit" to do a fresh install.
The two spade connectors would be used to activate a separate relay that would provide power from battery/fuse to e-fan.

So if you got that probe you would also need to get a 12volt SPST relay rated with at least the same amp rating as the fuse you will get.

So:
battery-------fuse-------12volt relay(load)-------e-fan------ground

Fused 12v key on---------rad probe------12volt relay(on/off)-------ground

When key is on rad probe gets 12v to pass to 12volt relay when temp is high enough.
That 12v closes 12volt relay which then passes the battery/fuse power to e-fan.


Relays come in different types
The voltage rating is for what is needed to close/activate the relay(on/off), so a 12volt relay needs 12v and a ground to close/activate.
This is a simple wire coiled around a metal bar, when power is passing thru the coil of wire the metal bar becomes a magnet, this magnet then pulls down a spring loaded "contact" that connects the "load" terminals, when 12v is removed the spring push "contacts apart and "load" terminals are disconnected.
The relay part doesn't use many amps, less than 1 amp, so can be added to existing fused circuit without blowing the fuse.

Simplest relay is an SPST, single pole, single throw
It will have 4 terminals
2 for the coil, the relay part, 12v and ground, there is no + or - as long as one is grounded and the other gets 12v it will work.

The other 2 terminals are for the "load", this would have an amp rating, so a 12v 40amp relay would mean it is activated(on/off) by 12v/ground and could safely pass up to 40amps between the "load" terminals.
The load terminals also have no + or -, in your case you would connect battery/fuse wire to one "load" terminal and the e-fan to the other "load" terminal.
When key is on the rad probe gets 12v, when rad gets hot enough rad probe passes 12v to 12v relay, relay closes and battery/fuse power passes to e-fan.

This would be an example of a rad probe kit with relay included:
http://www.summitracing.com/int/parts/der-16759/overview/


EDIT:
Found this site with pictures of relay and e-fan
http://www.autospeed.com/cms/article.html?&A=112716

 

[Sasquatch_Ryda]

http://www.therangerstation.com/tech_library/volvo_electric_fan.shtml

http://www.therangerstation.com/Magazine/Summer2003/ElectricFanInstall.htm

 

[Clumzi]

Alright. The weather is starting to warm up, so I need to tackle this soon. Now I feel like I can kind of wrap my head around it and these are the kind of resources I couldn't find searching myself previously. Thank you. I'll dig this thread up once I start wiring the fan.