Temporary/improvised e-fan wiring? | Ford Explorer Forums - Serious Explorations

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Temporary/improvised e-fan wiring?

Lars xls

February 21, 2011
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City, State
Year, Model & Trim Level
2001 XLS
Hey all,
I just finished installing a 2sp T-bird fan in my 4.0, and have ordered a DCC controller based on the info I've found about them on this site. However, the controller has not arrived on schedule, and I have a trip planned for the weekend. I would prefer to improvise a temporary switch solution, rather than trying to undo a weekend's worth of fan installation in the rain to put the mechanical fan back in. So here is where i need help.

What is the cheapest, easiest solution to wire up the fan and make it run (safely)? It must last a week and about 1000mi.

Also, I have a digital temp sensor, so manual fan control can be done accurately.

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Best option would be to have the ran run the entire time. I recently sold my Mitsubishi Eclipse that had a problem where the ECU wasn't telling the fan to turn on (though the temperature sensor was saying, "HOLY BALLS - IT"S BOILING!!!").

Run 12ga wire to / from the fan, and get a simple switch going to the cabin. I'm certain there's a grommet you can thread the wires through somewhere. It's cheap. It's dirty. But it works.

Best of all, you can Ctrl+Alt+Del it when you're done. Perhaps use the wire, and switch for another project?

This sounds like a good solution, but do I not need some sort of relay? And how do I control the amount of power that gets to it? Tap into some accessory line, and add a fuse for good measure?

One thought that came to me after posting, was redirecting the wires from the fog lights to the fan. Im seeing this as a potential solution, because: (a) there is an in cabin switch already, (b) it incorporates a relay and (c) has the fuses and wiring already in place. It should have enough power, as I believe the fog bulbs are rated at 37.5 Watt.
The downsides I see would be: (a) lights must always be on, (b) no fan when my brights are on and (c)no fog lights for the week. Can anyone see any reason why this wouldn't work, or what kind of other problems this might cause?

Again, thanks for the help and input, electrical systems are not my strong point.

I'm just trying to be logical... I had a super basic setup in the Eclipse. Literally ran 12ga wire from the battery terminal, to the switch, to the fan.

I'm going to assume your fan is a generic 12V, 20A setup? If I'm not mistaken, you should be able to just dummy wire it (no relay necessary). The only reason you'd need a relay is if you wanted to use small (i.e. speaker) wire (18ga) to run to your switch.

EDIT: Also, I don't think the wires going to your fog lights can carry enough current to power your fan (safely). If there's anything close to the wires (i.e. - them leaning on the chassis), you have a VERY high chance of shorting something, if not everything out. (Okay, everything is an overstatement, but with electronics, you never know).

My concern about using the relay was that the amperage of the fan may overpower the amperage rating of the switch and burn it out. My local shop carries up to 30 amp switches last time I checked and the The T-bird fan can draw a lot of power. I did find some info on the Taurus and Mark VIII amperage draws (The T-bird fan is about half way between the 2). http://www.thehollisterroadcompany.com/TaurusMarkVIIIrelay.html cites the taurus fan peaking at 32 amps on low, and the Mark viii peaking at 40 amps at startup. Splitting the difference, i would guess that the t-bird would draw about 36. My guess is that a 30 amp switch would manage this for a week? Any thoughts?

Also, I had a major brain-fart and processed Watts as Amps when referring to the fog light specs. Wire gauges are probably very thin, now that i think about it, and Kyle you are probably correct about short-outs occurring there.


My guess is that a 30amp switch will be enough for a week long trip... Admittedly, I was using a ten amp, with a twenty amp draw... not very smart, but it worked without a glitch, so I bet yours'll be fine too. Another thing to note is where you're getting your switch from - O'Reilly / Autozone / Kragen only had up to the 30 amp switches which I thought was a lot, but probably enough for a number of different circuits on a car... However, I was browsing through Radio Shack the other day (for ***** and giggles, of course), pondering light / power / car-puter projects, and ran across 50 amp switches... maybe have a look around there? They were like 5 bucks... cake, if you ask me.

After some quick Googling, I came up with this. Should be kosher. Switch

How many amps does that fan pull? My guess is a 20 amp or so draw continous if not more with a higher spike..

I would not run a fused hot wire to a switch and then directly to the fan. To keep the voltage drop down you would need extra large wire and that switch won't last and will be a fire hazard.

If you need to manuall run it via a switch just use a relay.. it very little more wiring and will keep things safe.

If your worried about forgetting to turn it on, just grab one of those inexpensive Hayden fan controlllers with the "probe" to control the fan for now.

Assuming your fan is in back of the radiator (I'm assuming that since your replacing the factory fan) and there is enough uncovered area of the radiator you could get away with it running as long as the truck is running.
You just need to make sure that air can get through the radiator and out past the fan without going "through" the fan. Otherwise you may run hot on the freeway since the spinning fan will actually slow down the air going through the radiator when the fan is running while going down the freeway. Some fans have "flaps" on the back to keep this problem from happening, or just leave about 1/3 of the radiator uncovered (flaps is a better choice).


Very simple to temp your fan wiring. Use 10 gauge from relay to fan and fan to ground. Use 14 gauge from switch to relay and relay to ground. You don't have to run the ground wires back to the battery, you can run them to a good ground screw in the engine bay. Since the switch doesn't carry the load of the fan any switch will do. Just make sure you get a 40 amp relay. Quick sketch to get you going.


Thanks Kyle-wait... I mean thanks guy whose name I don't know...

While you are out buying a relay, buy two. They are inexpensive, and come in handy. Just a little information for you....there are several relays in the engine fuse box that could go bad at any time. I have had a few fail and had to move them around to get the fuel pump working. An extra relay in the tool box would have come in handy.

So I got my fan all wired up! I went straight from the battery, through a 30amp switch and 30 amp fuse via 10ga wire. My local shop had a terrible selection of switches and relays in stock. But, 400 miles later, it seems to be working perfectly *knock on wood*. I can tell it would not be a great long term solution, as the fuse gets pretty warm during the fan's startup, but has not blown yet (once I got the ground situated properly). I'll keep you all posted on how well it lasts.

And thanks for the wiring diagram! Didnt get to use it this time around, but I can definitely think of some future projects that will need it.

No problem, glad you got it worked out.

Yes. I had to skip the relay. Wouldve liked to use one though.