Manual Fan control

I've decided I need to install a manual fan control for my pass. fan. It NEVER runs, except when the terminals are wired directly to the batt. In city traffic and any outside temp. over 50 or so my stock guage is scary to watch.

I've read about using the prem fuel switch as a source but don't understand how to do that or what it would accomplish.

I was planning to install a lighted switch in the slot where the power antenna switch goes since I don't have that option.

Should I wire the switch to a relay or can I just wire it straight off the switch? The fan's only a few amps, right?

Ideas? Suggestions?

Personally, if I were going to do it, I would use a relay. I would wire the positive terminal of the fan directly to the battery, and the negative terminal would go through the relay. The relay coil would be wired so that the positive end is connected to switched power, and the ground is through the manual fan switch. That way, the fan would be getting its juice directly from the battery, but only when the manual fan switch and ignition switch are both turned on. That way, wiring is not overloaded, and you can still avoid worrying about the battery dying because the fan was left on.

There is probably a better way, but I don't have the later EVTM to try to find other circuits to patch.

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Mike Walsted - NATO member
1986 5-speed TurboCoupe .

Mike vis right.... use a relay (30 A fog light relays work great).

Personally, I prefer to wire things the "opposite" the way mike describes it, although both Mikes way and my way will work just fine. My way: 10 ga wire from batt to relay contact. 30A fuse in this wire as close to the batt as you can get it. Other relay contact to fan pos. terminal with 10 ga wire again. Switched power source under dash to switch, switch to relay coil, other relay coil terminal to ground.

The EEC runs the activators at 12 V all the time, and grounds them to turn them on, like Mikes way of doing the wiring. The EEC does this because it introduces less electrical noise into the EEC when the EEC switches an activator on or off. In the case af a fan switch and relay, noise is not a factor, so it can be wired either way.

You might also look into getting a aux thermostat to turn the fan on and off at any preset temp. Most parts stores have then for about $20. On my TC, I left the EEC fan control intact, so the fan still turns on with the A/C, or if my own control system fails. I have both a dash switch to turn the fan on manually (in the power ant switch location), and a aux thermostat to turn it on automatically at about 185 deg coolant temp. The aux thermostat and manual switch are just wired in parallel.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)

[This message has been edited by Jeff K (edited 03-29-2002).]

If the picture uploaded this is what mine looks like.

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NATO Member
88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS. Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges.140 mph Motorsports Speedo New engine: Total Seal rings and TRW pistons, ported and polished head w/ cc'd chambers,1.59"exhausts, SS valves, gutted upper, knife edged lower, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, and rod bolts. Walbro 255 HP pump and Kirban adj FPR, T-3. Centerforce II, KB subs and jack rails.

Thanks guys. Jeff, I followed your directions with my headlights and foglights too and they're working perfectly.

Another mini-project and hopefully I can keep this thing running. [Image: smile.gif]

I have been having trouble with mine again too. I guess smacking the black box only works so many times [Image: smile.gif]

Anyway , why not use the existing wires and splice in a new relay there??? That way the computer would still turn it on and its fool proof.

OR why not repin the black box (just like a computer) to use the secondary relay as a main relay?

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GT350R
#1978 20th 2.3 Turbo T-top
#3608 20th 2.3 Turbo T-top
WAY too many TC's and other mustangs!

My Garage

Got my external relay for the fan installed. I put a blue rocker switch in place of my unused power antenna slot. It looks and works great. The switch almost looks like it belongs there [Image: smile.gif] Maybe I'll get a pic scanned one of these days. Supposed to be in the 80's next week so I'll get a chance to see if the temp will stay down. Thanks again Jeff K.