Wiring Fan Override in SPF

[MidOHasp]

I am looking for the procedure to install a fan override switch in my SPF 1670. Every now and then, the needle is going over 100 and it always happens when I'm running hard and then get stuck in traffic or something. My thoughts are that I'm getting some heat built up, but while I'm at speed, it has no problem keeping up. Then, when I stop, the fans just aren't kicking in early enough to keep the temp down.

Sitting at an idle in the driveway, over the course of 10-15 minutes, the water will get right to 90 and the fans will cycle on and off normally. After hard driving, the temp will start climbing slowly as I'm standing still, but the fans won't always kick right on at 90. Maybe 94 or 98. My thought is that the water is getting hot in the motor and as it passes over the sending unit in the intake manifold, it's showing me that it's getting hot. But by the time water gets to the radiator (takes longer in my car than in most due to some creative custom plumbing), it's been a while, and the water that is NOW getting to the sending unit is REALLY hot. By the time the fans kick on, there's water in the system that is much hotter than it should be, and even with the fans, it has a hard time cooling off a slow rolling boil.

My thinking is that if I hide an override switch, and I'm running hard, I can flip it on as I slow down or get stuck in a parade. It will keep the water about where it should be.

So 2 things...

1) Is my logic somewhat sound? Does my explanation sound like a reasonable one for why I'm having the problem?
2) How do I wire the override on a newer SPF? I want to keep the thermostatic control on them, as well. Seems like a fair number of you have done this.

Thanks, in advance, as always, for all your help.

PS - for those of you following my overheating woes of last summer/fall, this is not that. Thank God. This is nice gradual minor overheating. A welcome change from where I was almost a year ago.

PPS - running a 160 stat, will be switching to 180. Since all of my woes happen after 160, my thoughts are that 180 being the so-called "right choice" will not exacerbate my problem.

[Randy Rosenberg]

You might want to try the Superformance Cobra Owners Forum ;-)

[GT35065]

I have the same engine as you (408 stroker) and about same HP #'s (500). I have the exact same problem with heating up under the same conditions as you. Especially where I live in FL, it not only gets hot this time of year, we have lots of stop and go traffic.

I installed a fan override switch myself. It is easy to do and you can get the schematic faxed to you from Mark at Dynamic. It is about a 1/2 hour job. I leave my fans on all the time in traffic and it keeps it between 90-100. When cruising, I leave the switch off.
Only problem is with my fans on my blinkers don't work due to draw on alternator. I need an alternator that puts out a little more juice, especially at idle.

Good luck,
Rick

[RedBarchetta]

Confused....Don't you have a manual switch on the dash? My #747 (3-4 years older than yours) has one from the factory. I figured this was standard on ALL SPFs. I flip it on during long lights. In fact, on a recent circuit to the beach and back, I ended up using it so much that I broke the switch! Finish Line sold me a replacement for $20, and I was even able to knock out the wrist pin and repair the original.

-Deano

[Mr.Fixit]

The normal swith for SPF's is a thermo switch located in the side tank of the radiator, driver's side. Two spades stick out of it, when hot the switch becomes continuitous. I believe (memory isn't getting any better) that it just completes the ground circuit for the fan relay trigger. So to turn the fan on with the radiator not hot, pull the wires off the thermo switch and connect them together, or you should be able to just connect (the correct) one to ground. You might be able to get a different temperatre rated thermoswitch too, but they are a pain to replace with an odd size and fiberglass in the way.

[MidOHasp]

Randy,

I've never been on SCOF. I have my hands full here.

GT - I will call Mark. Maybe I can catch him when he's in between hits of amphetamines. Good guy, most polite person I know....busier than heck, though!

Red - Nope, no switch. I have a fuel pump switch, Defogger switch, and headlight switch.

Mr. Fixit - So what you're saying is if I install a switch that is a second connection between the two wires running of the spades on the thermoswitch, I have my fan override.

If the hot water closes the circuit, fans. If my thumb closes it, fans. If both are open, no fans, if both are closed, fans.

Right?

Thanks, guys.

[Mr.Fixit]

Yes, run a switch that jumpers the two wires going to the thermoswitch.

In fact, I believe that you only need to have a switch that connects one of those two wires to ground.

You should be able to do it all behind the dash, without running wires all the way to the left front corner of the car.

[Mike Simard]

While you're doing fan wiring, it wouldn't hurt to make sure they both rotate the right way. I just happened to notice that one of mine was backwards, I have no idea how it got that way.

[MidOHasp]

Mike...I was a lucky one, my fans are going in the right direction.

Mr. Fixit - I think I will take GT's advice and get ahold of a schematic of the under-dash wiring.

Thanks for the help guys...

JP