I'm in process of installing electric fans to a completely rebuilt engine pushing around 430-450HP. I'm using the painless performance wiring harness 30117. I don't know where to get the "ignition 12v" from. I believe it has to be a line that is hot when the car is in "run" and "acc" but not "start"? if that is true, where the hell is that?!?!?

 

Hi, I am sooo the right guy to answer this. Put electric fans on my 77 in about 06 give or take.
bought Flexalite fans from Ecklers. By the way, Flexalite have been great.
Painless harness. ..... well that many breakdowns later. Let me tell you to pitch this in the garbage RIGHT NOW!!!. save yourself the breakdowns!
to run your fans. You need a thermo switch or a fan controller or run them off your EFI.
I am happy to help you, first, how are you switching the fan or fans? Thermo switch? Or ECU.
second, one or twin fans?
Pull power for the fans at the solenoid, positive battery cable connection. Top large post.
there are only 4 wires to a relay. One to ground which is the thermo switch. One to switched power. This is a very light load so acc. Power at fuse panel is a good spot. One to the fans and of course main power taken off the solenoid.
All the wiring in the painless kit is undersized.
The circuit breaker is a BAD idea. Replaced 3 of them.
I can get far more specific if I know more .
Use a fuse down at the solenoid connection. I'm running a 60 amp fuse and 60 amp relay with twin fans.
Scrap the painless kit right now!
get back to me with what your running and I think I can save you the pain I went through with the "painless " fan harness.

 

I don’t know a thing about the brand of harness you have although it sounds like someone else had a bad experience with it.

For the main 12v power for my elec fan as well as “switched” power I pulled both from the always hot main lug on the alternator. If I happen to shut down when the fan is spinning it will continue to cool until the thermoswitch is satisfied regardless of ignition switch position.

I feel like it can’t hurt for the spal fan to be blowing air all over the engine components as things cool down. The most it’s ever run in this situation is about 5 minutes. Obviously you need a healthy battery/charging system for this to reliably work.

One time I shut the engine down when it was right on the cusp of getting hot enough to turn the fan on. It came on about 1 minute after I had switched off as heat soak made the thermoswitch go to ground. She ran a couple minutes and switched off.

Of course the thermoswitch might fail someday when you’re away from your car and your fan would run continuously until your battery was dead. On my C3 I have a simple knife blade switch on the negative battery terminal that I use anytime I’m away from the car for any meaningful length of time.

This setup is not for everyone but it works for me.

 

Depending on how many things you plan on hanging off of your fuse box, you might consider a remote fuse box. I have fans, stereo, dakota digital gauges, fuel pump, and Sniper EFI, so I opted for the remote to keep from hanging everything off of the singe acc and bat plugs in the fuse box.

 

Agree with remote fuse box and a relay set up. I got mine from Ron Francis. Heavy gauge wire That can handle any fan set up. Check them out.

 

See below- one way to wire-

You can get your ignition source off the fusebox-

As far as acc & ignition-

The acc wire is hot in ACC and ignition -but not start ( yellow- used for wipers and radio)
The ignition wire is not hot ACC but hot ign and start (pink- gauges/turn signals

You don't want to wire the fans to the alternator- it can't handle the start up surge for the fan(s)- especially since usually the car is at idle and the alternator is NOT able to produce full power-most (dependent on pulley size) are full output 1500-1800 RPM.
Wire as close to battery as possible- Starter lug works great- as the battery will stabilize the voltage and have more current available when needed.
Think of the alternator as income and the battery as your bank account...at idle the alternator is only earning part time money!!!

Another issue that might arise- if you have a stock alternator- you might run into problems keeping up with the power demands- and ending up with a dead battery.

You might want to look at something like this- a PWM- Pulse Width Modulation controller for your fan(s)
1) Uses a soft start- doesn't pull full current immediately when the fan(s) start up
2) Has it's own temp sensor - and uses temperature to control the speed of the fan(s)- so only runs them full speed when needed
3) Has built in relay to control the high current switching
4) Has an over ride switch to turn on the fan if ever needed
5)No need to run an ignition wire-

PWM-
https://www.summitracing.com/parts/der-16796

 

Where exactly on the fuse box do I get the ignition source? do i need to run a wire into the cab of the car? Or is there a way to hook in from the engine harness.

 

ouch. Thanks for the heads up!

 

Where exactly on the fuse box do I get the ignition source? do i need to run a wire into the cab of the car? Or is there a way to hook in from the engine harness.

 

ouch. Thanks for the heads up!

 

The yellow wire at the wiper motor will be hot in ACC and RUN but not hot in START. The ACC terminal on the fuse block would work or ACC terminal on the ignition switch.

The sensor they provide that is on at 185* and off at 175* is too low a temperature for a 180* thermostat. It will basically keep the fans on all the time unless you're running a 160* thermostat.

From looking at the picture, I'm tending to believe the wiring is too small a gauge for dual fans too.

 

should I get a 195 or something thermostat for the waterneck?

 

I used ACC. on the fusebox for switched power.Power directly from starter.I also used a BMW dual temp sensor 185/195, dual fans from a 2001 Corvette 2 relays 2 fuses.

 

Thermo switch,
twin fans

 

O.K. first, make certain that you have enough Alternator to run this. I would suggest 100 amp alternator minimum.
second, the only thing in that painless kit that is usable, is the thermo switch. As someone else pointed out. Will pretty much have your fans running all the time once you've reached warm up.
this isn't the worst thing. But if your cooling system is set up properly, you really shouldn't need to be running them on the hiway.
if you haven't ordered this kit yet, don't. Look on Summit for just the thermo switch. They are available in different temp settings
with twin fans, you can wire with 2 fuses and 2 30 amp relays. Or one larger fuse and a large heavy duty 60 amp relay.
for Alternator , electric fans, headlight relays, etc. I would suggest you look up "Mad Electrical ". There web page is full of information as well as they can help you with parts.

 

I already have the kit, but I am starting to regret it....

 

When I bought my twin fan setup years ago. I really didn't understand the load/ Current draw of twin fans. I too just bought a "Painless Electrics ". Wiring kit.
have had 3 circuit breakers fail. Circuit breakers just don't work with underhood temps and fan startup surges. Use a fuse. The relay they supply is not enough for twin fans. Melted the connections twice and changed 4 relays. Melted wiring connections at the fans.
the painless kit is just not up to twin fans.
you need a proper fuse, not a breaker. You need heavier wire. And you definitely need a properly setup charging system.
if you haven't gone to Mad Electrical's web site and read there tech pages on Alternators yet. Please do so.

 

I’m not understanding why some folks say not to pull main power for the fan or fans from the main lug on the alternator. That lug connects directly to the starter. Which connects directly to the battery. Pulling 12v from the alternator lug is essentially the same as pulling from the positive lug on the battery.

My 75 has been configured this way for 2 1/2 years and 5000 miles with zero issues. As pointed out by others any fan activity is nearly always at idle. My fan kicks on strong whenever necessary regardless of engine rpm.

Granted my car does have a modern alternator and otherwise healthy electrical system.

 

The wire off the alternator was NEVER designed to handle that kind of current- You do realize if the alternator doesn't supply the power for the fans- the current will be pulled from the battery.

The wire runs from the starter THROUGH a fusible link- which could easily be burned by pulling too much current- its a 10GA wire that's already maxed out by the factory electrical- GM cut corners here...

I just don't recommend it...

 

ahhh Richard454 that makes sense thanks for that. I didn’t realize any running C3 still has that fusible link thing. My car has an upgraded heavy gauge wire between the alt and starter.