How to wire the fan to a switch?

[Sp00ner]

Trying to wire the radiator fan to a switch can I can hit to make the fan come on, but retain normal functionality with the switch off. I noticed that while I was staging, I would get up to 220 before the fan would come on, finally figured out that turning on the AC would get the temps down quickly. Since it makes the fan come on right away. Is there a way I can tap that circuit, or install any other setup to get the fan running when I want, without running the AC? Is it as easy as running a wire from the battery, to the fan? I assume that a 12v signal would turn it on, then when I turn that switch off, it should go back to normal, no?

[WopOnTour]

Originally Posted by goofyguy

Im sure WOP will show you this as soon as he comes on. Remeber realys are 1 way so if you install one between the fan and the standard relay the stock one should go unaffected. I think I know how to do but to explain would be fun. He can just Print up the actual wiring of the car and show you where to wire in.

It wont be as easy as you might think, due to the complexities of the relay system wiring. This is necc only to allow a method to run BOTH cooling fans in series to provide low speed mode, and then be able to run them in paralel for high speed. (the IC pump is no biggie) Anything done with aux relays could just set DTCs as the PCM monitors the control circuits for logic faults. So if you for instance GROUND the circuit to turn on a fan or the IC pump with a seperate relay (when the PCM isnt commanding a ground) it will eventually set a DTC (Takes 2 "trips" with 30 seconds of FAIL) But as long as it was done with the IGN OFF it "might" be OK.
Will look at it on weekend
WopOnTour

<EDIT> Come to think of it , it might just be easier to just "piggyback " onto the cooling fan motor wiring (and IC pump motor) directly with a couple of big relays to a dash switch. Then the ECM could do whatever it wanted as it doesnt look at the motor circuits at all, just the relay "control" circuits.-WOT

[WopOnTour]

Well here's the schematics for the fans and the CAC pump motor
Like I said you will need to "relay" into the main motors circuits directly essentially bypassing ALL of the control side to prevent DTCs
Havnt had a chance to make up a "modified" schematic for you yet...
WopOnTour

[WopOnTour]

OK
Here's my first go at a switch control to run BOTH fans and the Charge Air Cooler (aftercooler) pump from a switch with the engine off. According to most of the racers,This would be excellent while the car in the stage lines or in between AutoX runs. BUT it WILL BE a significant drain on the battery, so I suggest you use a battery pack as well.(or keep one handy)

It was a bit of a challenge as the 3 fan relays are configured to allow a series circuit in low speed.

It will take 3 decent (30Amp) relays and should not set ANY DTCs. These arnt really complete instructions just a diagram that assumes the person doing the mod knows how to wire up relays and switches. The only impact this will have is that when the PCM commands low speed mode only fan 1 will run (but at FULL speed - should be OK) as opposed to BOTH fans at 1/2 speed due to being in series. If the engine temperature continues to climb the the PCM will command both fans to HIGH SPEED mode which is unaffected.

Those more electrically inclined please scrutinize thouroghly and if someone wants to give it a go, they can can PM me for any additional support.
Regards
WopOnTour
NOTE: THE INSTRUCTIONS AND WIRING DETAILS ARE DIFFERENT BETWEEN THE REDLINE AND THE COBALY SS (BUT I HAVE BOTH) PM OR EMAIL ME FOR COMPLETE SCHEMATICS AND DETAILS-WOP

[WopOnTour]

Originally Posted by cavingman

your gonna need to re-write these in layman's (sp) terms, or your going to get a shatload of questions from everyone. IE: this color wire to pin 87 on relay 1, this color wire to pin 87a of relay 2 etc. trust me, we did this alot on grandamgt.com

Nah, shouldnt be a problem. All the wire colors are on the schematic, once you find the S/P relay (I'll post a pic) 87a is clearly marked on the small diagram printed on the side of the relay, and it's also identified on the bottom of the relay. 87a is generally only used in a 5-pin relay and is the closed switch contact when the relay is DEenergized. Pull the relay look at the bottom, identify 87a observe where THAT leg plugs into the relay connector (should be a large grey wire) Then connect one lead of an ohmeter to THAT pin (being careful not to spread the terminal) and then touch EACH of the 3 seperate wires formed by cutting splice 156 (S156) one-at-a-time. There will be only 1 with continuity. Mark that wire, then run it to a good engine ground (add 12 AWG wire and an eyelet terminal as necc) Finally splice/solder the remaining 2 grey wires back together and re-tape.

The new relays can pretty much all be done right at the wires that are connecting to S/P and FAN 2 relays mounted on the rad. One new relay to feed the LIGHT-BLUE wire to the FAN 1 motor and a second new relay to feed the large GREY wire either right on FAN 2 or at the FAN 2 relay. Just make sure they are 30A relays and you use a seperate 30A fused 12 AWG wire for the B+ feed to the relays. (You'll need likely need a butane solding iron to get enough heat to solder these to the exisiting 12 gage wires.

The hardest thing will be locating S156. Right now I'm going right off the FSM data, (which is usually 100% for harness stuff like this) but as soon as I get the chance I will physically confirm the location.
S156 is going to be actually WITHIN the conduit/taped section of the engine harness. (see pic) So it's going to take a bit of skill and confidence, to "cut-in" to get access to this. I personally use a "seam-ripper" to open up this type of harness without cutting any of the wires, but lots of people use an adjustable razor knife to carefully cut up the gap in the conduit.

I was really trying to prevent this type of detailed wiring modification, but given the way the fan circuit was wired, I couldnt determine ANY other way to do it that would be totally transparent- not set DTCs, and not putting the safety of the engine's cooling in jeapordy. Maybe there's another way, (like using the Class 2 data line for instance to command the fans) but no solution barring keeping a TECH 2 in the car (to command the fans ON) seems obvious to me.

PM / email me if questions
WopOnTour

[WopOnTour]

Originally Posted by cavingman

caspers does fan switches for alot of cars. wonder if we could get them on this. caspers is plug and play too

Yea Caspers pretty good and been around forever. (A lot of the Megasquirt crowd use them for GM sensor connectors, terminals etc) Well maybe if we can round up the connector PN#s for the FAN1 connector and the Relay block used for FAN 2 we can make it more plug and play. BUT as far as I can see, we would still need to alter S156.
WopOnTour

[Sp00ner]

So, I'm going to give this a shot here Wop, I need to have this stuff running the whole time. It will keep things alot cooler. The intercooler was working well though. After a 1.5 min run my intake 2 temps were only around 120. That was after I got off the gas, and the temps alway climb when I get off the gas, so it was maybe 105-110. 46 degrees out.

However, staging would have the temps up to 140. We'd be sitting idling for 10 mins at some points. Having the fan on, at least, would be nice. It dosen't seem to come on until the coolant temps get pretty high, which they don't seem to do when it's colder out.

Any new tips or revisions on this?

[max_boost]

Originally Posted by Sp00ner

So, I'm going to give this a shot here Wop, I need to have this stuff running the whole time. It will keep things alot cooler. The intercooler was working well though. After a 1.5 min run my intake 2 temps were only around 120. That was after I got off the gas, and the temps alway climb when I get off the gas, so it was maybe 105-110. 46 degrees out.

However, staging would have the temps up to 140. We'd be sitting idling for 10 mins at some points. Having the fan on, at least, would be nice. It dosen't seem to come on until the coolant temps get pretty high, which they don't seem to do when it's colder out.

Any new tips or revisions on this?

Wouldn't it just be easier to wait until there is access to the ECM and then use that to turn the fans on when ever you wanted? Hell you've got access to the equipment and software to do it, just need to figure out how.

Try it on Rice's car first, he seems to like being the guinea pig

[Sp00ner]

Originally Posted by max_boost

Wouldn't it just be easier to wait until there is access to the ECM and then use that to turn the fans on when ever you wanted? Hell you've got access to the equipment and software to do it, just need to figure out how.

Try it on Rice's car first, he seems to like being the guinea pig

Well, it would be better, but I don't know about easier... Plus, I want them to be on while the car is not running... There's also no easy way to keep a laptop ready to boot up and plug in when I come off the track. A switch would be much easier.

[yrethguad]