Ayotriple

I know some of you guys/gals are running electric fans but how do you have it wired up? I’m trying to install a set of IS300 fans and have them triggered on by the ecu. Currently I have a 16” Spal but it’s wired straight to ignition power so it pretty much is on the entire time the car is on.

I’ve looked up threads to see if anyone knows which wire I have to splice into so the fan turns on via the cooling fan ecu. Any help will be greatly appreciated.

KahnBB6

iTrader: (5)

You must be using the PHR aftermarket metal shroud to house those IS300 fans in your SC?

I have not used these fans myself but I am familiar with wiring up auxiliary fans.

They are heavy duty cycle fans so they can be run for a very long time without issue but they should still be set up to run in a normal low speed mode for normal demand and a cycled high speed mode for extra cooling demands.

PHR makes a harness for $300 that includes seemingly everything necessary to run these fans in their normal constant-on low speed mode and then in high speed mode using the pre-existing A/C pressure switch in your SC as the trigger.

Also read these threads for further info:

https://www.supraforums.com/threads/.../#post-9031857

https://www.supraforums.com/threads/...#post-13164474

Ayotriple

thank you for the help I did purchase the PHR dual fan relay PnP kit and I see where everything plugs into but there are 2 wires that im confused on. This is what their instruction says

“Red: 12V switched. This can be wired in at PIN A31 on the ECU Connector.
Blue: Turn on, this should be wired to a low-side output (ground) from your ECU to activate the fans and turn them on. “

I’m not sure what PIN A31 is on the 1UZ ecu and I’m not sure what low side output from the ecu to pin the blue wire to…

KahnBB6

iTrader: (5)

I'm not familiar with what ECU pin is being referred to in the instructions from PHR and I have never installed their IS300 dual fan kit but I will try to help as best I can.

All they're asking for is a 12V Switched trigger signal, correct? And then they want a "low side input" aka ground to turn on the fans. I'd really have to see their wiring diagram for the PnP harness they sell to fully understand how they want this to be wired up and with what ECU application they have in mind... but you can technically wire up both of those functions by designing your own 12V Switched feed from a custom relay installation and the same for the switched ground signal wire that they also want. I recommend using some excellent OEM-quality parts from the Littelfuse catalog (which you can purchase piece by piece from Mouser Electronics).

You will have to take some creative inspiration of your own with how YOU want to assemble and wire up these DIY Littelfuse mini fuses and relays inside the small housings and you'll need to make your own mounting brackets from scratch just as I did but I found these to be excellent quality compact solutions to installing some custom circuits in my engine bay for my auxiliary fans and some other functions.

https://www.clublexus.com/forums/bui...l#post10976534

https://www.clublexus.com/forums/bui...l#post10976542

https://www.clublexus.com/forums/bui...l#post10976546

In your case you will be wiring up your IS300 fans a little differently since you will need them on in low speed mode 100% of the time that the engine is running and then you'll need them to kick into full speed mode whenever either a coolant temp sensor or the A/C triple pressure switch (or both in the same circuit) act as triggers for high speed mode.

There is a provision in the bottom of every Supra MKIV style aftermarket radiator for a coolant temperature sensor or switch. See further details on that sensor and how to either plug up the location or adapt it to an NPT style coolant temp sensor/sender in this older thread:

https://www.clublexus.com/forums/per...0-5-speed.html

As for the A/C refrigerant pressure switch, every SC already has one of those built in and there are two unused terminal locations on the factory sensor that can be populated by OEM terminal wires. By Toyota's design, what the OEM A/C refrigerant sensor does break the circuit when the pressure is too high but... when the refrigerant pressure is NOT too high it keeps the circuit complete/flowing.... so keep that in mind when considering incorporating it into a trigger circuit.

See the thread link below for that:

https://www.clublexus.com/forums/bui...l#post11040173

....

That all having been said, in order to better evaluate what PHR wants in terms of wiring with a method that uses ECU pins as triggers and an alternative method that does not use ECU pins, their circuit schematic for their PnP harness would be helpful.

Edit: No diagram from them but here's the PHR dual fan installation guide link that you sent me:
https://www.powerhouseracing.com/top...t_installation

Unlike auxiliary fans these need to be wired up to preserve the intended operation for normal/low and cycled/high modes with the IS300 fans.

Then we'd need to look at the SC400 wiring TSRM showing the location and function of each pin on the ECU "A" and "B" connectors would be good in order to verify exactly what they are suggesting be done.

Also, as their IS300 fan setup is intended for Supra MKIV's I'm going to guess that the ECU connector pin location that they are referring to corresponds to an MKIV 2JZ-GTE ECU pinout. Therefore with the *intended* function of the ECU pin that they want used we would need to translate that for the equivalent ECU pin with the same function for an SC400 ECU... since you're doing this install into an SC400.