the trick FM uses on the hydra is to wire it to three ECU pins. Fan A, Fan B, A/C. There's a diode from Fan B to A/C to prevent the fan from engaging A/C the A/C clutch but you get the ability to run two-stage fans or have the fan come on with the A/C.

 

Goal: Have first fan stage circuit excite at 175 F. Have second stage fan circuit excite at 206 F. Do not interfere with A/C control over pass side fan.

Result:
engine temp < 175 F = No fan
engine temp > 175 F & < 206 F = Single stage fan
engine temp > 206 = 2 stage fan (both fans running)
A/C on = A/C fan on, regardless of engine temp

Required items: SPDT relay, primary wire, crimp connectors, electrical tape, 30A fusible link

Instructions: The relay has 5 positions, wire as follows
Pin 30 to A/C side fan black/blue stripe wire FAN SIDE OF WIRE
Pin 85 to thermosensor
Pin 86 to +12V
Pin 87 NO to +12V (high power)
Pin 87a NC to A/C side fan black/blue wire on the CAR SIDE OF WIRE

You need a real automotive SPDT relay with a true NO contact and a true NC contact. The el cheapo $1.49 relays probably won't cut it. It should run $7-10.

You can grab +12V at the underhood fuse box. There are a variety of places. I had an unused position, so I crimped a spade connector onto a 14ga wire, and inserted it into the bottom side of the unused positon. Then reinstall the fuse block and insert a 30A fusible link. *(I ran this wire to both pin 87 (high power input) and pin 86 (switched 12V) so that my relay had power full time. If you wanted the relay to only work key on, you would need to run a switched on +12V source to pin 86.)

The A/C side fan has 2 wires. Leave the black wire alone. Cut the black/blue stripe wire. The side of the wire that goes to the fan connects to pin 30 on the relay. The side of the black/blue wire that comes from the car goes to pin 87a on the relay.

The thermosensor on top of the thermostat housing has only one wire. Cut it and bring it to pin 85 on the relay.

Tape everything up and make sure all your wiring is secured.

Enjoy

 

My temps generally dont hit 190 but i like this mod. i might try something similiar

 

You have a problem if your CLT never gets to 190.

 

nope my fans would rarely come on before while driving and did not come on to often at idle either now that the fans are set to 175 degrees i stay around there wich is fine running hotter than that is a waste. I try to avoid 200+ degrees at all costs i run 35 or so % antifreeze. I also run a 160 degree thermostat I will continue to log now that i have MS if i have any problems i will swap to a koyo or something similiar. but without a FMIC i dont for see any problems.

 

Problem with fan mod addressed. Mod is successful.

 

Where do you change the fan turn on temp in MegaTune?

 

Under 'More Settings' > 'Outputs'

You'll see the lower output, #2, is set to activate on CLT, and the default temp is 215. Note that it actually activates 40 degrees under whatever this is set to, notice the note on that screen (F+40). So this is really activating the fan at 175 degreesF. You could raise it a bit if you wanted, I believe stock doesn't activate until 197*F, but I wanted to have it default a bit lower.

 

I believe stock is 207°F, but I could be wrong.

 

We need a commons MSPNP mod faq/thread

 

we have the beginnings of one already stickied in the ms section. just add to it.