FD fan mods

Ranger · Postby **Ranger** » Fri Sep 17, 2010 9:14

So in doing some research last night, I found out the following:

- Fans do NOT come on, ever, not even approaching dangerous temps
- The connectors get some voltage, but minimal amounts (talking mV), not sure if what it should be
- The connector for the missing relay is simply not plugged in
- Tried to test the fans by applying voltage from a 9V battery but had no luck

I need to do some more research on how the relays work. But really I'm thinking I will probably just bypass the relays entirely. I'll never use the A/C or heat (neither work), and I can't imagine a need for more than one fan speed...the highest.

Postby **RX-7 Chris** » Fri Sep 17, 2010 9:14

-I assume you mean the connectors for the wiring to the fan. If it is only showing mV than it is just noise in the wires and you are basically getting nothing. The power to the fan should be at around 12+ volts.

-the fans need more to turn than 9v battery. Try conecting a wire into the fan and puting it to the positive for the car battery and see if the fan turns. It should turn within a few seconds.

this should help: http://www.garage411.com/EngineCoolingFanFD3S

I would keep the relay.

chickenwafer · Postby **chickenwafer** » Fri Sep 17, 2010 9:14

The FD uses a total of 4 relays, actually, to control the fans. The array of relays is how the PCM varies fan speed.

9V should still get a slight stir out of the fans, I would believe. But yes, go ahead and just use a car battery (12v) to try and get them moving. Make sure you ground them properly. Another problem with the 9v battery is it might not have provided enough amps to get the fans moving- fan pull a good deal of amperage.

If I were you, I would just wire up my own relay connected to a water temp sensor that automatically turns the fans at 190*F and off at 180*F. You can buy a relay with the sensor in a kit from Summit Racing for about $45 bucks or less.

Or, even cheaper and simpler, would be just a 12v wire to a switch to the fans. The problem here is you have to remember to flip the switch- the relay is basically an automatic switch (really the definition of a relay, LOL), so it does that for you. If you forget to flip the switch, you could get in trouble, and fast.

alpha · Postby **alpha** » Mon Sep 20, 2010 9:14

It sounds like you're way beyond this, but the Data Link Connector (factory diagnostic connector in all FD's) has a node for turning on the fans. It's the node marked with a star in my diagram here...

(try to ignore the dashes, the forum doesn't keep spacing correct)

-00--00-
0000000
-000000-

-000*00
-0-----0

If you tie this node to ground then the fans should turn on high.

Also, even a cool engine on a cold day should turn on the fans when you turn on the AC.

Later,
Matt

chickenwafer · Postby **chickenwafer** » Mon Sep 20, 2010 9:14

Matt, do you connect that port you marked to a GRD (ground) port in the diagnostic connector?

Yes, you are correct, the A/C should turn on the fans no matter what.

I honestly think Ranger's wiring is so molested beyond stock the only thing he can do right now is either rip out the crap and attempt to assemble the wiring back to OEM spec, or to just bypass it altogether and wire in his own relay.

Postby **RX-7 Chris** » Tue Sep 21, 2010 9:14

Wiring diagram: http://foxed.ca/rx7manual/manuals/Z-large.pdf
page 6 has the wiring color code and page 45 is the diagram for the fans.

Fan 1:
yellow with white to relay 1
red with yellow to relay 2
black to ground
yellow with orange to relay 3

Fan 2:
yellow with white to relay 1
white to relay 4
black to ground
yellow with orange to relay 3

Ranger · Postby **Ranger** » Sat Sep 25, 2010 9:14

Finally got around to doing some testing. The fans DO work. And, I discovered they come on at 100*C. Pretty dangerous. I also discovered that I should never turn the a/c on, because if I do, it makes the car idle around 1800 RPM, and you can't get it to stop doing that :lol:

Oh well, I'm still not sure if I want to try and fix the factory wiring, or just wire something up myself. But at least this was a step in the right direction.

chickenwafer · Postby **chickenwafer** » Sat Sep 25, 2010 9:14

Well that's good news. The factory thermoswitch, which controls what temp turns on the fans, is set at 106*C in the FD, which is just crazy. It's a common swap to use the FC thermoswitch which will kick on the fans at 98*C IIRC

Ranger · Postby **Ranger** » Sun Sep 26, 2010 9:14

That still seems way too high to me, haha. I'd rather see them come on somewhere around 90*C. I was seriously panicking, thinking it was going to overheat (the temp was rising rapidly), until they finally came on and the temps went back down to 95*C or so. Yesterday wasn't even a hot day, either. If I ever have the thing tuned, I'll be sure to have the tuner lower the point they come on. It's too bad you can't do that through the Commander...

chickenwafer · Postby **chickenwafer** » Sun Sep 26, 2010 9:14

Oh no, I agree, it's WAY too high. The fans don't kick on until 221*F, and I would consider your rotary "overheated" at 235*F. At those temps your water jacket o-ring is pretty gone, or you just severely shortened the life of the rubber. At 245*F you could warp plates and apex/side/corner seals.

So I agree, the fans should really kick on by at least 190*F.

alpha · Postby **alpha** » Mon Oct 04, 2010 9:14

chickenwafer wrote:Matt, do you connect that port you marked to a GRD (ground) port in the diagnostic connector?

Any ground will work for this test.
Matt

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