FD fan mods

[Ranger]

Hey guys, I need some help from anyone who knows anything about the stock FD fans. Mine don't come on...at all. Obviously that's a huge problem. I'm pretty sure it's because the ECU is reading the wrong temperature (Power FC displays no higher than 33*C even after driving), but until I fix that problem, I want to wire the fans to either a) be on all the time or b) be switchable. I don't have fog lights anymore, but still have the switch, so I think that one would be perfect.

Also, I was told a long time ago that you can control when the fans come on with the Power FC. Does anyone know if that's true? If so how do I do it? That'd be far easier than modifying the wiring.

So...would any of you guys be able to help out? I'm pretty good with electrical wiring but have no experience with the fans on these cars...I don't even know where to start. Thanks!

[Ranger]

OK, so looking around a bit, I found this page:

http://rx7.voodoobox.net/howto/fanswitch/fanswitch.html

Holy crap why does everything have to be so complicated on these cars I think I will do this mod if I can't get the fans to come on with the PFC...

[rmeeker13]

I ran two electric fans on my chevelle setup like the link you posted. I just ran them off of a toggle switch with a relay.

[speedjunkie]

Do your fans come on with the AC? I just turn on my AC if my fans don't come on soon enough for my liking. I've also noticed that it seems that there is only one speed for the fans when using the AC switch, no matter if you have it on 1 or 4.

[chickenwafer]

Yes, you can make the fans come on with the PFC, but you need the Datalogit to do it. See if someone (paging Eric, haha!) has one you can borrow to load in a custom map. I can make the adjustments for you if you need it.

Wiring the fan switch isn't too difficult. You just need to bypass the group of 4 relays. Basically the switch will ground the relays, turning on the fans.

Also, you can do what I do- turn on your parking lights while driving, they will kick the fans on to the lowest speed relay. If your A/C is deleted you can just turn on the switch and the ECU will automatically turn on the fans.

I would look into replacing the coolant temp sensor, and also buy the FC Thermoswitch, which turns on the fans about 10*C sooner than the FD thermoswitch

[Ranger]

Do your fans come on with the AC? I just turn on my AC if my fans don't come on soon enough for my liking. I've also noticed that it seems that there is only one speed for the fans when using the AC switch, no matter if you have it on 1 or 4.

Dunno, I don't have AC anymore! LOL but they don't come on at all regardless of the fan switch.

Yes, you can make the fans come on with the PFC, but you need the Datalogit to do it. See if someone (paging Eric, haha!) has one you can borrow to load in a custom map. I can make the adjustments for you if you need it.

Wiring the fan switch isn't too difficult. You just need to bypass the group of 4 relays. Basically the switch will ground the relays, turning on the fans.

Also, you can do what I do- turn on your parking lights while driving, they will kick the fans on to the lowest speed relay. If your A/C is deleted you can just turn on the switch and the ECU will automatically turn on the fans.

I would look into replacing the coolant temp sensor, and also buy the FC Thermoswitch, which turns on the fans about 10*C sooner than the FD thermoswitch

Yeah, that's what I gathered. But the AC fan switch, as well as the parking light switch, have no effect on the fans. I'm positive it's because the ECU is reading such a low temp. Man, if someone has a Datalogit I could use, that would be soooo awesome. I need it for other reasons though.

Unfortunately, I just replaced the thermoswitch, and the CTS, the ones that are located in the water pump housing, so that's not the problem. Wondering if it's the sensor on the rear iron.

ALSO after looking at the wiring for my fans...it's alllll weirdjust like the rest of this car has been HAHA. The relays are completely bypassed, I can't tell what's up just by glancing at it, but it looks like they've just been looped into themselves somehow. One relay is missing as well. I don't quite understand it myself. I'm about to go take a more detailed look and take some pictures.

[RX-7 Chris]

The only way you will ever find the problem with your fan is with a volt meter. Start at the fan and work your way back.

Test the voltage to the fan (should be over 12 with the car running), also check the ohms at the ground to the fan. From there move to every connection those wires work there way through and do the same thing. Clean the grounds with a wire brush.

Once you have worked your way to the firewall, start on the wiring to the sensor. My guess is the problem is with the wiring to the sensor. The temp sensor works on resistance. As the temp goes up, the resistance goes down. If there is resistance in the wire between the sensor and the computer is to high it will make the temp read cold.

http://www.howstuffinmycarworks.com/CTS_coolant_temp_sensor.html

[chickenwafer]

If the relays are bypassed- further evidence by turning on the A/C or parking lights doesn't turn on your fans- then I can just about guarantee that's your issue.

Wiring sucks, but you're going to have to go in there and remove whatever hack job someone else rigged and try getting the wiring back to OEM as possible. I have a hardcopy of the FSM if you need it.

[Ranger]

Sounds appropriate...I only had to do that already with the entire ignition system I looked at it last night, it's hard to tell WTF is going on. It's like the wires from the fans just disappear into nothingness. I'll try and take some pics but I don't know how well I'll be able to show it.

However it's also my understanding that the fans won't come on at all if the car is below a certain temp, regardless of if the a/c, lights, etc. are on. Is that not correct? I just discovered that the connectors for the coolant temp sensor and the fuel temp sensor are likely reversed...so that's hopefully why the ECU is reading the wrong temp. Or rather, it's not reading the wrong temp...it's just reading the fuel temp

I think what they did (or tried to do) was wire the fans directly into the PFC so that the PFC can control it, regardless of what the factory ECU would be telling it to do.

[chickenwafer]

I was under the impression the A/C and Parking Lights will run the fans, but only when the t-stat has opened, or at least the ECU believes the t-stat is open. So I think it is coolant temp dependent.

If the fuel temp sensor and coolant temp sensor connectors are swapped, you should have all kinds of issues. The ECU would think the fuel is boiling more or less (since gasoline boils at a lower temperature than water) and could drastically be cutting fuel.

A really simple way to get you going, but more work in the end, would be to just disconnect the fans from the OE/jacked-up wiring and run a fused wire straight off the battery to a switch, then into the fans. This will only give you one fan speed, however, as apposed to the 3 factory fan speeds, but it will be the highest speed.

And you'll have to remember to flip that switch otherwise you'll overheat. And it's obviously a cheap band-aid type fix, but it will buy you time to tackle and remove someone else's idea of a a wiring job.

[Ranger]

It didn't run THAT bad, but...

...I swapped the connectors for the temp sensors, and wha-BAM instant fix. The PFC is now showing the correct water temp.

Strangely it wasn't cutting fuel, it was adding fuel, running incredibly rich. It was idling around around 10.5:1 A/F. I guess because it was reading such a low water temp. But no more! Now I just have to tackle the fan wiring, because they still aren't coming on no matter what. I'll try the fix you mentioned for now. Thanks!

[RX-7 Chris]

that's good. Now try what I said and use a volt meter.

[chickenwafer]

It didn't run THAT bad, but...

...I swapped the connectors for the temp sensors, and wha-BAM instant fix. The PFC is now showing the correct water temp.

Strangely it wasn't cutting fuel, it was adding fuel, running incredibly rich. It was idling around around 10.5:1 A/F. I guess because it was reading such a low water temp. But no more! Now I just have to tackle the fan wiring, because they still aren't coming on no matter what. I'll try the fix you mentioned for now. Thanks!

Sweet!

So now with the PFC reading the correct water temp, turning on the A/C still doesn't move the fans? Even when the engine is warmed up to at least 85*C?

You can do like Chris and go through a volt meter. I'm also a fan of using a wire tracer device, basically you clip a box on the wire and use a probe which buzzes when it's near the wire. It's very helpful for when you have to trace wires through a firewall or in a mess of a harness. Harbor Freight sells one for about $30 bucks.


Edit: I also just thought- do you even know if your fans work? When is the last time they ran? You can try using a battery to put 12v straight into the fan and see if they power up. All this work maybe for not if the fans don't even run.

[RX-7 Chris]

You can do like Chris and go through a volt meter. I'm also a fan of using a wire tracer device, basically you clip a box on the wire and use a probe which buzzes when it's near the wire. It's very helpful for when you have to trace wires through a firewall or in a mess of a harness. Harbor Freight sells one for about $30 bucks.


Edit: I also just thought- do you even know if your fans work? When is the last time they ran? You can try using a battery to put 12v straight into the fan and see if they power up. All this work maybe for not if the fans don't even run.

I agree, test the fans to see if they even work first.

The wire tracer's are great.

[Ranger]

Nice, I'll pick up a wire tracer. I actually didn't let it warm up to 85*C, so I'm not sure, didn't think it would need to get that hot for them to come on. They worked perfectly before I got it back from Precision though :/