[Fixed] Radiator fan always running
 

I noticed this weekend that both of my radiator fans are always on (possibly full speed) when the car is in on/run mode - both with the engine running or not. What should I be looking at to fix it?

I've tried messing with A/C controls, as apparently having the A/C or defroster on can kick the fans on. I believe the engine temperature sensor is working properly, so it's not thinking the engine is too hot and kicking the fans on to try to cool it down. Although my AiM Solo 2 DL doesn't pull the ECT data, but my RaceCaputre Track mk2 does (weird). I also pulled each of the 3 Fan relays under the hood, which resulted in one fan running and one fan not running in each of the 3 cases. So, it seems the the relays are fine unless all 3 of them went bad at the same time.

Car is 2013 BRZ limited with 45k miles and at this point is a weekend / track car. The car has been sitting in the garage for the past 6 months and I'm starting to get it ready for a track day end of the month. Stock ECU/tune with no electrical mods and stock cooling system (radiator and fans).
I also have ABS/traction control/engine lights on due to a faulty left rear wheel speed sensor, which I probably broke installing extended wheel studs over the winter. I have a replacement on order and will get that squared away as soon as possible. I checked the OBDII codes via Torque and just seeing the code for the wheel speed sensor (P0500).

Attached image of my wheel speeds: 2290.6mph... almost Mach 3! :burnrubber:

Can you pull up the coolant temp through your aim solo? Could be a bad sensor telling the car it is too hot. The sensor is hard to get to, it is on the cast aluminum crossover tube under the intake manifold.

Nope. Attached screen shots of my AiM Solo and RaceCapture screens.

Note that I am new to the Aim products - picked it up over the off season. So, I wouldn't put it past user error, but the wheel speeds seem to work fine (other than the bad sensor I need to replace).

Yea, it does seem that the likely culprit is the engine temp sensor, but why would the RaceCapture show me a value for it? The values do increase if I left the engine run a little (engine temp rises faster than oil temperature). RaceCapture is configured to use can ID 864 (0x360) offset 2 (16 bits) with a length of 1 (8 bits). Possible that AiM is using a different PID for ECT? Just trying to get my head around the failure mode that will cause the results that I'm seeing...

Thankfully, the engine temperature sensor is a $20 part. But looks like I'll need to pull the intake manifold to access it. :mad0260:

Hmmm. I would think if the fan is coming on when the car is keyed hot the sensor would be giving a weird reading. If it seems close to correct I don't think that may be the issue and you may have something else going on.

I managed to locate the engine temperature sensor and was able to pull off the connector. Put the car into on/run mode and plugged in the RaceCapture Track mk2. Got an engine temperature reading of 419 F! Note that this is 215 C and the PID conversion is "value - 40", which is means that value = 255, which is the max value of an unsigned 8-bit number. So, this confirms to be that the engine temperature sensor is working. Good thing I don't have to replace it because there is almost no room to work with there. I believe I could swap the sensor without pulling the intake manifold, but it would require a 6-pack and inventing 37 new swears to pull it off.

So, I'm leaning towards the "something else is going on"... and I'm starting to think that this might be an electrical issue. :cry:

I know the fans run when the A/C is on. I started up the DD, which is an Impreza and put the A/C on. This started the radiator fans and they shut off when I shut off the A/C, so working as expected. However, the fans were running pretty slow, whereas the fans on my car were on full blast. I could take a video of them, but the best thing in my head to compare it to would be a box fan - the Impreza is on low setting, whereas the BRZ is on high setting. Not sure this totally discounts the theory that the BRZ thinks the A/C is actually on, but the behavior seems different enough.

Not sure what it could entirely be, but if you have access to Techstream you can check two things to help you determine the issue:

1. Check if the ECU is sending the signal to turn on the fan.
2. Turn on/off the fans manually as part of testing. Once you exit testing it will run normally.

If the ECU is not sending a signal and you can't control the fan in test mode, then it's likely an electrical issue somewhere.

I do not have Techstream (yet), but I'll certainly look into it. It sounds like Techstream would allow me to determine if the ECU is controlling the fan properly. So, that would tell me if the problem is before or after the ECU.

I was also looking at the BRZ wiring diagram (https://www.ft86club.com/files/BRZwiringi.pdf - page 338) last night and from it I'm gathering that the fans are on / off and not speed controlled (which is what I assumed) as the motors are just connected to relays. So, perhaps the difference I'm observing between the BRZ and Impreza is that the BRZ has higher performance fans than the Impreza because racecar.

So, sounds like the next steps tonight are to look into Techstream. I'm also going to scour the wiring diagram to find the best place to unplug the AC to see if that shuts off the radiator fans. Might be a reverse (poor man's) test of what Techstream would tell me.

There is speed control with the fans. Looks like relay 1 and 3 switch the fans on, and relay 2 controls speed. So I would assume two speed.

Update - my vehicle speed sensor came in yesterday and installed it this evening. Ended up clearing the checking engine light using Torque and the fans shut off! So, I think this validates that the ECU can control the fans properly. I'm not calling this fixed quite yet, but this may in fact be related to the wheel speed sensor issue.

From the repair manual:
Of course, replacing the wheel speed sensor didn't do the trick. :thumbdown: However, I did notice the metal ring on the axle it reads from was slightly bent. I thought I did a reasonable job bending back into shape, but still no dice.

Anyways, I'll update the thread once I get the wheel speed sensor issue sorted.

You can edit fan functionality in ECUTEK and the values are a combination of temperature and vehicle speed. I’m glad you solved the issue.

These cars are so interconnected between all their systems and sensors that if any have failed it almost always causes issue with another system. Tech stream is a worthwhile investment so I definitely recommend finding a way to get it working for you.

So, sounds like the ECU is in some failsafe mode for the radiator fans because it 's not 100% sure on the vehicle's speed because of the wheel speed sensor issue. The connection was non-obvious to me, but it seems to make some sense now.

Anyways, spend this afternoon on the wheel speed sensor issue and learned alot (added some info to the largest wheel speed sensor thread I could find: https://www.ft86club.com/forums/show...8&postcount=34). The original wheel speed sensor tested good by swapping sides (should of done this in the first place :bonk:). Looks like the wheel speed sensor interfaces with a magnetic ring in the wheel bearing. So, looks like I'm going to order a new hub and swap it in next week

I'm just going to quote NoHaveMSG's signature, because I'm not so good at tests. :iono:

I believe you are on the right track with the wheel speed sensor. The ECU does take vehicle speed into account when controlling the fans. I would check the harness on that corner too to make sure it is not damaged. Even the insulation being pinched is a sign it took a smack and damaged the wires.

Just to bring closure to this thread. I finally fixed the wheel speed sensor issue (replaced wheel speed sensor, wheel hub, and cleared the codes in the ABS module with a ABS/SRS/Engine/Transmission + CAN OBDII scan tool) and the radiator fan is working as expected.

Thanks to all the folks to chimed in and helped me to understand the issue.