Electrical and Cooling system question(s)

**Richard Buckingham** · March 29, 2015, 11:31 PM

Hey guys,

my radiator fan quit on me today on my 2012 SRA (K24) I was out on track and it was a hot 90F+ day at the time and I got the 200+ Water Temp alert which normally goes away if I back off a little but it just kept climbing. In the short time it took me to get to the pits the water temp was already up to 278F. I am hoping it's just a fuse but I've not had a chance to troubleshoot it.

Some problems/questions though for this admittedly novice tech (car is in storage 15 miles away making it tricky for me to just go check it out whenever I want):

1) anyone have a fuse diagram for the US Atom3 or SRA (I'm assuming/hoping they're similar if not identical?) Would the fan use a relay too?
2) If its just a fuse do I potentially have a wiring problem to look into? (Grrr.)
3) anyone know if the SRA uses an electrical or mechanical water pump (or both)? How do I know when it's working (or broken) would I hear it? (not that I think thats the problem but I'm wondering what I have.
4) any guidance on flushing and maintaining coolant? The manual says to top up with water only but if I fully drain the system do I first fill it with a 12oz bottle of Water Wetter and then top up to the max fill line with distilled water?

**John Scherrer** · April 3, 2015, 10:54 AM

It's often caused by a piece of tyre rubber that gets trapped between the outer edge of the fan blade and the shroud/surround. As the motor is stalled, it draws too much current and blows the fuse. It draws a lot of current so has a substantial fuse and relay to protect the circuit.

Hopefully it's just the fuse, but sometimes the fan motor gets burned out before the fuse goes ..

**MadMaxAtom** · April 4, 2015, 05:03 AM

Why do the Atom3's have the fan in front of the radiator?The 2's were on the backside and never an issue,and there is plenty of room to mount it behind,plus it looks better.

**Richard Buckingham** · April 12, 2015, 11:58 PM

Update: I confirmed the radiator fan and cooling fans alone are functional, all fuses are also good but I replaced one of the relays "just in case" (as I know not how to test a relay.) I pulled a ton of rubber out of the fan but I can't be sure that was a factor because now I still have the same problem I had after pulling of track: the water temp still reads a constant 278F on the dash. Even from cold when I just power on the electrics it's reading 278F. Have I killed a sensor? Would it fail like that and show a fixed high reading? This leads to the possibility that in fact the fans are and were always fine and it's just a faulty sensor reading now. So now I have more questions... such as:

1) are there multiple coolant temp sensors? There appears to me to be two different things attached to the coolant hoses, one directly behind the fuel tank where the hose comes up from underneath the car and the other another foot higher up closer to the engine outlet. Could it be one is just for the dash and another one is used to determine when to engage the radiator and oil fans?
2) based on that possibility should I run the engine until it's hot and see if the fans still come on? (or is that too risky a thing to do)
3) which sensor is the one to replace and what exactly is it so I can buy a replacement (assuming it's the sensor and not some kind of wiring/connection issue.)

*sigh* racecar ownership is stressful when you're not a mechanic. Happy to hear anyone's thoughts (yes I know I should take it to a professional!)

**MadMaxAtom** · April 13, 2015, 04:55 AM

If the dash is reading 278 degrees with a cold engine..the sensor is bad,or wiring is crossed. Yes,there are two sensors..one for the dash gauge and one the ECM (engine computer) uses to determine engine temp to alter injection/timing/ and turn fan on. If the engine were actually running at 278 degrees, it would be puking coolant...

**Richard Buckingham** · April 14, 2015, 08:07 PM

It was just a bad connection (loose wire in the connector attached to the sensor.) Rather than try to fix the connector I wanted to source a replacement but weirdly that connector appears to be a Bosch Jetronic "EV1" which is used typically for fuel injectors? So I'm sourcing a replacement on Ebay and I'll splice it in.

I connected to the OBDII port and verified that the other sensor is still functional, ran the car up to 200F and the radiator and oil cooling fans spun up so everything else on the car actually appears to be fine!

**MadMaxAtom** · April 14, 2015, 08:12 PM

^ Atom owners get to learn a lot about their cars..like it or not...

Glad you found your issue..

**cvjoint** · March 12, 2018, 01:22 PM

Lost the front radiator on track last weekend as well. I found a bunch of tire shrapnel holding the blades still. When I removed the rubber the fan still didn't kick on. Car was cooling fine without radiator (holding about 200*) unless with engine running with the car stopped on grid (215*). It seems like we could run the SRAs without fan if we really wanted to but we'd have to shut the engine and turn on just before heading out.

Anyhow, will troubleshoot and post up for reference.

EDIT: replaced fan and the car worked fine one track day. The next track day the overflow cap failed. TMI now sales a machined metal adapter that allows for a more rugged all metal radiator cap. The adapter also has a provision for running excess fluid through a hose for dumping under the car. With the old plastic cap it dumps right over the engine when there is too much liquid, to high psi, or the cap fails. I HIGHLY recommend an upgrade to the TMI machined adapter plus metal overflow cap.