Left Lane, jumping back to what 05YellowGt was saying, do you have a handheld tuner that came with your car (like a SCT or Diablo), or a OBD II bluetooth adapter to see what temps the car's PCM is actually seeing? According to the wiring diagram, it uses the cylinder head temperature sensor in the right rear of the engine as one of the inputs to the cooling fan circuit. It'd definitely be beneficial if you could see what the PCM is using.

If you have one like the SCT, you can do data logging and see whether the high speed or low speed fans are being commanded on by the PCM.

Without a scan tool, you can still try tracking it down the old fashioned way with a multimeter. In the fuse/relay box under the hood, you have separate relays for the high speed and low speed fan circuits. Relays #25 (high) and #28 (low). According to the owners manual, you're not supposed to go probing around in there at the risk of damaging something. I did and didn't break anything, but do at your own risk. When the computer commands a fan circuit on, it'll apply +12V to one of the low current pins (either 85 or 86 -- they're labelled on the underside of the relay) on the relay to energize it and close the high current circuit.

You could probe one of those pins but again, factory manual doesn't recommend it and if you're not used to probing circuits I probably wouldn't do it either.

Option B would be to just listen for the relay clicking when the circuit is supposed to come on. You can pull the relay and plug it back in and should hear/feel the relay actuating when it's connected/disconnected.

You can also check power at the plug to the radiator fan. Unplug the plug and check it with a voltmeter to see if you're getting +12V (or ~14 when the car's running) at the correct pin. The green wire with the purple stripe is the high speed circuit. The green wire with the yellow stripe is the low speed circuit. Of course on mine, there are two green/yellow wires, but the one of the same side as the green/purple wire is the one that gets power (no idea what the other one is hooked up to, if anything -- I only see one on the wiring diagram)






For me, since I'm getting power all the way to the plug, I know its something on the radiator fan. Maybe the low speed resistor.




High speed circuit hot



Low speed circuit hot

 

Thanks for all the info! I'll definitely go get a multi meter. I don't have a hand held tuner, I have a custom dyno tune. Also no bluetooth obd2 scanner, I heard somewhere they can potentially mess things up so I just never bothered to look into them. If that information was wrong I'd love to get one. There's no chance of it messing with the tune or anything right?

 

So I was doing some more testing and just sat there with the ac on for quite a while and the fan never turned off. I read somewhere that over 45 mph the fan will turn off because at that point there's just more flow with the wind passing through the grille. That would explain why it turned off after I went for a drive (don't know if it should have come back on though once I stopped moving). Anyone know what sensor it is that tells the fan to turn on? I know these cars don't have coolant temperature sensors, but they use cylinder head temp sensors. I'd like to test the sensor that tells the fan to turn on, but if its the CHT sensor I won't bother. For anyone that doesn't know, that's under the intake manifold. I'll wire up a standalone system before I take the engine apart.

 

My '13 5.0 has a temp sensor in the radiator shroud. Not sure if the 4.6's were the same.

 

I don't see any sensor there, anyone else? Did more testing today and noticed the fan will stay on as long as a/c is (at least when I get out and check, don't know if it is while I'm moving but that doesnt matter). I let my temps get to 205 today and ran the a/c while idling in the a parking lot and temps dropped to 200. I'm happy with that for now

 

According to the wiring diagram, it uses the CHT sensor on the right, rear of the engine. Also uses a pressure switch in the front left Of the engine bay. Those Bluetooth adapters shouldn't hurt anything if you want to pick up one from Amazon on the cheap (probably good idea to check the sellers return policy if it's a cheap one you get)

 

Well that's depressing to hear. I'll look for the pressure switch and hope that's what it is. I'm going to my tuner tomorrow for my speedometer (changed my tire size) so I'll have him look at the temps it's set to come on at. I doubt that's it but might as well while I'm there lol

 

Just curious as to why you don't have a tuner with your custom tune on it? My car has been supercharged with a custom tune since shortly after I got it, and the tune is on my SCT tuner which I can also use to change tire size and such. I can also change parts of the tune, although I only did that when I first got it while it was still N/A. If you tuner doesn't want you changing the tune he can lock you out of that, but let you change tire size, gears and check or clear trouble codes.

 

Didn't have one when I bought the car I guess lol. My tuner's name is Tony Gonyon (being in Florida, I'm sure you've heard of him) so when I need something tweaked I just give him a call. It definitely would be more convenient to get one, but they're pretty expensive for a convenience.

 

Thanks everyone for all your replies and ideas, my problem is solved. It was a mix of issues but nothing really wrong. First off, the person that installed my temp gauge before I had the car installed it in the upper radiator hose. Since that is right when the coolant comes out of the engine, it's hotter than the coolant that is currently in the engine. That makes the temp that I'm seeing hotter than what the computer is seeing. When I saw 220, that was higher (not sure how much) than what it actually is, so it hadn't gotten to the temp for the fan to actually turn on. I never let it get past 220 because I was being cautious. Tony turned my low setting down to 191 on, 189 off, and the high speed to 195 on, 193 off. Everything's working nice and good now. Thanks again for all your opinions and suggestions

 

Also my a/c compressor is ****ed but I don't use it so I don't care lol