The Best Jeep JK Radiator Fan Upgrade is just a laptop away.

The temperature control problem that lead you to look for a Jeep JK radiator fan upgrade. 

The 2012-2018 JK has some interesting "features" that might just surprise you. For example, the temperature gauge in the instrument cluster will indicate perfect coolant temperature way up to 232° F. This means when the needle leaves home (dead center), you're in some hot water. So, if yours has ever drifted right of center, you've had a VERY hot engine. In fact, if you just let a JK idle, the fans won't come on until the engine reaches 226°F! For this reason, I'll bet you need a radiator fan upgrade that isn't a fan at all. 

As it turns out, upgrading your Jeep JK radiator fan is best done with a laptop, not a whole new fan! The stock 3.6 JK fan can move a lot of air when it is told to do so, but the original control set points are terrible. Fortunately, this is easily corrected with an engine tuner. To explain, the radiator fan speed on the JK is controlled via pulse width modulation (PWM) from the totally integrated power module (TIPM) via setpoints in the powertrain control module (PCM). For this reason, you can't just swap out a thermoswitch screwed into the radiator like you can on most old cars. As a result, this change needs to occur in the PCM. Fortunately, there are several tools that can accomplish this, and we chose to use HPTuners.

Changing the cooling fan set points is fairly easy

You'll need to find someone with HPTuners, or you can purchase the MPVI3, and then update the fan control temperature set points yourself. If your JK is 2012-2014, you'll need the MPVI3 along with 2 credits to save the changes. If you've got a 2015-2018, you'll need your PCM unlocked too, which HPTuners can do, so long as you mail in the PCM and pay the required fee. In our case, we're running a 2014 MY PCM, so we did not need the unlocking service. 

Stock temperature set points are a bit alarming

The stock JK fan temperature set points are insane. Even with the temperature sender in the back of the head, which also happens to be the exhaust manifold, having medium and high speed settings at 230° F is ridiculous. Given these points, we most likely lost our first engine to heat, and these settings likely played a part in that failure. As a matter of fact, here's a screen shot of the factory settings:

How about some more reasonable set points as the ultimate Jeep JK radiator fan upgrade?

We've studied this a bit, and found many have successfully done this mod. We decided to do the same, but use different fan temperature setting. Running a gasoline engine too cold prevents it from boiling off water suspended in the oil as a byproduct of combustion, so occasionally exceeding 212° is a good thing. Also, as mentioned before, the temperature sender is in the hottest part of the engine, so a reading that's slightly higher than other vehicles is to be expected. Now, we don't want to see the thing get to 230°+, so we did the following: Set the medium and high speed ECT to 219°, Low speed to 208°, and the PWM Desired ECT to 212°. This prevents the nasty peak temperatures we used to see while crawling, but doesn't run the fan constantly like lower settings can.  See the changed fields in red:

Our experience so far

We found this to be the single most effective change to improve coolant temperatures in our Jeep during most lower speed driving conditions. For example, our coolant temperature now hangs out around 212°-216° F. We used to see engine temperature climb to as high as 240°+ with the stock settings, and now the highest we've seen is 228° . Keep in mind, a stock JK just sitting at idle won't even kick the fan on until it reaches 226°. Unfortunately, this won't solve coolant temperature problems during high speed, high altitude hill climbing, but it will operate properly when crawling and under all other normal driving conditions. We did a few physical modifications to remedy that high speed high altitude overheating, so the Jeep now operates as desired.