My 2019 Honda Fit Sport was having sluggish launch after warmup, but not when cold. When i would turn on my AC, i could see both fans run for a few seconds, then stop for approximately 30 seconds, and then repeat. I have a Lufi XF revolution gauge that shows coolant and cvt temps, and after a lot of in town driving(I am a delivery driver), my cvt temp would rise more than 10 degrees above my coolant temperature, and would be noticably sluggish when pulling out into traffic. I discovered that running my AC for a few minutes, after turning it off, my CVT temps were lower and the sluggish launch from a stop improved. After finding an Alldata wiring diagram online i discovered that the fans are designed to run in series at half speed except when the AC is on, but my fans were both on in short bursts when the AC was engaged. After my jumper mod, the main fan comes on full speed whenever the AC is engaged, even when cold. I first planned on cutting the green wire on the main fan and running the green wire from the fan connector directly to ground, bypassing series fan operation, and forcing the fans to run in parallel, as they are supposed to only when the AC is engaged. The jumper solution is far easier, and easy to undo by reinserting the fan control relay. I also noticed far less load on my alternator, as my Lufi gauge shows lower voltages now except when an electrical load like brakes or headlights cause it to rise. It seems ecu mismanagement of the fan control relay is the issue fixed with the jumper bypass, the relay itself tests fine but wasn't activating properly. I hope this helps anyone having cooling problems or sluggish CVT operation, and I highly recommend getting the Lufi XF revolution gauge, monitoring your CVT temperature is amazingly useful as well as all the other cool features.

My fit may have been miswired at the factory, I've studied the wiring diagrams and cant explain why my main fan, which is the one closest to the battery, is active instead of the passenger side fan. When i pull the 30amp fuse for the main fan it stops, so the main fan power circuit seems wired correctly. I am thinking maybe the relay control wires got swapped between main and sub fan, regardless i Am happy that the fans will always run at full speed when they are activated, and i may be seeing a 1mpg increase in economy, more driving will be necessary to confirm that I'm now getting 37mpg while delivering in town instead of 36. I regularly get 47-51mpg on my 7 mile drive home from work at 45-55 mph. I discovered all of these problems when we hit record temperatures here in the Portland, Oregon area and saw my CVT temperature rise to 219, and my coolant temperature over 210. I'm confident now that my fit is ready for steep hills, heat waves, and towing after this simple fix.

Jumper installed between terminals 1 and 2 where fan control relay was removed

Closeup of jumper

Fan control relay. It is the only relay with 5 terminals, mine is grey on top and blue on the side, was the tallest relay, and in the bottom right corner of the under hood fuse box viewed from the front

Short 16 AWG jumper

Lufi XF Revolution gauge showing improved CVT temperature after Fan Control Relay bypass mod while driving in town about 30mph with outside temperature of about 70F

Temperatures here in July causing my CVT temperature to rise to the top end of the safe range, your CVT fluid should normally be between 190F and 210F, although i have found 180-190 gives the best economy and performance without the sluggishness i experienced, and especially would notice if the CVT temperature would rise more than 10F above the coolant temperature.

CVT at 12F above coolant temperature, always caused sluggish CVT operation, noticeable upon acceleration from a stop.

Almost 50mpg on a trip home from camping even with low pressure in one of my tires 😂

 

The correction for a cold sluggish start? You may have lost me in this tread but try relearning the trottle body valve.