I put a digital temperature gauge in my 2013 sport. It's mounted on the lower dash just above the console. I installed it for under $40.00. Best thing I think I've done on my car for peace of mind. The components can be purchased on Ebay.

My car runs between 174-200 degrees fahrenheit and is affected by the outside ambient temperature and whether the car is moving and has air running through the condensor cooling it. The radiator temp sensor will turn the regular electric fan on when the coolant temp reaches the high 190's. If you're running the a/c, the a/c fan will stay on and help keep the engine cool. The regular fan will go on and off depending on coolant temperature.

To address your basic question of how to know if the system is working. You actually won't know for sure without a temp gauge. With a salvaged radiator and a questionable plug-in connector you can't be sure of it working properly at all, or if a signal will get to the overheated symbol on the dash when it does overheat. In my opinion, all you can really do is listen for your fans going on and off.and make sure the radiator and overflow tank have coolant in them, and hope for the best.

Basically Honda cheaped out on these cars and omitted the temp gauge that was on all Hondas for many years. Now, without installing a temp gauge on these cars, you're basically waiting for the dash temp gauge to come on if there's a problem, to let you know your car is already overheated.....

 

You could also get an OBD II port gauge reader for maximum simplicity:

* ScanGauge II (I own one and very happy with it. It's the most expensive option, but well worth the extra cost. Mine is 4 years old and going strong).

* UltraGauge

* one of dozens of Bluetooth models that connect to your phone

 

 

Yeah,,, OBD II

ELM chip.....

by Panlong...... they are like ten or twenty bucks and grab and App......
Trying to think which one I have... he app was like 5 bucks.....
I grabbed one called Torque.......

 

 

The a/c fan comes on when you turn the a/c on. Turn the a/c off and that fan goes off and stays off. The other fan is thermally controlled by a temperature sensor. When the coolant reaches the mid to upper 190 degree range fahrenheit,, the temp sensor turns the primary fan on and off to keep the coolant cooled down to a temperature under the temperature the sensor is set to come on at.

To confirm which fan is which, turn your a/c on before the engine gets hot and the primary fan comes on. The a/c fan should come on and stay on as long as you have the a/c on. This is probably the fan you say hasn't come on yet as far as you know.

Consider putting some kind of gauge in your car. whether it's a scan gauge or a regular gauge and you won't be guessing whether the system is working or not.