My OLD fan wasn't working -- bridged power to it and was not working so I replaced it.
NEW fan was not working -- bridged power to it and it would work.

A: My radiator fan (and AC fan) won't kick-on unless...

1. ...I bridged power to the fan directly (both fans function).
2. ...I bypassed the relays (both circuits function).
3. ...I detached the temperature-sensor connector and bridged the circuit and turned the key to [ON] (both fans activate).

B: Oddities

1. I have not had any overheating issue at all.
2. The A/C is no colder then the fan set to "cool". *This is what prompted me to test the fans in the first place.
3. The A/C does not activate any fans.
4. I can activate the A/C clutch manually at the relay.
5. A few times, after driving awhile, I have checked to see if the fans would run at idle. So far I have not seen the fans run without myself bypassing something to force it on.
6. The ODB Torque App shows a coolant temperature of 88 to 96 degrees Fahrenheit after some 5 minutes of driving. Same thing while driving on the highway.
7. I've noticed that the temperature gauge (on my dash) will not settle at 50% but slightly less (around 35-40%). While warming, the dial does slowly raise as you'd expect until around 35-40%. I know it was half way less than two months ago.

C. Relay circuits. I tested the relay circuits according to this tutorial: Part 1 -Radiator Fan Relay Test (2001-2005 1.7L Honda Civic) It states that, while the car is [ON], to test for power on circuit #3. However, I found it was powered on #3 and #4 for both the fan relay sockets but not the horn. Not sure if that means anything but thought I should mention it. EDIT: I did confirm that #3 and #4 are unpowered while the ignition is [OFF].

Any further tests I can perform? I'm at a loss.

Edit: When I replaced the Radiator Fan, I did have to do a partial coolant flush (drain ~1/2 to remove upper radiator hose & refill after).

Edit 2

• Just checked the voltage going to the ECT (Engine Coolent Tempeture) sensor: 0v with iginition [OFF] and 12.13v with ignition [ON].
• Error Codes: Since before these issues, I've had the error P1457 (small EVAP leak) and within the last few days (after the above issues) received the error P0138 (HO2S Bank 1 Sensor 2 Circuit Low Voltage).

 

I replaced the thermostat and radiator-thermo-switch.

SOLVED: The temperature gets up to 208 F and then the radiator-fan (and condenser-fan, oddly enough) kick on for just a minute (while idling) until the temperature goes down to 194 F.

 

Sounds like the thermostat was stuck open.