[zroger73]

It sounds like the cooling fans are randomly toggling between low (or off) and high speed. The first thing that comes to mind is a faulty high-speed fan relay. Other possibilities include a faulty powertrain control module or refrigerant pressure switch.

1. Do the fans do this only when the climate control is on?

2. How about with the climate control is off and the engine is idled long enough for the temperature to rise to the point where the fans would normally turn on high and stay on for several seconds or more?

 

[zroger73]

Could be a worn out clutch fan.

Like most vehicles since the 1980s, the Ridgeline has electric cooling fans so there is no fan clutch.

 

[zroger73]

I listened to the video again with high quality headphones. From the sounds, I can determine the following:

1. The engine was idling the entire time without being revved.
2. The climate control was on (because the compressor clutch can be heard at 0:27).
3. Prior to 0:27, the fans were cycling randomly and quickly between off and high (abnormal operation).
4. At 0:27, I heard the A/C compressor clutch engage and the fans turn on low speed (normal operation).
5. After 0:27, the fans continue cycling randomly and quickly, but between low and high instead of off and high (abnormal operation).

From this video, all that can be concluded is that the fans are cycling abnormally and quickly in and out of high speed. The next step is to determine if the PCM is commanding the fans to high speed due to a sensor problem or if they are "doing on their own" due to a faulty output in the PCM or fan relay. An electrical diagnosis (preferably by a dealer with a Honda scan tool) is required to further determine the cause of the problem.

This could be as minor as a fan relay, refrigerant pressure sensor, or engine/coolant temperature sensor or as major as a PCM.