CX/GL 650 Radiator Switch

Here are a couple of PRELIMINARY wiring diagrams for the electric fan and relay conversions I'm working on now. Some changes are to be expected during installation as the kinks get worked out.



My intention is to put together a detailed writeup on my web site when the installations are finished. In the meantime, this information may be of some use to you now.



Here is the relay selected for my own use. Others will certainly work fine, although I think it is worthwhile to select one with a resistor across the coil or else add your own resistor. The relay is physically located under the seat.



The diode is a good idea but not essential. It will help prevent large voltage transients. Its part number is TBD.



The manual fan switch is located either on the handlebars or someplace on the fairing. It can be used to force the fan to come on. It may be eliminated if the lower temperature fan switches prove to work out well.



For the GL500, the fused switched accessory power feed is from the spare accessory power connector located under the seat. Not all GL500's have this connector, but my bike does. The frame ground connection point is the one located under the seat - another ring terminal is added here.



P1 and P5 are both located under the fuel tank, just in front of the carbs. P1 is the right side and P5 is on the left side.











Hope you find this preliminary information helpful.

If you really feel you need a relay, ...



Yes, I do.



I've experienced a 650 ignition switch failure and have disassembled several others that showed evidence of overheating and arcing. In contrast, the 500 ignition switches rarely seem to fail. The single major difference is the routing of the electric fan power through the ignition switch. Wiring in a relay is a simple and effective fix.



Re lower temperatures: As I have said before, if the engine is not allowed to come up to its optimum operating temperature, it will burn more fuel and produce less power.



We are in complete agreement.



Regulation of the engine coolant temperature should be controlled by the thermostat. If a higher engine coolant temperature is needed then a higher temperature thermostat should be used.

What is the reason for the resister on the relay and the diode on the fan circuit.



These provide protection from high voltage transients that result when current is abruptly interrupted in an inductor, specifically the relay coil and fan motor.



The snubber diode is for the fan motor.



The resistor is for the relay coil, see here. As described in the article, it is important for the current in the relay coil to decrease rapidly so the contacts can open quickly and not "tack weld."

I understand the point regarding coolant temperature in the radiator but don't believe it's a significant factor with a properly operating thermostat.



Both the 500's and the 650's register at approximately the same point on the temperature gauge at highway speeds. The measured temperature is being held relatively constant by the thermostat - in this situation the 650's fan is not operating at all. Hopefully the Honda engineers ensured the engine is operating at its optimum temperature in this case, since cruising down the road is the bike's normal operating mode.



It's only when there is insufficient airflow that the 650's temperature rises, and finally the fan cuts on.



It would be interesting to instrument the cooling system with thermocouples to see what the coolant temperatures actually are at various locations inside the engine, with both standard and lower temperature radiator switches.



Lacking something like that to provide hard data, nobody really knows for sure if it is an issue.



My opinion, and it is just an opinion, is that it's not an issue.