Honda's older, simpler rad fan switch

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Honda's older, simpler rad fan switch

A certain number of older Honda models (we're going back to 1991 and before, here) don't have the more complex relay system that newer ones do. The fan itself does have a relay similar to the one in the link above, but the switch does not.

The fan switch therefore carries full current, and eventually fails. Also, some are in an awkward spot, very close to the oil filter. Less-than gentle filter removal/installation, or the use of a too-bulky tool, will break the switch connectors (ask me how I know...).

The switch operates by closing its contacts when the coolant temperature gets above 194F (90C). When the contacts close, the fan comes on. If your fan is not coming on even as the gauge needle rises above its normal full-warm position, chances are the switch is bad. You can test it by warming the car up until the needle begins to rise past normal full-warm, then connect a voltmeter between the terminals. If you have no connectivity, the switch is bad, or the connectors are damaged. It's also possible the fan relay is bad, and that can be checked according to the link above.

Once again, the guinea pig is my Integra.

Here I'm under the car, my feet towards the front bumper, head towards the trunk. On my car, the oil filter is on the rear of the block, as is the fan switch.

If you look reeeeeally closely at the arrow for the fan switch, you'll see the two blue crimp connectors with white grease smeared on them. Beside that is the black rubber boot for the oil pressure switch (also easily damaged). The fan switch used to have a rubber boot, but I had to cut it off in order to replace the connectors.

Replacing the switch is simplicity itself, except that coolant will being spouting from the block once you unscrew the old switch. Loosen the old switch most of the way, hold the new switch close at hand, and quickly remove the old and pop in the new. You'll only lose a few ounces of coolant.