Erratic Fan - 1994 Mazda MX-5 Miata Long-Term Road Test

1994 Mazda MX-5 Miata Long-Term Road Test

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1994 Mazda MX-5 Miata: Erratic Fan

August 02, 2010

1994 miata fan relay.jpg

The other week I noticed that Project Miata's radiator fan was cycling on and off erratically. Opened the hood. I put a finger on the fan relay. It was clicking over indecisively as if possessed -- so the fan was doing what it was being told, but it was being told wrong.

There isn't much to the cooling circuit. The ECU commands the fan relay based on advice from a coolant thermosensor.

Of those three components, the relay is the most likely to crap out. I theorized that the sporadic clicking is the relay in its death throes, and that soon it wouldn't function at all. If/when that happens then the fan won't run and engine go boom.

Short of time and feeling frisky, I ordered a new relay and popped it into the fuse box this morning. At five bucks, the stakes were low. Went for a quick spin and... no difference. Time to find my multimeter.

Jason Kavanagh, Engineering Editor @ 178,xxx miles.

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