Tech Area

Radiator Fan Test

Question: I am working on getting the fan switch and conector on a 86 se v6 auto ac car.. I noticed at the car wash that the fan isn't running any more with the ac on. I am getting power some times through the plug. I am wanting to test the fan before getting a new fan motor and relay.

Answer: Not at all sure what you are asking, but below are a few thoughts.

1st, hope you are not pressure washing under the hood. There are far too many electrical relays, motors and switches that though waterproofed, are not designed to take on direct water pressure.

2nd, you didn't say how you knew that power was sometimes at the plug (assume you mean fan motor connection). If by a voltmeter or 12v test lamp showing interruptions, not by the fan sometimes working, then the power interruption would be before the fan connection. Relay, wiring/connections, a/c controller or if engine is hot, the engine fan switch.

3rd, a quick "field test" of the fan motor is to spin the fan blades. They should spin easily (without any scrapping sound against the shroud) and for a fairly long time, without "shuddering" to a stop. Shuddering would indicate very worn brushes and/or armature in the fan motor.

You could also power the motor directly from the battery or other 12v source, letting it come to a stop at least once to check for the shudder, intermittently applying power to make sure it always speeds up.

The engine fan switch is the single wire sensor between the t-stat housing and the forward (seat side) valve cover pointing straight up out of the intake manifold. It is known for failure. It is a ground for the circuit and can be checked (when engine is hot) and with ignition on, by just grounding the wire. If the fan motor was not running, and then begins to, the switch is bad. This method can also be used to check the a/c controller. Engine cold, ignition on, controller a/c button(s) pushed on, ground the wire and the fan should run.

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