Mark VIII Fan - w/ Spal Contr. Help!

I tried that same controller and fan combo with probs. It would start up then kick off. After talking to spal tech support I found out its not rated above 30amps and the Lincoln fan far exceeds that so it cuts off, some kind of over load protection.

SPAL controllers use PWM, which switches the voltage on and off many times a second to achieve a variable fan speed according to the engine temp. The hotter the engine gets, the more duty cycle the SPAL controller provides, making the fan run faster. Using an external relay with a SPAL controller will disable this nice feature. You will have two fan speeds: Full blast and off. You will also loose the easy start and current limiting features of the SPAL controller. In simple terms, don't attempt to use a relay with a SPAL controller.

The best fan controller available today is a DC Control unit. Now serving. Cost is about $110. Be prepared to wait 4 weeks or more to receive your controller once you have sent in your payment. The controllers are custom made in small lots and lead times can stretch out.

Simple on/off fan controllers are the Hayden or Imperial controllers available through Advance Discount Auto Parts and AutoZone. The non adjustable one is about $30 ( Hayden 226206) and the adjustable one is about $60 (Hayden 226204). I recommend you do a Google search on Hayden and the part number for more info.

The controller should ramp up to 100% DC for half a second. For a large-draw fan, this might be enough to trip the internal breaker.