Low and High Speed Fan + Together???

[AnthonyR23]

Hey so I am wiring this spal controller, it is a mark 8 fan, with the spal controller it just has one fan positive, can I hook both the low and high speed positive to this fan positive?

Thanks

 

[jrichker]

No.

The SPAL controller will use only the high speed connection. It does Pulse Width Modulation (PWM) which makes the fan operate at a variable speed according to how hot the engine coolant is.

Do not connect the low speed fan wire to anything. Cover it with heat shrink tubing and ty-wrap it out of the way.

 

[AnthonyR23]

cool thanks jricher!!

 

[jrichker]

Some explanation of what PWM is and how it works would be helpful. Both the SPAL and DC Control fan controllers use PWM to vary the fan speed according to engine coolant temperature.

Any fan controller that uses a relay to directly control the main fan cannot use PWM. The relay will not switch on and off quickly enough to make PWM work correctly.

Some units may use a relay to turn on the auxiliary fan used for the A/C condenser or some purpose other than controlling the main fan.

 

[HISSIN50]

Joe, I think you're going to confuse people with the comment about the relay. As you well-know, some of the PWM controllers use a relay for an external/ancillary trigger.

You and I know the difference, but someone is going to see instructions with a relay in the schematic and think the controller isn't at all PWM'd.

 

[jrichker]

Joe, I think you're going to confuse people with the comment about the relay. As you well-know, some of the PWM controllers use a relay for an external/ancillary trigger.

You and I know the difference, but someone is going to see instructions with a relay in the schematic and think the controller isn't at all PWM'd.

Input noted and corrections made. Thanks for catching my oversight.