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*gmachinz* · 03-10-2014, 08:07 PM

The Spal PWM units work for lower amperage, less CFM pulling fans. They were never designed to manage the high current demands longterm of a lot of the OEM fans, including the Mark VIII. The first PWM had a limit of 35A sustained with a peak of 50A internally so you would think it would be a quality enough unit to still run a NEW Mark VIII with an average high speed draw of 28-32 amps.

And while I never had any issues with it, Spal changed the design to include an "overlimit" current so you couldn't run a high inrush current fan-otherwise it'd shut the controller down. That's when I gave up on Spal and decided to build my own relay setup.

The dual 16" Motorcraft fans measure 19"x34"x6.5" its a super stout fan assembly! The only harnesses I have that I would even consider is either my resistor 3-speed harness or a single speed, 100A relay harness which I use a unique relay incorporating dual resistors and dual series diodes.

03-10-2014, 08:07 PM	#22
gmachinz Account Suspended Join Date: Jun 2011 Location: Des Moines, IA. Posts: 4,143	Re: F/S: 73-87 power window relay harness The Spal PWM units work for lower amperage, less CFM pulling fans. They were never designed to manage the high current demands longterm of a lot of the OEM fans, including the Mark VIII. The first PWM had a limit of 35A sustained with a peak of 50A internally so you would think it would be a quality enough unit to still run a NEW Mark VIII with an average high speed draw of 28-32 amps. And while I never had any issues with it, Spal changed the design to include an "overlimit" current so you couldn't run a high inrush current fan-otherwise it'd shut the controller down. That's when I gave up on Spal and decided to build my own relay setup. The dual 16" Motorcraft fans measure 19"x34"x6.5" its a super stout fan assembly! The only harnesses I have that I would even consider is either my resistor 3-speed harness or a single speed, 100A relay harness which I use a unique relay incorporating dual resistors and dual series diodes.