2-Speed 70A Dual Fan Relay Kit – EFI Applications, Negative Trigger

Description

Specifications

Compatible with EFI Applications where the ECU has two fan activation outputs, both negatively triggered, and each must be programmable for different temperature set points!

Operation

Triggering is fully automatic (see below for specifics).

Fans come on in Low Speed via the ECU’s Fan 1 Output – which should be set to activate at 165 degF or so.  Fans shift to High Speed via the ECU’s Fan 2 Output – which should be set to activate at 185 degF or so.

Low Speed – Two fans operating in Low Speed consume less than half of the current required of a single fan operating at full speed.

High Speed – Inrush current to the fans is reduced to approximately 50% of what a pair of fans require when switching ON from a dead stop.

Triggering

• Fully automatic via low current fan outputs from EFI ECU
• Compatible with ECUs outputting a Negative (-) trigger for the fan circuits
• A/C triggering is accomplished by interfacing the A/C compressor with the ECU’s A/C input – when the A/C is turned on, the idle is raised and at least one of the fan outputs will be activated
• Optional trinary switch interface allows a single fan to run in High Speed when the A/C is turned on and the engine coolant temperature is below the Low Speed set point in the ECU.  The trinary switch must be wired to switch ground to be compatible with the negative trigger inputs of the kit.

Harness Specifics

• Wiring to Battery: Dual 10 AWG TXL, terminated with a 5/16″ eyelet
• Wiring to Fans: Dual 10 AWG TXL pairs, terminated with traditional fan connectors or Metri-Pack 630 connectors – your choice
• Harnesses dressed in Split Braided Tubing for that show car look!
• Harness Lengths:
  • Power Harness to Battery:  3ft
  • Output Harness to Fans:  3ft (Metri-Pack 630 harnesses are 1ft longer)
  • Trigger Inputs from ECU:  2ft
  • Switched Power Harness:  6ft

Performance

Maximum Current Capability: 35A per fan for a total of 70A
Typical Voltage Drop through wiring when driving a pair of 16″ fans requiring 24A continuous each with 13.8 VDC of input:

• Immediately after power up: 340mV or 2.5%
• After 30 minutes of continuous operation: 390mV or 2.8%
• After 5 hours of continuous operation:  400mV or 2.9%

Dimensions of Relay Module with mounting bracket installed: 62mm wide x 59 mm deep x 94mm to top of mounting bracket

Inrush Current Capability

Electric fans are highly inductive loads whose inrush current* can be up to four times the continuous current rating of the fan.  We have measured the inrush current capability of the included 40A fuses at approximately 105A.  This is compatible with 90% of the single winding fans  on the market, assuming a properly functioning charging system.  For fans with inrush current capability of 100A or greater (like many high quality 14″ or 16″ fans, off-road fans, etc.) as well as vehicles with charging systems outputting in excess of 14.4 VDC with the vehicle at operating temperature, we recommend that you swap the 40A fuses for our 30A MINI Circuit Breakers which have an inrush current capability approaching 600A!

*Inrush current is the current required of the fan motor when starting from a dead stop.  This is still a factor with the 2-speed kit as there may be times when the vehicle is started where the coolant temperature exceeds the threshold of the high-speed set point in the ECU, causing both fans to be turned on at full speed when the key is switched to the Run position.

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