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homemade87 · 10-31-2018, 12:51 PM

The best and easiest way is a tech2 to cycle them . The wires to the pcm for fan 1 and 2 are green and blue in the relay fan harness . These wire are a ground trigger . Grounding these requires taking things apart .

The fans are a single speed fan . The low speed puts both fans in parallel , basically running each fan on 6v for 1/2 speed . The 3 relay system will switch to 12v to each fan ( high speed ) or parallel for low speed 6v . Depends what the pcm is calling for .

It sounds like your system is working just fine . I do not have the factory temp setting but I do know it is somewhere around 220 on and 195 off for low speed . I would think the high speed would be somewhere about 235 on and 225 off . If this is close this is the reason you are not seeing your high fan come on . Your system is working in the perimeters of the low speed settings.

10-31-2018, 12:51 PM	#10
homemade87 Registered User Join Date: Apr 2010 Location: Guntersville Alabama Posts: 1,073	Re: 2006 cooling fans The best and easiest way is a tech2 to cycle them . The wires to the pcm for fan 1 and 2 are green and blue in the relay fan harness . These wire are a ground trigger . Grounding these requires taking things apart . The fans are a single speed fan . The low speed puts both fans in parallel , basically running each fan on 6v for 1/2 speed . The 3 relay system will switch to 12v to each fan ( high speed ) or parallel for low speed 6v . Depends what the pcm is calling for . It sounds like your system is working just fine . I do not have the factory temp setting but I do know it is somewhere around 220 on and 195 off for low speed . I would think the high speed would be somewhere about 235 on and 225 off . If this is close this is the reason you are not seeing your high fan come on . Your system is working in the perimeters of the low speed settings.