Dual Fan With A/C Control

[jamies]

parallel

[Raymond_B]

Rather than running fan1 or fan2, I'd recommend running both fans in series or both fans in parallel. That way the whole core is covered all the time.

http://i61.tinypic.com/28jbp1y.jpg


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Looking at this closer.

In this scenario would all 3 relays need to be the same amp rating? Or would relays 1 and 2 be the larger relays with relay 3 being a smaller one? O only ask because at the moment I have two giant Tyco relays, so would I pick up another of the smae size or a smaller 30A Bosch style 5 pin?

[racingmini_mtl]

All 3 relays need to be able to carry the full load of one fan motor.

[Raymond_B]

All 3 relays need to be able to carry the full load of one fan motor.

Perfect, thank you!

[Raymond_B]

Alrighty, lemme see if I can wrap my small brain around the operation of this setup.

MS3X Pin 6 "Boost" activates relays 2 and 3 if temp is >X or AC is activated and fans come on at a reduced voltage. If temp is >Y pin 25 activates relay 1 and fans go to full voltage. AC operation is controlled by the MS and is working as initially proposed.

[Raymond_B]

Changed up my AC control after reading my truck's wiring diagram. AC clutch voltage runs through the low pressure switch then the high and finally to the pos side of the clutch. So that side can can supply the 12v input signal to the MS and then the MS can control AC operation via a ground switched normally closed relay . Does that make sense? I figure that it is not good for the MS to control the compressor clutch ground directly.

[Drew442]

Energizing relay 1 will do low speed. Therefore temp Y is your lower temp.

I would also have relay 1 trigger on temp OR air conditioning running. Not just temp.

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[jamies]

you really want to have all fans come on with air conditioning to keep the condensor cool otherwise your a/c pressures will get too high if it gets too hot.... this can lead to over pressure situations and stalled compressors

[Raymond_B]

Yes I wanted the process to use both AC or temp and that both the fans come on low speed. From there as temp goes up both fans will move to high speed.

Does the circuit look OK to achieve that?