Volvo fan relay
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On The Tree
Joined: Sep 2015
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Volvo fan relay Volvo fan relay and dual Ford Windstar fans. I wired the relay as follows from the picture below going left to right, the high speed to the bigger fan (2) and the low speed (1) to the smaller fan (grounded both fans) then the PCM wired with the blue/green wires coming out of the Speartech harness to the middle of the Volvo fan relay with the high and low speed wires. And of course the 12 volt wire from the fan relay to 12 volts.
Problem is, if I hook up both green and blue wires from PCM to the 2/1 wires in the middle of the Volvo relay it kicks off the big fan and only runs the smaller fan. If I just plug one in (the bigger of the two fans it runs like it should (temperature wise). I am trying to tie in a Trinary switch, and just can figure out why when both the blue/green wires from PCM are hooked up it won't run the bigger fan, then if needed the smaller one as the PCM saw the temperature getting to high
What is wrong with the way I have it wired? the pic below is not how mine is wired just using it to show for reference as the numbers on the relay itself above how I wired mine.
Problem is, if I hook up both green and blue wires from PCM to the 2/1 wires in the middle of the Volvo relay it kicks off the big fan and only runs the smaller fan. If I just plug one in (the bigger of the two fans it runs like it should (temperature wise). I am trying to tie in a Trinary switch, and just can figure out why when both the blue/green wires from PCM are hooked up it won't run the bigger fan, then if needed the smaller one as the PCM saw the temperature getting to high
What is wrong with the way I have it wired? the pic below is not how mine is wired just using it to show for reference as the numbers on the relay itself above how I wired mine.
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Joined: Jul 2019
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this is from a 1998 v90 schematic, so your mileage may vary....
that said, it may take a minute to wrap your head around the schematic, but the fan control relay is specifically designed to NOT run the low speed and high speed fan output at the same time. So the behavior you're describing makes 100% sense.
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one more thing i figured i would mention, i determined through empirical testing with an oscilloscope that the volvo fan control relay does not have the same level of coil suppression that a typical relay does. Depending on how the low side switches on the LS ecu are protected, it may be okay, but i would recommend adding external suppression (read: diodes)
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