Dual fan setup - will this work?
Thread Starter
On The Tree
Joined: May 2004
Posts: 161
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From: London, UK
Dual fan setup - will this work? The LS1 PCM has two signals coming out of it, high speed fan (RED 33) and low speed fan (BLU 42). On the original car I believe they have a dual speed fan, but I have two individual ones. I would like to rig the fans up as the attached diagram explains (how do I insert inline attachments?)
If my electronics is correct, this should only turn on the right hand fan when the low signal is active (as the diode stops the high speed relay operating), but the high speed signal should operate both relays and hence both fans.
I know this is a simplistic diagram, but if it will work, what kind/rating of diode should I use (I know nothing about diodes except that they work a bit like a one way valve).
If my electronics is correct, this should only turn on the right hand fan when the low signal is active (as the diode stops the high speed relay operating), but the high speed signal should operate both relays and hence both fans.
I know this is a simplistic diagram, but if it will work, what kind/rating of diode should I use (I know nothing about diodes except that they work a bit like a one way valve).
Launching!
Joined: Aug 2003
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From: Down along the strand in NJ
Yes that should work..
The diode needs to have a VOLTAGE rating more than 16volts(gen output) and a CURRENT rating higher than the current rating of the fan.
The initial current draw of the fan is going to be higher than the steady draw.....better yet get a 0.1uf Capacitor and place it accross the diode.
The diode needs to have a VOLTAGE rating more than 16volts(gen output) and a CURRENT rating higher than the current rating of the fan.
The initial current draw of the fan is going to be higher than the steady draw.....better yet get a 0.1uf Capacitor and place it accross the diode.
Thread Starter
On The Tree
Joined: May 2004
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From: London, UK
Have been told on another site that both the high and low speed signals will be operating in the high temperature situation, so the diode is not needed - I can just wire one signal to each relay... is it true that the PCM uses switched earth?
Launching!
Joined: Aug 2003
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From: Down along the strand in NJ
Don't understand that?
If indeed they are for different speeds on the same fan, then having both on at the same time does not make sense(medium speed?just kidding), this would creat a problem inside the fan itself, and it would probably not run.More likely it would burn up.
Are you sure it was not intended for two fans to begin with?
If indeed they are for different speeds on the same fan, then having both on at the same time does not make sense(medium speed?just kidding), this would creat a problem inside the fan itself, and it would probably not run.More likely it would burn up.
Are you sure it was not intended for two fans to begin with?
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Joined: Nov 2001
Posts: 1,707
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From: Anderson, Indiana
You have the polarity backwards and you need to lose the diode. The PCM switches the LOW side of the relays, not the high. Put the "+" where the ground is, and the GROUND where the "+" is, erase the diode, and it will work.
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91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
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On The Tree
Joined: May 2004
Posts: 161
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From: London, UK
So the PCM is switched earth as someone had told me. On the original car, the low setting put one fan on and the high setting put two fans on, is that correct?
I should have got you to modify my loom... it looks like my engine has exploded!!
I should have got you to modify my loom... it looks like my engine has exploded!!
