manual fan switch
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manual fan switch Hello im new to this wiring stuff but had a quick question searched a bunch of threads but couldn't get a yes or no
So what im planning on doing is installing a manual fan switch and instead of spending $70 just make one but my question is will it work and be perfecly fine if i tap into the high-speed wire which i belive is blue coming from ECM and send that wire to a switch inside and ground out the switch will it work fine or is there alot more to the process.
2000 z28 A4
So what im planning on doing is installing a manual fan switch and instead of spending $70 just make one but my question is will it work and be perfecly fine if i tap into the high-speed wire which i belive is blue coming from ECM and send that wire to a switch inside and ground out the switch will it work fine or is there alot more to the process.
2000 z28 A4
Joined: Nov 2003
Posts: 11,329
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Adding a grounding switch to the dark blue wire from the two fan relays #2 and #3 to the PCM will not turn on both fans by itself... it will only turn on the right side fan. You will also need to ground the dark green wire from fan relay #1 to the PCM to activate the left side fan. You will also have to ensure that the two sides don't get cross connected in any way. It can be done with a properly wired DPDT switch. I would also recommend including an ignition controlled relay (or perhaps a time-delay relay) in the circuit to prevent accidentally leaving the fans running and draining the battery after you shut off the car. These considerations are why the plug-and-play kits are often the best way to go.
Thread Starter
Teching In
Joined: Jun 2024
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Adding a grounding switch to the dark blue wire from the two fan relays #2 and #3 to the PCM will not turn on both fans by itself... it will only turn on the right side fan. You will also need to ground the dark green wire from fan relay #1 to the PCM to activate the left side fan. You will also have to ensure that the two sides don't get cross connected in any way. It can be done with a properly wired DPDT switch. I would also recommend including an ignition controlled relay (or perhaps a time-delay relay) in the circuit to prevent accidentally leaving the fans running and draining the battery after you shut off the car. These considerations are why the plug-and-play kits are often the best way to go.
Joined: Nov 2003
Posts: 11,329
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Yes, but the two circuits MUST be kept separate... DO NOT connect both the dark blue and the dark green wires together on a single grounding switch.
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Teching In
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Thread Starter
Teching In
Joined: Jun 2024
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tell me why before I even started the pin for the green wire was completely gone and the green wire was just sitting there doubt even working this whole time u wouldn’t happen to know the pin needed would you tried all sorts of ones I had at my house was even grinding down and nope nothing and I can’t find them
Joined: Nov 2003
Posts: 11,329
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Yes, that is the correct way to wire that type of switch. I have no idea why your green wire was disconnected. It goes from slot 42 in the blue PCM connector to slot B1 of cooling fan relay #1 in junction block #1 under the hood. The relay end should be using a standard quick connect terminal for the blade shaped relay pin.
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There’s more to it than simply grounding the blue or green wire.
http://shbox.com/1/fan_sw_diagram2.jpg
http://shbox.com/1/fan_sw_diagram2.jpg
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