How do I wire the cooling fan to a switch and not fry my ECM
06-08-2008, 10:17 PM
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Drifting
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How do I wire the cooling fan to a switch and not fry my ECM
I was told by a mechanic that if I directly wire the cooling fan on a switch from the battery that it would fry my ECM because the ECM is supposed to get a return voltage of 5V not 12V. Is there a way that I can wire it in parallel so I can manually turn on my cooling fan from a switch but still have the computer turn it on at 234 F if I forget?
does the fan motor take 5V or 12V and what gauge wire should I use minimum?
does the fan motor take 5V or 12V and what gauge wire should I use minimum?
06-08-2008, 11:00 PM
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A simple way is to cut the line to the A/C pressure line NC switch and wire the manual switch in series with the A/C line switch; when you open the switch the ECM will bring on the main fan, when the switch is closed the ECM will control the main fan in normal fashion.
06-09-2008, 12:04 AM
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You had better look for a different mechanic, one that knows something, the one you have is telling you a bunch of lies. The ECM turns on the main fan by pulling the fan relay coil to ground, the other wire on the relay coil goes to 12v. When you install a manual fan switch, you connect a wire to the green/wh wire on the fan relay and your switch grounds this wire to turn on the fan. The ECM cannot be harmed by doing this and the ECM receives NO information from the fan circuit, it receives information from the temperature sender under the MAF and when it says the coolant is 228F, the ECM grounds the green/white wire on the fan relay.
