Fan switch

[Rawze]

(05-20-2019 )earnies2 Wrote:  I remembered reading someware on here about puting a switch on the fan solenoid to manually turn it on. I recall I needed to break the ground wire to a switch...after doing some testing I noticed the ground wire dosen't loose ground when the fan kicks on but the power wire loses power? So do I put the switch on the power wire?

Some versions of MM programming default to blocking the engine fan solenoid giving an error when the ground wire is disconnected. It was done out of popular request (and as a convenience) for those who wanted to install engine fan switch on the cheap. To test to see if you have a version of MM program that has this feature, try unplugging the engine fan solenoid and see if you get a CEL in the dash. If you get no CEL light, then your good to go using that method. Otherwise, you will have to block the code in the ECU, or use a separate Solenoid for controlling the fan.

If you do have MM programming and it throws no CEL codes, then you should be able to install a switch so that it interrupts the (ground wire only) of the engine fan solenoid for switching the fan from 'automatic' (circuit closed) to 'manual' (circuit interrupted) fan on.v The solenoid ground wire is used (instead of the +12v side) so that a fuse in the circuit is not necessary.