Controlling rad fan w/ PDM15 and M400

[mstech]

If you are just using the output from the ECU into an input on the PDM and using it to switch the PDM output which is taken to chassis ground, then there is not an issue, what was shown in figure 1 was that the fan was supplied 12v from the PDM, and then the ground for the fan was back through the ECU, rather to the chassis. Doing this puts more current into the ECU than it is designed to sink, and most likely will lead to problems.