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71 Datsun Restomod

PDM Installation & Configuration

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Discussion and questions related to the course PDM Installation & Configuration

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Watched the PDM course but I am still completely lost on a very basic question. I have a Haltech 2500 paired with a Wiring Specialties chassis harness, engine harness and PDM 15.

With something like the Datsun Combo switch for Headlights, turn signals and Wiper function. Does the power into those switches come from the PdM or do I still need some small fuse panel to supply the input power to those??

Same with the blower motor. I have a very very small wire labeled “blower” which has to be for the blower switch and not the motor. Obviously the motor is going to have to get power from somewhere with a larger wire but it’s not on this harness. I have just been under the assumption that the PDM gets rid of ALL fuses and relays.

Complete novice with PDM so im sure I sound like an idiot! Should I just run a Firewall bulkhead post to get power to these old school switches and blower motor and wire in the correct outputs to the PDM?

Every bit of the OEM wiring is off this car except pigtails from the steering column switches.

First, you have to understand the OEM wiring. Then you can decide the best way to approach replacing fuses and relays with the PDM. Generally inputs to the relays (switches) would be inputs to the PDM. They would normally need to be setup to ground when they are active, the OEM may have these switching to battery voltage. Most PDM's will have the capability of providing a pull-up resistor to the switch inputs, and you just connect the switch between the signal and ground (which may have been power in the OEM wiring).

You configure the PDM to use those switches to turn on the outputs for things like blowers, turn indicator lights, hi and low beam headlights.

Wipers are often a special case and may require special circuits in the PDM to be used. This is because they often have a high-speed power, and a low-speed power. Whenever you apply the high-speed power, the low-speed power is 'back fed' and produces a voltage -- the PDM needs to deal with this. Also you often have a "park switch" which is used to turn off the wipers when they are in the park position, you may need to use this as an input.

Ok, sounds like I jumped the gun by thinking I didn’t need ANY of the OEM wiring.

After reading this 5 times I think I understand what you are saying now. I will give it a try. Thanks for responding!

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