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Is there a customer access or another circuit I could tap for power only when the engine is running? I am reconsidering doing E-fans and electric water pump. I can turn the pump on and power the fan switch with the key-on, but I would rather them be off until the engine is running.
If this is a gas application, you could tap into the fuel pump circuit. It would run for 3 seconds or so when the key is turned on, but then turn back off until the engine is started. I would suggest using a relay as not to load the fuel pump circuit.
Maybe tap into the 4 AUX Upfitter Switch circuit. Tap into a wire coming out of the under steering wheel fuse block but before a switch. Basically tap into the power wire before it goes into a switch.
Should be an open customer fuse in the fuse box under the dash. You can check with a circuit light to find the correct one. I am using this for my after market fog and driving lights so I don't forget to turn them off when truck is off.
Priority one is to not have the efans and epump active on ACCY, and I would prefer them to be off until after start up. I just don't want my start and elec accessories fighting for juice. That's why I would like a circuit that would either drop off during start up or just not activate until after the starter has done it's deed.
Shutting off when the starter is engaged is easy. Just go up to the ignition switch and test some of the heavy wires, you will find at least one that will only work with the key on and will go off when the starter engages. Run this wire to trigger your relay and your set.