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Old 11-10-2022, 05:04 PM
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glovebox flashlight charger is switched-power, or you can use a timer

I needed a switched power source for the aftermarket fan I installed, replacing the mechanical fan that broke, but struggled to find any underhood, but finally did inside...from another thread:
Quote:
Originally Posted by working on it
After searching for "switched power" for hours on this forum, I repeatedly saw conflicting statements about what is and isn't a safe "switched power" circuit to tap into (I didn't want to run afoul of any modules). So I decided to look for the uninstalled flashlight charging circuit in the glovebox (it was mentioned a couple of times by trusted sources).

There was a black plastic rectangle where the flashlight would've been, so I used a screwdriver and popped it out. Voila', there was the two-prong receptacle, with a brown ground and a black/red? positive (lighting was bad). After testing with my meter, to verify it was switched, I made that circuit my trigger-power source...

Now, the key controls the power to trigger the fan in two modes: 1) automatically via the T-switch on the radiator, or 2) manually, via the hidden switch under the dash. However, once the key is turned off, the fan quits (I had wanted it to run another 16 minutes, until sleep mode started). I guess the flashlight circuit sleeps instantly. Good enough for one day's troubleshooting...I'll look for a sleepy circuit at another time.
The flashlight charging port was great, though I had to feed the wiring behind and under the console along the firewall (I used a 2-foot section of PEX pipe to snake the wires thru). As I was unsure of how my fan would perform, in two situations:
  • 1) by not shutting off the fan when the key was on (but before the fan could fully cool the radiator, to avoid heat retention, during short shopping hops in the summer) using the switched power, or
  • 2) if the thermostatic switch might draw the battery down below 12v, if I switched the power feed back to "always on power" (the underhood battery posts),
I added a timer to the circuit that would limit the battery drain, so there'd be plenty left to start the truck.
Name:  Blackvue.JPG
Views: 125
Size:  75.2 KB Power Magic Pro BlackVue Vehicle Battery Discharge Prevention for Parking Mode


also from another thread
Quote:
Originally Posted by working on it
the device works, shutting off the fan either at the 12.5 vdc cut-off point I set (I thought 12.0 vdc was too low) and at a maximum time of 6 hours (it won't run that long, ever). It'll shut off earlier, if the thermal switch says to stop. I might adjust the thermal switch to shut off a bit lower, if need be.
I tested the device by leaving the key on, fan still running, and it shut it off after awhile, before the specified minimum battery voltage was reached. I never tried leaving it on to the specified time limit, as the themostatic switch shut the fan down long before then (and, I could've then switched the power circuit entirely to the always-on power, but never did, but perhaps in the future I will).
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