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Where can I tap in for ACC ignition power?

Mighty Burger

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Recently I've been having some issues with starting the truck. It's gotten to the point where this morning I wasn't able to start it up at all. The battery died. After quickly checking I noticed there is a significant parasitic draw of 60mA. It's only become a major problem now because of how cold it's gotten. Thankfully electronics is the one area I'm good at and I was able to nail the problem down to the aftermarket radio someone did a terrible job installing. Think stripping wires, twisting them in a pigtail (no crimp, no solder) and covering the mess in packing tape. I'm going to have to clean up this mess. Without the radio the parasitic draw drops to 3mA.

This radio (as well as most other radios out there) have two different positive wires going into them: one that is permanently connected to battery power, and one that is only supposed to be powered on when the key is in the ignition and set to ACC or ON. Well, whoever installed the radio hooked both of the wires to the permanent power source, meaning it stays on even when the key is taken out. I need to find somewhere to connect the radio's ACC wire to so it doesn't draw a bunch of current while the truck's off. Where can I go to tap into this ACC power source that turns on only when the key is in the ignition?

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Well, fuse number 7 (from the left side of the box) is the accy fuse for the radio (and the cigar lighter) so look at the wires that would normally go to the radio for a Brown one. This will be the switched source for power.


The other continuous source is to keep the memory presets and the internal clock going when the ignition is shut off.

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No because there was no clock and the station presets were push button. The Brown wire is from the accessory fuse and shuts off with the ignition key... which is what you asked for. If it was cut and just hanging around it may have grounded and blown the fuse but it should be there on the harness.

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Finished the job! The radio now shuts off when I take the keys out and there's no parasitic draw anymore. Here's what I did in case anyone else needs to do this in the future.

The old stuff was sketchy and I'm surprised none of the wires came loose, or that the packing tape never fell off and let the exposed metal short out. I capped off each unused wire stem and redid every connection with a proper solder joint and heat-shrink tubing. If anyone else is doing this crimp connections should work fine (provided you do them properly) I just had solder equipment and was more used to soldering. I prefer heat-shrink to electrical tape because it's cleaner and doesn't fall off over time but honestly anything is better than packing tape...


I had to look around for a while under a disgustingly dirty dashboard and after some hunting I found what seems to be the wiring harness and connector that was plugged into the old radio. Someone used blue painter's tape to keep it way up there out of the way. There were multiple wires going into this connector, one of them being brown. Just to confirm I set my multimeter in continuity mode, poked one end into the fusebox at fuse #7 and the other into the connector where the brown wire came in. Sure enough, it beeped soon as I put my keys in and turned it to ACC. So I cut into that brown wire and ran wire down to the radio, of course properly capping everything off to prevent shorts. Also no fuses were blown thankfully.


Thanks for the help everyone!

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