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Hello there.... I have e 2019 Ascent and am attempting to tap the rear view mirror for a switched 12 volt power supply for an escort radar detector. I have checked the plug that leads into the mirror. I have found a constant on power wire with a meter but not a switched power wire.

Is there a switched 12 volt source at the plug? Thank you....

Tim.....
 

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You simply run wires from the mirror under the headliner lip to the left A-pillar. You can pull off the A-pillar's cover (be cautious of the airbag), and then run the wire down under the dash into the fuse panel. Use a fuse tap and plug it into fuse socket #7 for a switched 12 VDC source.
6167
 

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^^^ totally. This is what I did for a dash cam. I also used a fuse tap on #7. Note that the right side of the fuses is the battery side for all the fuses so the tap needs to be installed with the wire coming out to the left as in the pic above. I mounted the small dash cam right below the rear view mirror attachment to the windshield and routed the wire under (above) the front lip of the head liner and down the behind left side A pillar cover, routing the wire behind the air bag. The pillar cover just pulls off but is restrained by a couple of straps.

It is important to note that Subaru "prohibits" mounting anything on the windshield or on the dash in front of or below the EyeSight cameras. The prohibited zones are depicted on page 9 of the EyeSight Quick Guide. I presume the concern is something, or reflections in the windshield in front of the cameras, interfering with EyeSight operation.

A number of forum participants have mounted dash cams as I have and haven't experience problems with the EyeSight system, but that's not proof that something couldn't go wrong in all situations.
 

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This is great. I was looking for a fuse for my radar detector direct wiring.
thanks!!!
 

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There's power right at the mirror. Lower the sunglass holder all the way. 2 bolts back behind it, remove. The light assembly will come down and you can tap power there. No need to run all the way back to the fuse panel and potentially interfere with the air bag. I do not know if there's switched power, I use fixed constant 12 volts because my dash cam and corresponding rear view dash cam are on 24/7 for security. (When vehicle isn't moving, they draw almost no power. When motion sensed the display will come on)
 

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There's power right at the mirror. Lower the sunglass holder all the way. 2 bolts back behind it, remove. The light assembly will come down and you can tap power there. No need to run all the way back to the fuse panel and potentially interfere with the air bag. I do not know if there's switched power, I use fixed constant 12 volts because my dash cam and corresponding rear view dash cam are on 24/7 for security. (When vehicle isn't moving, they draw almost no power. When motion sensed the display will come on)
This is not recommended. Electrical Engineering 101. Whenever you add any new load to an existing circuit you have the potential of overloading the existing wiring and its fuse. The fuses are very specific values and the wiring is a specific gauge for very good reasons.

For example, if you added a device that draws 2 amps to a circuit rated for 5 amps and is already drawing 4 amps, you may overload the ampacity (amperage capacity) of the wiring. The wiring's ampacity is protected by the fuse which is carefully rated to protect the wiring. While the battery and alternator can easily handle the extra current, the wiring on any given circuit may not. Fuses primarily protect the wiring, not just the electronics themselves. All wiring has a specific gauge or thickness and thus can only handle so much electrical current. This maximum ampacity is protected by the fuse. Without the proper fuse, the wiring could melt and possibly catch fire if overloaded.

Take a look under the dash and notice the tiny wires used. Subaru very specifically selected the gauge of those wires to both reduce overall weight (for better gas mileage) and costs (copper is expensive). They weren't careless about it, their engineers knew exactly from calculations and measurements precisely how much maximum current each circuit would draw and then precisely selected the appropriate wire gauge. Then they precisely selected the correct fuse to protect the wiring of each and every circuit. That's why there are so many different fuse ratings in the fuse box. It's certainly not random.

If you go haphazardly adding additional loads to this existing wiring, you're now taking the risk of throwing off this delicate balance. Sure, you may get away with it, but you'll never know how close you really are overloading the wiring and blowing the fuse unless you know how to recalculate the circuit's total potential current load given all possible factors, which few people do. Some people even think that if the fuse blows it's ok to simply add a larger one to compensate for the extra load. Wrong, now you're allowing the possibility of exceeding the ampacity of the wiring and risk melting it or even starting a fire. If you damage the wiring due to incorrectly adding a non-Subaru approved device, replacing a wiring harness could be very difficult and expensive and it won't be covered by the warranty.

The only proper way to add a new load is to run separate, appropriately sized wiring directly to the fuse box (or battery) and then add a separate appropriately sized fuse to protect the new wiring. Fuse taps were designed to do this. They allow you to tap into the fuse box's power while retaining the existing circuit's correct fuse and also adding a new fuse for the added device. You even have to be careful doing this, if you were to add say a powerful audio amplifier, you may overload the feed wiring for the fuse box itself and need to run a heavy gauge wire directly to the battery itself.

The bottom line is that you need to understand at least the basics of electrical circuits and wiring before messing with any vehicle wiring. It has to be done correctly. I haven't even mentioned the potential for disturbing very sensitive ECU electrical communication systems such as the Can-Bus.

Modern vehicle wiring is nothing to be complacent about, especially these days when manufacturers select very small gauge wire to reduce weight and costs. Long gone are the days where manufacturers routinely ran heavy gauge wiring. Now, vehicle wiring is only as thick as it absolutely needs to be and there's little room for error.
 

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This is not recommended. Electrical Engineering 101. Whenever you add any new load to an existing circuit you have the potential of overloading the existing wiring and its fuse. The fuses are very specific values and the wiring is a specific gauge for very good reasons.

For example, if you added a device that draws 2 amps to a circuit rated for 5 amps and is already drawing 4 amps, you may overload the ampacity (amperage capacity) of the wiring. The wiring's ampacity is protected by the fuse which is carefully rated to protect the wiring. While the battery and alternator can easily handle the extra current, the wiring on any given circuit may not. Fuses primarily protect the wiring, not just the electronics themselves. All wiring has a specific gauge or thickness and thus can only handle so much electrical current. This maximum ampacity is protected by the fuse. Without the proper fuse, the wiring could melt and possibly catch fire if overloaded.

Take a look under the dash and notice the tiny wires used. Subaru very specifically selected the gauge of those wires to both reduce overall weight (for better gas mileage) and costs (copper is expensive). They weren't careless about it, their engineers knew exactly from calculations and measurements precisely how much maximum current each circuit would draw and then precisely selected the appropriate wire gauge. Then they precisely selected the correct fuse to protect the wiring of each and every circuit. That's why there are so many different fuse ratings in the fuse box. It's certainly not random.

If you go haphazardly adding additional loads to this existing wiring, you're now taking the risk of throwing off this delicate balance. Sure, you may get away with it, but you'll never know how close you really are overloading the wiring and blowing the fuse unless you know how to recalculate the circuit's total potential current load given all possible factors, which few people do. Some people even think that if the fuse blows it's ok to simply add a larger one to compensate for the extra load. Wrong, now you're allowing the possibility of exceeding the ampacity of the wiring and risk melting it or even starting a fire. If you damage the wiring due to incorrectly adding a non-Subaru approved device, replacing a wiring harness could be very difficult and expensive and it won't be covered by the warranty.

The only proper way to add a new load is to run separate, appropriately sized wiring directly to the fuse box (or battery) and then add a separate appropriately sized fuse to protect the new wiring. Fuse taps were designed to do this. They allow you to tap into the fuse box's power while retaining the existing circuit's correct fuse and also adding a new fuse for the added device. You even have to be careful doing this, if you were to add say a powerful audio amplifier, you may overload the feed wiring for the fuse box itself and need to run a heavy gauge wire directly to the battery itself.

The bottom line is that you need to understand at least the basics of electrical circuits and wiring before messing with any vehicle wiring. It has to be done correctly. I haven't even mentioned the potential for disturbing very sensitive ECU electrical communication systems such as the Can-Bus.

Modern vehicle wiring is nothing to be complacent about, especially these days when manufacturers select very small gauge wire to reduce weight and costs. Long gone are the days where manufacturers routinely ran heavy gauge wiring. Now, vehicle wiring is only as thick as it absolutely needs to be and there's little room for error.
Wow! You said a mouthful.
I replaced my incandescent bulbs for LED bulbs. The current difference more than offsets the draw from the camera. Besides, it's already installed and already working fine, so there is that...

Routing a wire down to the fuse box to tap a fuse at that point does nothing to prevent the same issues you described. The wire feeding the fuse panel is sized too you know. Adding a splitter to share that fuse holder with a second fuse does load the primary side of that source.

I can tell you there is a serious risk of injury running wires down behind the plastic on the the roof post where the air bag is. Route the wire wrong there and it can interfere with the air bag deployment if it's in front or wrapped around it. I started to route mine that way and felt darn lucky I didn't trip that thing just pulling the cover off.
 

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Wow! You said a mouthful.
I replaced my incandescent bulbs for LED bulbs. The current difference more than offsets the draw from the camera. Besides, it's already installed and already working fine, so there is that...

Routing a wire down to the fuse box to tap a fuse at that point does nothing to prevent the same issues you described. The wire feeding the fuse panel is sized too you know. Adding a splitter to share that fuse holder with a second fuse does load the primary side of that source.

I can tell you there is a serious risk of injury running wires down behind the plastic on the the roof post where the air bag is. Route the wire wrong there and it can interfere with the air bag deployment if it's in front or wrapped around it. I started to route mine that way and felt darn lucky I didn't trip that thing just pulling the cover off.
I have no issue with anyone installing their own aftermarket devices and deciding what's safe for their own vehicle as long as they know what they're doing. However, I do have an issue with anyone broadly recommending this to other people who may not be able to determine this for themselves when the method described is not electrically sound or generally regarded as safe.

If you need to add additional minor electrical loads, then running separate wires to the fuse box is by far the safest way to go. I did mention the possibility of overloading the fuse box, but that's not likely unless you're running very high current devices such as a powerful audio amp, as I described. The primary wiring and bus feeding the fuse box can handle several more ordinary minor load devices and was specifically designed to do so because Subaru knows people are going to be adding dashcams, radar detectors, and other such devices. So, they sized it appropriately. Adding a few low current fuse taps was expected and is safe enough. It's certainly much safer than breaking into an existing, balanced secondary circuit as I'm certain you know.

The airbags are very carefully designed not to go off unless directly and deliberately triggered. It's highly unlikely that could happen merely by removing the A-pillar's cover. It's also highly unlikely that anyone could damage any other aspect of the system merely by removing the cover and routing a wire. The cover was carefully designed to be safely removed and there is plenty of room to safely route a wire behind or well around the airbag. Subaru knows both owners and service technicians might be doing that. It's not much different than removing any cover for servicing, and it's very hard to believe anyone would be dumb enough to wrap a wire around or otherwise interfere with the airbag, but I will grant you that remote possibility, lol. No one can possibly account for all the possibilities, but you have to assume people are not that dumb.

Ideally, people should not be messing with any component of a vehicle without knowing all of the implications, but there is a best and safest way to do it if necessary. Breaking into and adding additional loads to balanced existing secondary circuits is not considered safe, adding minor loads to the fuse box is generally regarded as safe if done correctly.

Whenever anyone modifies their vehicle, they are taking a risk. If the risk is carefully calculated and the work is done correctly, it can be safely mitigated given the correct methodology. If anyone has any doubts as to their abilities or the recommended methodology, then have it done professionally.
 

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Welp, I will be running a new line to the fuse box.
it’s just a radar detector, so the load is very low, if I recall, it was around 1 amp.
#7 is described elsewhere as a good spot: it’s empty, and 12v switch, which is perfect. We’ll test it first though with the volt meter.
The wire has a grounding wire, and has its own fuse too, it’s a smartcord from Escort.
parts arriving this week, I can let you onow how it turns out.
@pro10is agreed about responsible alterations (we have some good qualifications albeit not automotive)
I think it’s the responsibility of a person to know their limits :)
 

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Got the radar direct wired in!
i bought the Escort smart wire, started at the header and tucked the wire above the eyesight along the top to the pillar. No need to even pull it off. Tucked it into the seam to traverse the top pillar and then tucked it behind the black molding until it reached the bottom of the lower panel and brought it into the fuse box from below.
used the spot #7 which is switched 12V.
checked with the volt meter first. Then checked the wire tap, added 7.5A fuses to both slots, and crimped and connected (clipped off the connector on the direct wire) the escort wire to the fuse tap. Again, tested all out with the volt meter. Then ran the button under the steering wheel to the right side of the driver bay attached with velcro. Now at my easy reach. Also used the mirror mount, which ironically placed the radar detector buttons now in good reach. Maybe would have skipped the smart button had I notes that first.
All in all surprised I did not need to pull any trim. Works great. Shuts off with the car.
Autodimming side mirrors arrive next week!
 
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