I’m tossing some tips up in the air that I’ve come across in several forums related to the subject of adding Dash-cams, Radar Detectors, GPS unit or other semi-permanent 12 volt devices into 124 Spiders and MX-5s, and you can reach out and grab the ones that seem to fit your situation best.
There is a (hidden, capped) 12 volt accessory plug integrated with the HVAC mix unit/blower assembly in the passenger’s foot well (look just above where the passenger’s left foot would reside) that may be the easiest method for supplying power on a temporary basis (when the ignition switch is in ACC or ON mode), but for those that would rather wire in a more permanent solution, tapping into the interior fuse module in the driver’s foot well (LHD) is an ideal solution.
Turborascal has written up his process for doing just that to install his dash cam and I’m using that as a basis for this article (and some of his photos). His dash cam had a requirement for both a “hot” (always-on) 12 volt source (so that the camera can record when motion is detected while parked) and a switched 12 volt source (for normal operation while driving). So he ordered two (2) low profile mini-fuse taps (shown above) that snugly plug into the fuse slots (if they are the Lumision brand) to provide fuse-protected power. Here is the same fuse tap for a couple dollars more, because it comes with five fuses (one each – 5 amp, 7.5 amp, 10 amp, 15 amp, 20 amp). Others that have bought other brands, like Littlefuse at their local auto parts store weren’t so happy with how they fit.
By probing his fuse block with a 12 volt meter, he found the ideal fuse slots to tap into…
⇓ Remember, if you choose to tie into a circuit that is already being used (like fuse #5), you need to install two fuses into the tap, as shown (thanks psycho for the reminder)…
⇓ Turborascal chose fuse #5 for 12 volt switched power and fuse #9 for his hot 12 volt source. Please note the orientation of the fuse taps that he recommends…
He also recommends that the ideal ground connection point is behind the 10 mm bolt that secures the fuse module (note the black wire with an eyelet terminal adjacent to fuse #5).
⇓ Refiner used the tips offered in Turborascal’s article while wiring up a dash cam in his MX-5 RF, which has fewer empty fuse slots, and ended up using fuse #6 for 12 volt switched power and fuse #14 for his hot 12 volt source instead. Note that a fuse tap plugged into fuse #14 (or any of the other slots in the bottom row) needs to be oriented downwards though. He added:
I used the low-profile mini fuse taps and found it’s already very tightly fitted to the fusebox. I don’t think I need to modify the fuse taps to catch the two “fingers”.
… and later noted:
I was wrong about the fuse taps being tightly fit w/o the need of fingers. One actually came out after a few hundred miles. I fixed the problem with ½” high-density foam pressed between the fuse door and the fuse taps.
⇓ tylerwatt states that he had trouble inserting the low-profile mini fuse taps (perhaps he used a brand other than Lumision), but that regular ATM style mini fuse taps worked very well, but that you then need to stock up on a different additional series of fuses.
Other related articles…
⇓ Another source for a hot wire to tap into is the airbag message panel (the blue wire) as explained further in this article. Click photo to enlarge.
Radar Mount produces a variety of products that make use of your rear-view mirror wiring and windshield mounting bracket geared towards radar detectors.
Warhammer also did a writeup using a similar fuse tap to replace his standard rear-view mirror with an auto-dimming version which requires power. Depending on the brand and model you buy, there are different combinations of features (auto-dimming, compass, temp display, Homelink, additional map light). Here’s a link to the popular Gentex auto-dimming mirror with Homelink and built-in compass.
theemike tapped into power mirror harness for his Escort radar detector install, using the brown/black wire for switched +12VDC and the solid black wire for the ground.
⇓ naylor99 tapped into the LDWS camera wiring for his Escort radar detector install using this harness and tapping into the same color wires as theemike; brown/black wire for switched +12VDC and the solid black wire for the ground.
mirike recommends this 2 channel dashcam:
Anyone interested in a 2 channel system should have a look at the BlackSys CH-100B too. I’ve been looking for one and this is basically a slightly cheaper alternative to the BlackVue with very comparable feature set. It has a built in voltage monitor so you can hardwire it directly to fuses without the need for something like the PowerMagic Pro or other battery monitor like the BlackVue needs. It comes with the hardwire cables and regular power plug, and GPS mount so all you need are two fuse taps to install it.
For a top-end system, here is a review of a pricy Waylens dashcam available at Amazon that has the ability to tap into data from a Bluetooth device plugged into the OBDII port. The display isn’t only a video monitor as it serves many other functions such as OBD gauges ( I wonder how responsive the boost gauge is).
SargonDragon has written a nice article (with photos) for running backup camera wiring from the trunk to the CMU, that may be helpful to those installing other wiring through the rear bulkhead.