Locating ground on fuse block
 

I'm ready to wire my GPS unit into the fuse block using a fuse tap on an existing ACC switch. It's pretty obvious that I will plug in the hot (red) to the tap but where do I put the ground? Is there a way I can test this with my DMM? The block has all the hot wires from the factory harness plugged in on the left and right sides. The top of the block has multiple available plugs and appears only three or four are used. The bottom of the block has only two prongs, larger than the ones on top.

If it's of any help, the boat is a 99 Baja 272. I wanted to use the fuse tap so I can tie in to an existing ACC switch. In this case, the switch I'm tapping into controls the factory depth meter. I've used the DMM to determine which ACC switch is routed to which fuse, so as long as someone can tell me how to test for ground (possibly the available plugs on the top of the block?), I'm good.

You can test for ground. Just put one lead (red) on what you think is hot & the other (back) on ground. With your meter set to v-dc. If you get a 12v reading you've gotten a ground & a hot. If you don't get a read, tap the hot on the dist block & tap a ground off the gauge panel or one of the switches.

On my Cig, i think they have all the grounds ran to a common bus bar, it then runs back to a engine block. I would think Baja does it similiar. Did you check behind the gauge panel or some sort of dash access panel?

under the helm there should be a drop out for the VHF radio (if equipped). Open that, and look up and to the right, there will be the fuse block. At the very TOP of the fuse block, there is ground bar, it should have a few open studs on it, and also a few open spade connectors if you use that style.

If for some reason you do not have the dropout for the VHF radio, remove the gauge cluster by removing all the surround screws and look down and to the right, you will see the block from there.

For easiest access for wiring, remove both so you can run one are one way, and one arm the other.

Hope this helps.

Also, are you installing a GPS Speedo gauge, or an actual GPS unit? If installing a GPS speedo, there should already be a ground at your current speedo, even though it works off water pressure, you still use the ground for the illumination. If you are installing a regular GPS, ground to the grounding bar on the fuse block.

Also, your accessory switches are already hot (Acc 1, Acc 2, Acc 3) at the end of your switch panel if you have them, they are prewired. Just run a wire from the switch to the GPS, then the accessory switch you use for the GPS will turn it on and off, do not tap at the fuse. I am not sure the pin # on the switch that sends power out, but if your looking at the back of it with all the spade connectors, it will be the bottom one on the left side. (With the switch being held vertically)

Why don't you just tap into the ground on that same switch?

Jason - Thanks for the tip, poked around everywhere and it seems the entire thing is hot.

B - Boat seems to only have one access panel at the helm, and when opened, I can see the gauge cluster wires but couldn't find another common bus area/bar.

Smurf - VHF not equipped, I'm attempting to install a Garmin GPS unit with just the basic red/black connections. The accessory switches are all on the right side of the helm behind the throttle; no access to them. Currently switch is for factory depth meter. You mention don't tap at the fuse but isn't that what a fuse tap is for? I'm trying to avoid splicing into the factory wiring/harness so I figured a fuse tap with a very small fuse on it should work fine.

Irish - I cannot find the ground coming off the switch due to the location of the ACC switch.

Hopefully this crappy picture from tonight helps. I tested polarity/voltage using DMM and the leads touching the fuses. Seems as though the entire thing is hot. Not seen in the photo is the top portion, which has a bunch of available spades(?) but I'm not convinced those are grounded.

http://i791.photobucket.com/albums/y...ajafusebox.jpg

There should be ground bus somewhere, if not, ground it back to a battery.

At the very top of that block will be 2 posts. One will be hot & the other will be ground.

At the top of your pic on the right looks like a small ground bus bar with 2 black wires going to it. That should be it.

At the very top of the picture, there is black wires going to the top bar on the fuse block. This is the common ground. To access your accessory switches on next to the throttle, remove the screws that hold the entire panel in, and you will be looking at the back of all the switches.