I’ve found a few of grounds in my car either not connected, not existing or just plain sketchy. I’ve seen some threads on grounding but I’m looking for more exact photos to compare my mess with others.

 

My batteries negative terminal leads here. The black and yellow wire. It’s connecting to the bracket that holds the engine fuse box. That doesn’t seem right to me as the bracket is only held to the body by two 10m bolts. The ground also seems to continue to somewhere else but I didn’t trace it because it was getting late.

 

I’m adding an amplifier for my speakers and I want to make sure my wiring is good. Another thing I noticed is that my headlights seem to get brighter when I give the car gas. I’ve only noticed at idle. But I think I may need to run some additional wires like the “big 3” upgrade. I cannot test my alternator right now because the fuel tank is dropped but I don’t think it’s the alt. I’ve been told it can be bad grounds as well as a poor connection from the alt to the battery.

 

First off, you have some sort of parts store battery terminals. Those things suck. It's a pain but you want some sort of proper crimped on battery terminals. The ones that have a cover that bolts on and holds the wire on make a poor connection and it gets worse with time.

Stock the negative battery cable runs from the terminal to that in-line connection that bolts to the fuse box bracket then it goes to a bracket that bolts to the power steering/AC bracket. Mazda could have done better there.

Dale

 

My small relay box is directly off the terminal it screws onto the positive terminal. I’m not sure how i would use a crimp on with that.

 

Sorry, for the negative terminal. For the positive you can get a new bolt-on terminal that's OEM for under $10, it's a Nissan part, search around on the forum on that.

You can also get the whole positive terminal/fuse box assembly for like $70 or so new. New positive terminal, red rubber boot, fuse box with all the fuses and the cover, just bolt the wires up to it.

Dale

 

I was planning to get new terminals so I’ll look into these. I think I want to thread and screw my ground into the body directly instead of back into that frame, but I’ll I think I’ll bridge the new ground to the old one. Any ideas? I think I’m also going to do a “big 3” not to thick a wire but enough to help the alt charge.

 

Yeah that's not a bad idea. Many people for years (myself included) have run a ground from the battery terminal to an unused 10mm hole on the driver shock tower, that was one of the early 3000 RPM hesitation fixes.

Dale

 

An additional ground? Or do you just replace the factory one?

 

Additional ground. Pettit Racing still throws in a free ground wire with purchase. This was a VERY common "mod" back in the day. Just run another wire from the negative terminal to a chassis ground.

I don't know how necessary it would be if the ground wire was done better than stock, though. Really there is already a chassis ground but it just goes to that goofy bracket.

Dale

 

I have my ground wire from them, but also I need to rewire my main ground because it’s two wires crimped together covered in a electrical tape mess from previous owners. I don’t know what the original guage wire was from battery to chassis. But maybe I should run the main ground to the unused spot you mentioned and the ground from petit to the bracket?

 

one of these little taped screws?

 

There's a hole in the front part of the strut tower that most use. I don't know if those taped up holes are just holes or are threaded.

The hole that most use is super obvious and in the open.

Dale

 

I’ll take a look but also when you suggested a crimped ground terminal. Did you mean one like this? I’m not sure how I would add a second ground to something like this. Also I got the new positive terminal you suggested and it fits very nice. Way better than the weirdness they had going on to make the old one fit.

 

The black/yellow wire is the original battery-to-chassis ground wire, it also continues from that mounting bracket to the engine. My calipers measured 7.5mm for the outer diameter (including the insulation) and about 6.4mm for the copper. For comparison, some 2AWG battery cable from ProwireUSA measured about 7.4mm copper (I didn't measure the insulation). Search online for "(your city) auto electric" and you might find get lucky. I recently found a local supply place that has all sorts of nice wire and terminals, I didn't need them to build cables but that's a common part of RV backup power installs so I suspect they could do a good job.


Also, the Air Separation Tank in your photo looks like it's ready to be replaced. I deleted/bypassed my AST years ago, but others have said that discolored plastic (from original black like the Intercooler end tanks, to brown like your photo, then green or yellow) is a sign that they are one step closer to splitting and leaking.

 

That thin wire being what went to the battery terminal doesn’t seem right to me. I’ve never seen such a thin ground on a car. I’m hoping to run two-three new grounds to the battery terminal. One being the stock ground, the second being an additional battery to chassis and the third being alternator to battery ground. I also have a Pettit engine ground upgrade kit. Also I’ll be picking up the Pettit swirl tank soon. Seems their out atm.

 

OK, let's break this down.

First off, I'm not a fan of cheap parts store stuff. This is a Japanese supercar, not an '85 Camaro.

Here is a nice, OEM-style, negative battery terminal that will have proper metric fasteners on it -


Here's a hammer crimper -


You put the ring terminal on the wire, put the terminal in the crimper, and hit it with a hammer. It will make a very solid crimp.

Then get some decent crimp-on terminals. These are decent for 4-gauge wire, don't know what gauge you want to run, but this gives you an idea -


So, new negative terminal on battery. Cable with crimped ends bolted to terminal going to ground point on strut tower. Another cable with crimped ends going from that point to the engine block.

Did a similar setup on a friend's FD and it's been rock solid.

Any battery terminal that has screw-on or set screw type mechanisms to hold the wire in place won't work. It's not tight enough and you're going to get corrosion in that joint over time and you'll be right back where you are now.

I would probably go the extra step and use adhesive heat shrink on the crimped terminals, that will look good, protect the terminal, and keep anything out of that joint.

Dale

 

Thank you Dale, I completely agree. I want OEM, style and quality. I was actually thinking of getting a second of this terminal you showed me for the ground, since it’s what I used for my positive. I also found the screw spot you were talking about.

 

The positive and negative terminals are slightly different sizes on a car battery, you have to make sure you get the appropriate terminal. I think the negative is slightly smaller.

Dale

 

That’s true the negative is smaller, but I think it’s pretty negletable. I’m pretty sure the terminal you linked is the exact I ordered for my positive and it fits perfect.

 

There were all sorts of measures taken to minimize weight and/or cost on the FD, the thin ground wire has worked pretty well compared to other aspects of these cars. With a stock engine and stock-size battery and stock wiring, my 1994 car cranks over just fine in 2021. I agree with stepping up the wire gauge especially if you're planning a relocated battery, additional fuel pumps, additional fans, aftermarket stereo, etc.