Electrical grounding question...

MadeInMaine

MadeInMaine

New member
Good morning everyone.

I just installed my BajaRack, the front legs don't actually bolt into the roof, they just sit as feet. The middle and rear legs bolt down.

My question is about grounding for lights.
I know I can ground to the rear legs because the bolts go into the body, which is a ground to the frame. BUT, am I able to ground to the front to legs that don't bolt to roof? My thought was that electricity would go from front legs, through rack (with powder coating), to rear/middle legs, and make a good ground.

Thoughts?

Cheers

Owen
 
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Just because something bolts to the roof (or anywhere else for that matter) does not automatically mean it's a good ground. It might be, but it should be checked with a meter to be sure. First the meter should be zero'd. Put it on a lowest ohms scale and touch the leads together without getting your fingers in the way. Note reading and adjust the zero adj for zero. If you do not have a zero adj then just note the value and subtract it from any measurements. A good ground should be a dead short or very close like 5 milliohms or less.

If it's not good, then either pick and measure another spot or work the spot to get better results. Cleaning and burnishing the mating areas should do the trick. Once you make your connection measure again from the bolt head.
 
If you're planning on using the rack mounting bolts as grounds then I wouldn't worry about the front foot pads.. seems like lots of people do this with successes.

Ideally you'd run a dedicated grounding lead back to the factory ground points or negative terminal of the battery, typically via the same route you use to get power up there to keep the circuit simple. What are you powering?
 
A dedicated ground lead or ground strap is ok, but should be as short as possible. Flat braided ground straps work best. You can use heat shrink along the length up to the ends if desired. To make a connection you can (using a heat sink) solder tin each end of the strap back about one inch. This will make the end stiff and easy to drill a mounting hole. Use a flat washer on the bolt. This all assumes both ends (where the strap will be connected) have been prepared and that the ground point selected has been tested and verified as a good ground point.
 
unless they plan on mounting an antenna up there, i feel like a braided ground strap is overkill for an actuator and a couple lights. are light bars that sensitive?
 
MadeInMaine said:
Light bar in the front
Small pods on the rear
And actuator on rack (Baja spy rack)
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Nice, I love that Spy rack-light. You mind as well test the rack and see how good of a ground you can get, if it's no good then move on to running a dedicated ground. If you don't want to mess around I'd just run a dedicated ground cable. Ideally they're as short as possible but being up on the roof kind of complicates that. Make sure the cable is gauged appropriately for the length and you should be ok. I look forward to seeing that system setup.
 
I would run a dedicated ground wire from the lights. You will have to scrape a little powder coat/paint off the rack to get a decent ground which could invite rust/corrosion to form and just because the ground is good through the rack at install doesn't mean it will stay good. This is something I've experienced through a ton of lighted headache rack installs on trucks.
 
[MENTION=90148]flyrv9[/MENTION]

He's not wrong about that, it wouldn't hurt to see how much resistance you're getting between your ground at the rack and the negative terminal.

Realistically though, I wouldn't be super concerned about it as it's not a sensitive component (like say a sensor that may need a very clean, low resistance ground). If you really wanted to do a more accurate comparison I'd do a voltage drop (I suggest a voltage drop since you'll see a more realistic effect of the resistance on the operation of the circuit) from the ground point on the rack (where the light grounds to) to the negative terminal (the most negative point of the circuit); if it's around or below .5v I wouldn't be concerned about running a dedicated ground as it won't suffer any ill effects from that amount of voltage drop (I realize some of you might consider .5v exessive, but consider we're talking about grounding through probably 5~10ft of material with various connections in between).
 
Kinda depends on where the ground strap is. I suggested a flat braided one (over a wire) because they hold up better to movement, wind, etc. Overkill - maybe, but a better ground = better operation.

Voltage check is fine, however I would rather know my ground is good via a resistance (bonding) check before I apply power and actually use that ground regardless of circuit sensitivity. Each to his own I guess.
 
flyrv9 said:
Kinda depends on where the ground strap is. I suggested a flat braided one (over a wire) because they hold up better to movement, wind, etc. Overkill - maybe, but a better ground = better operation.

Voltage check is fine, however I would rather know my ground is good via a resistance (bonding) check before I apply power and actually use that ground regardless of circuit sensitivity. Each to his own I guess.
Click to expand...

Not disagreeing on the resistance check, it's a good way to spot check something. But it doesn't always convey an accurate picture, granted in this case it's probably going to be fairly accurate; but it was shown/pointed out to me before earlier in my career that you can have a single human hair like strand of copper still show you perfect connection (i.e. almost no resistance). But when you actually flow electricity through that circuit it will have issues even though it looked good unloaded.

I just mentioned the voltage drop because it'd go hand and hand with the resistance check and let you know if the resistance was accurate when the circuit was loaded.
 
Last edited:
Fair enough - both are a good idea. I would do the resistance check first followed by a voltage (hot pin) check after.

I just had a problem with a tail light not working on my old Nissan PU. A voltage check revealed only 8v - not enough to light the bulb. Cause was an almost broken through wire.
 
flyrv9 said:
Fair enough - both are a good idea. I would do the resistance check first followed by a voltage (hot pin) check after.

I just had a problem with a t4ail light not working on my old Nissan PU. A voltage check revealed only 8v - not enough to light the bulb. Cause was an almost broken through wire.
Click to expand...

+1
Like discussed above, a strand of wire or conductor too thin for current passing through will read as low resistance but when loaded will cause voltage drop, or even overheat and present a fire hazard.
 
MadeInMaine said:
Thats what I think I am planning to do.

Does anyone know of a good place to ground in the back of the vehicle? would shorten the run going back towards the engine.

Cheers
Click to expand...

Once the negative wire is inside the vehicle really there are a lot of options under the plastic paneling. I would probably route it down to the jack compartment and at least try to make it somewhat accessible in case there was a problem or you need to remove the wiring asap. Scrape the paint, nut and bolt it, and put a little dielectric grease over it and you should never have to worry about corrosion.
 
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