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Running a New Ground Bus

Repairs and Maintenance Blog

The DeLorean needs routine maintenance and the occasional, more significant refurbishing.  Beyond that there are also a number of customizations and upgrades to improve performance, reliability and functionality. 

Running a New Ground Bus

Joe Angell

A few years ago, while driving at night through rural Vermont in light snow, my headlights went out.  With no streetlights, all i could do was decelerate as quickly as possible and hope I stayed on the road, which luckily I did.  It turns out that all I had to do was turn off the high beams, as the low beams are on a different circuit.  But the actual problem was that my fuse box was melted, and had warped enough that the fuse had come out of its socket.

I'd replaced the fuse box, but that that doesn't fix the underlying issue of why the fuse box melted in the first place.  I soon found discussion on about installing a new ground bus, and decided to give that a go myself.  That thread is very useful, and contains a number of diagrams and pictures showing where to the grounds are and suggestions about how to run the bus.

Materials and Assembly

The ground bus will run from the headlights all the way back to the engine.  A single, continuous heavy-gauge copper wire is the best solution.

I had trouble finding 4 gauge copper wire at a reasonable price, so I decided to salvage some from jumper cables.  The trick here is to get actual copper jumper cables, not copper-coated aluminum (CCA) cables.  The best I could do there was a set of 20' cables for about $60 for a total of 40' of 4 gauge copper wire.  CCA cables are much cheaper, under $20, but aren't as good as pure copper for our purposes.

I should mention that 20' is the minimum bus length if you want to run the all the way from the headlights to the engine with a single run.  25' would give you more slack and an easier reach to the engine.  You can also get more slack just by mounting headlight end of the cable closer to the driver's side headlight than I did, which would make it easier to reach the top of the cylinder head in the engine bay.  If you need to run the the bus to the electronics behind the passenger side (I didn't, due to an EFI conversion), you'll need at least 25', or at least start running from the radiator bracket on the front frame extension instead of going all the way to the headlights.   If you want to gauge the length before buying wire, I'd suggest first buying 40' of yarn or some other thick string and running it the length of your bus run first as a kind of measuring tape.

Ideally, the bus should be a single, unbroken run, which means that you can't cut the bus wire at any point.  This lads to the question of how you connect everything else to the bus.  There are a few of ways to do this:

  • Strip the wire at the point of the junction, wrap it around a bolt, and screw it into the frame or onto a nut along with the other wires that are branching off of it.
  • Use copper wire lugs, which are pushed along the bus to the junction point, the other wires are pushed into it, and then a screw tightens clamps the wires together.
  • Use split bolts, which you place over the wire and thread a nut onto.  These are much larger than lugs, but don't require you to run the lug down the length of the wire to the junction.

I decided to go with the the lugs.  I originally bought some 4 gauge ones on Amazon, but they were too small to fit over the insulation on the jumper cables.  I later bought some 2 gauge lugs at Home Depot, which just fit over the bus insulation.

An example of a 4 gauge copper wire lug.  I wound up using 2 gauge lugs to fit over the jumper cable insulation.

An example of a split bolt.  The split slides over the wire, and the nut twists on to clamp the wire in place.

The Ends of the Bus

I also needed some ring terminals.  I got some 2 gauge copper terminals from Amazon, which fit over both the wire and insulation of the jumper cable for the ends of the bus wire itself, and some 4 gauge copper terminals for smaller wires that would attach to the same bolts as the the ends of the bus and the lugs at other parts of the wiring.

To attach the wires to the smaller terminals, I almost bought a $20 crimping tool, which works by placing the terminal in the tool and striking it with a hammer, but decided to do it the cheap way -- I stripped the wire, inserted it into the terminal, placed a nail (or a screwdriver, depending on what was handy) at the crimp point and struck it a few times with a four pound hammer.  It worked just as well, and firmly secured the the wire to the terminal. 

Crimping with a hammer and nail or screwdriver only worked for the 4 gauge copper terminals; the 2 gauge copper terminals were to thick to properly crimp this way.  In those cases I soldered the wires in.  After some quick Googling, I clamped the terminal in vice grips, wadded up some rosin-core solder, dropped it into the upright end of the terminal, and heated it with a small torch until it was melted (this only took a few seconds).  I then jammed the stripped end of the bus into the terminal and held it until the solder had hardened.  If it hardened before I could push the wire all the way in, I just heated it again with the torch and pushed it in further.  It then took a number of minutes to cool down before I could handle them again.

Afterward, I slid on heat shrink tubing to further protect the cables, shrinking it with either the torch or a heat gun.  Although I was more interested in doing this on the soldered terminals than the crimped ones, it's probably better to do it to all of them, just in case.


I decided to run the wires from front to back, starting at the headlights.  This was probably overkill; the headlights have dedicated power and ground wires, but it wouldn't hurt to add some redundancy.  Other people go as far as the radiator bracket on the front frame extension, which does save a lot of effort, most notably not having to drop the windshield washer fluid bottle.

Removing the Headlights

I had previously replaced my sealed-beam headlights with halogens, but the removal procedure should be the same for the original setup.  It's really just a matter of removing the screws that hold the covers onto the housings (four philips screws per headlight).  After a decade plus, the housings had gotten rather rusty, and the metal frame that they mount into was pretty rusty as well.

There are four components:  A cover that holds the headlight lens in place, the lens itself (which is the original sealed beam bulb or an aftermarket halogen lens assembly), the housing or bucket that the headlight sits in, and the frame that the housing is attached to.  To get to the wiring, you have to at least remove the cover and the lens.

My housings were pretty rusty, as was the frame behind them, so I decided to take out as much as I could so that I could paint it.  I removed the headlight adjustment screws (two per housing; they're long screws with a ledge on them that the housing sits on) and the spring at the corner of each housing so that I could remove the housing itself.  The idea is that you turn the screws to adjust the aim, with the spring on the corner acting as a pivot around which the headlight tilts.   With the housings out, I could paint them with POR-15.

The frame was another story.  Two of the bolts (one per frame) were behind the fascia.  I started to remove the fascia, to get at them but after breaking three bolts holding the ground effect to the bottom of the right fender, I decided I didn't really need to remove those frames, and simply painted them in place with POR-15.

Rusted headlight frame.

After applying blue painters tape to protect the fascia, I painted the rusted parts with POR-15 to project them from future corrosion.

Painting the headlight housings (buckets) with POR-15.

A better way to hold the housings while painting them -- stick them on a broom handle.  This allows much better coverage and keeps the POR-15 from sticking to the cardboard I'd originally used.

Getting the Bus to the Headlights

I started by separating the jumper cables, then cut clamps off the ends of one cable, stripped the end and crimped on a terminal. It's easier to do that before running the cable, although I only did one end to start, as the terminal's size might make it difficult to run the wire through the rest of the car.

After a bunch of fiddling, I finally decided to drop the window washer bottle.  This wound up being the right move -- the headlight harness runs through a hole in the fiberglass behind the bottle.

Dropping the Windshield Washer Bottle

To start, you need to raise the car and remove the driver's side front tire.  Actually dropping the washer bottle was another story, mostly due to all the rusted hardware around the plastic bucket that protects the bottle, tubing and wiring.  I'd had mine out a number of years ago to install headlight washers, and had already broken off many of the bolts -- in fact, only two remained.  Both were rusted to the point that the rivnuts in the fiberglass just spun when I tried to remove their bolts.  I tried to cut them out with a Dremel and a cut-off wheel, but finally just used a pry bar to pop out the entire rivnut, damaging the fiberglass slightly in the process.

To remove the bucket and the bottle, the bottle's cap has to first be unscrewed from inside the trunk.  It is then possible to wiggle and turn them both until you can finally drop them both down and out of the car.  Be aware that the tubing that runs from the bottle to the windshield wipers isn't all that long, but there's a junction that you can disconnect about a foot from bottle.

While you're in there, it's a good idea to check the connector between the headlights and the harness, and make sure everything is clean.  My pins looked brand new, which was great.

Running the Wires

With the bottle out of the way, it was easy to run the the terminated cable through the grommet the headlight harness runs through.  

There is a bundle of black wires near the passenger side headlights that provide ground to the passenger side lights, and another behind the diver's side headlights for the driver's side lights. After buying a heavy duty soldering iron from Harbor Freight (the low-wattage irons I use for fine electronics work don't provide nearly enough heat for wire as thick as this) I soldered a pair of 10 gauge black wires to each, with ring terminals on the other ends.  I used two wires to ensure that more current could be carried along this line, using the rule that doubling the wire is the equivalent of using a single wire of three gauges smaller (in this case, 7 gauge equivalent) .  These terminals and the end of the bus itself were then bolted to the stainless steel plate on the back of the fascia.

The buss attached to the headlights.  The copper terminals on the left the image are attached to the stainless steel plate behind the fascia.  The middle wire is soldered to the bus wire, which runs to the driver's side corner past the washer bottle.  The other two terminals are each crimped to a pair of wires, the other ends of which are soldered to the black wire bundles behind each pair of headlights.

Reinstalling the Windshield Washer Bottle

Reinstalling the bottle is even more of a pain than taking it out -- You'r just going to have to fiddle with it.  I found that doing the bottle and bucket together was the only way to get everything to fit.  One of the holes from the old rivnuts was just the right size to install a new M6 rivnut, but when I later tried to tighten a nut into it, it pulled through the frame.  Maybe putting a washer on when installing the rivnut would have helped reinforce it, but the bucket fits in place snuggly enough that I wound up simply using a zip tie (by drilling a small hole in the body) to ensure that it didn't get loose, and called it a day.  There was no way I was going to get to any of the other bolts without removing the fender, and that wasn't going to happen.

Reinstalling the Headlights

My headlights had been converted to halogens by DeLorean Motor Center (now DeLorean California) around 10 years ago, but my lenses had gotten scratched up over the years to that point that they looked foggy or frosted, so I decide to replace them.  I bought four Hela 4"x6" halogen lens assemblies (the specific model is "HELLA 003177862 Module 164 x 103mm Series 60/55 Watt H4 Type Single High/Low Beam Headlamp Kit") for about $50 each.  These have glass lenses and include an H4 (high plus low beam) bulb and a wiring adaptor to convert from sealed beam to halogen.  The headlight fits in the back of the lens, and the original metal cover holds the lens to the housing just as it did for the original sealed beam headlights.

For the high beam (inner) headlights, the H4 bulb still works fine, but only uses two of the pins of the existing socket (the third H4 pin just sits outside the socket).  You can get H1 bulbs if you want, but there's no real need to.

Actually getting the housings installed into the headlight frame is a bit of a pain, since the fascia is in the way a little, especially for the outer headlights.  You need to push it out of the way while inserting the adjustment screws.  To make things more complicated, I replaced my old screws with similar but not QUITE identical Chrysler import screws from NAPA to replace my old rusted.  These are slightly shorter than the original screws (not an issue), and the ledge is a little too narrow to fit the headlight housings, so I carefully used an angle grinder to widen the gap.

For the covers that hold the lenses into the housings, I replaced the old steel screws (four per cover) with new #8 x 1/2" stainless steel screws.  You may want to use steel screws, though, just so that you can use a magnetic screwdriver to guide them in, although I had decent success getting them into position with a nut starter.  I completely failed to get to get the edge-most screw in on the passenger side due to the fascia being in the way, but I'm not overly concerned about it.

After reassembling most of this, I tested my headlights and found that the driver's side outer high beam wasn't nearly as bright as the others.  After spending far too much time trying to diagnose the problem, I discovered that I had removed the halogen wiring adaptor and forgot to put it back in.  That adaptor simply swaps the high beam and low beam pins on the socket, and without that your low beam is on instead of your high beam and visa versa.

I still need to adjust the headlights, but the car needs to be on level ground for that, and I still have other unrelated work to do first.

The original headlight screw (right), a new modified headlight screw (center) and the unmodified screw (left).

Carefully modifying a new screw with an angle grinder to increase the width of gap so that it fits the DeLorean headlight housings.

The outer housing installed on the frame, both POR-15'ed.  The spring is attached at the lower right corner.  The visible adjustment screw is for the non-yet instead inner housing.  A second screw will be installed at the top of the frame.

The old fogged (due to micro-scratches) lenses (left and center) and the new Hela lens (right).  The sense also included an H4 bulb (bottom left), an adaptor pigtail (bottom center) and a rubber plug that I didn't install.

Radiator Bracket Ground

There is a ground on top of the driver's side front frame extension, where the radiator bracket attaches to the frame.  A 10mm socket removes that easily enough.  I used one of my copper lugs here: I stripped off a bit of insulation on my bus, then bolted the lug and the existing wires back onto the frame.  This was pretty straight-forward to do, especially with the tire out, but it was just deep enough under the car to make it somewhat difficult to reach with both hands.

The lug installed on the the bus wire.

The lug bolted to the front frame extension, along with the radiator bracket and the existing ground wire bundle.

Getting the Bus into the Cabin

The existing harness runs through the frame and into the cabin through roughly the center of the the fiberglass body.  This is really, really hard to get to, so I decided to just run the bus through the existing hole used by the angle drive, zip-tying it to nearby structures to keep it away from the wheels and other moving parts.  I removed the angle drive cable itself -- no matter how many times I replaced the angle drive, it would fail within 20 miles, although I could never find a bind in the cable.  I'm going to come up with another solution for the speedometer later.

I couldn't find a grommet that would fit the angle drive cable hole, so I used some leftover Dynamat to seal the hole, being careful to keep the metal backing from cutting into the wire's insulation.  This worked well and should keep road noise out as well.

Using a zip tie make sure the bucket under the washer bottle doesn't fall out, just in case.  The ground wire running to the bus is also visible here.

The bus wire running through the firewall via the angle drive cable, before applying Dynamat as a grommet.

Center Console and Arm Rest Grounds

Following the DMCTalk thread, I ran the wire above the pedals and behind the center console.  I easily found the ground bundle on the passenger side of the climate controls, and was able to use a knife and some pliers to pull the shrink-wrapped plastic cap off.  After stripping off some insulation from the bus wire with a utility knife, I ran another lug down the wire, inserted the end of the ground bundle into it, and tightened down the lock screw.

The center arm rest has a similar bundle.  I did the same thing here, with another linking the bundle to the bus.

The ground bundle next to the climate controls, now tied into the ground bus via a lug.

The armrest ground attached and ground bus attached to the copper lug.

Relay Compartment and Ground Post

I didn't see any need to do any special wiring to the relays and fuses themselves.  After snaking the bus through the center arm rest and into the relay compartment, I attached another lug to it and bolted it to the primary ground post behind the parcel shelf backboard.  This provides a direct line to the battery ground and ties all of the main grounds together. 

Since I had previously removed the old electronics from the driver's side parcel shelf area, there was no need to run the ground bus there.  The extra hardware I'd installed in that location already had its own dedicated battery ground, so it would have just been redundant.  If you have a stock setup, you'll likely want to run a ground there as well, which you could do either from the main ground post behind the passenger side parcel shelf as above, the battery itself, or by snaking the ground cable there from the relay compartment (or visa versa)


The ground bus running through a copper lug and bolted to the ground post (top left of the picture).


Engine Grounding

I had just enough bus wire left to reach the engine compartment.  I ran the wire through a hole I'd previously drilled through the rear firewall, although I could have run it through the bulkhead connectors instead.  The wire just reached the rear of the cylinder head, so I terminated the wire with a ring terminal and bolted it onto the head, through one of the mounting holes in the arm I set up for the transmission kick-down switch.

The EFI grounds were attached to the valve cover, so I put ring terminals on the end of an 8" long pair of 10 gauge wires and ran it between the end of the ground bus and the EFI grounds.

Finally, I covered the hole with some left-over Dynamat, being careful to keep the sharp metal edges away from the wire.  The gummy backing did a decent job of acting as a substitute for the grommet, and helped dampen any noise that might leak into the cabin.

A jumper running from the valve cover to the bus at the end of the cylinder head.  This is technically redundant, since the engine block is grounding the entire block, but it doesn't hurt.

The bus going through the firewall to the end of the cylinder head, then to the top of the valve cover to the same bolt securing some other ground wires.

Instrument and Radio Ground

This is at the end, because it's the last thing I did, and is the most annoying one to get to.

The instrument cluster and radio ground is apparently notoriously problematic, and is a very good one to tie into your ground bus.  It is also a massive pain to get to.  I found it based on a comment in the DMCTalk thread, and it still took me a while to locate.  In my care it was located on the main harness that runs over the pedal box, on the right side and near the top of the box, on the back of the harness.   You can barely reach it by laying on your back and looking up with your head against the corner of the center console and the gas pedal.

The real trick is that you can only reach in there with one hand.  I spent quite a lot of time cutting the plastic bundle cover with a sharp utility knife, then used a heat gun to soften the plastic before finally pulling it off with a pair of pliers.  This took me a couple of hours, with multiple breaks.

I used two foot-long pieces of 10 gauge wire, twisting the ends together and wrapping it at points with self-fusing tape to create something resembling a single wire.  I soldered one end to the bottom of a lug so that it wouldn't fall out while I attached the ground bundle to it.  Back in the car, I reached up with one hand, slid the lug onto the bundle, spun the nut down as tight as I could with my fingers, then used a power screwdriver to tighten it the rest of the way.  I could only get it so tight, as after a certain point the wires just started spinning around with the screwdriver, but it worked. 

I ran the other end of the wire behind the climate controls and into the same lug I'd used for the ground bundle.  This mostly saved me the trouble of having to run another lug down the cable.

The pair of 10 gauge wires soldered to a 2 gauge lug.

The lug and wires attached to the ground bundle underneath the dashboard.

The final installation of the lug, visible on the top right of the picture.

The 10 gauge wires now connected to the lug and ground bundle on the bus on the passenger side of the climate controls.

And that's pretty much it.  Everything seems to work fine after the upgrade.  Time will tell if it really does improve things.