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Fuse Box Replacement

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. 

Fuse Box Replacement

Joe Angell

My fuse box has seen better days.  Three of the fuses had melted so badly that I had to replace the sockets with inline fuse holders.  While waiting to get some money together for the EFI conversion, I finally took the time to replace my fuse box with a new one from Houston that I'd gotten a few months ago.  I actually wound up buying two of them -- my dog decided the first one would make a good chew toy.  At least this gave me extra terminals for the inevitable mistakes I would make.

In principle, a fuse box replacement isn't that hard: 

  • Remove the passenger seat for easier access.
  • Lift the parcel shelf carpet and remove the fuse and relay access cover.  
  • Remove the relay sockets to get more slack in the wires.
  • Lift the fuse box as high as you can.
  • Label all the pairs of wires going into the fuse box. 
  • Cut the wires as close to the fuse box as you can. 
  • Strip and crimp new terminals onto each wire, with heat shrink tubing if desired. 
  • Solder the wires to the terminals, if desired. 
  • Insert the terminals into the new fuse box.
  • Put new fuses in the fuse box.
  • Put back the relay sockets and the relays.

In practice, you have to deal with the somewhat cramped space and wires that are just long enough (and sometimes not).  All told, it took me about ten hours to replace the fuse box.

Resources

I found a few handy posts on DMCTalk regarding fuse box installations:

Searching Google and YouTube provides a lot of examples of how to properly crimp open-barrel connectors and how to diagnose bad crimps. 

 

A ratcheting open barrel crimp tool (left). wire cutters (top) and wire strippers (bottom).

Proper Tools

Besides the standard tools like socket wrenches, screwdrivers, pliers and wire cutters, you'll also need some other more specific tools to do this properly:

  • Wire cutters:  While you can use the wire cutters on a simple wire stripper, they usually have the blade well behind the strip area, which can make it difficult to cut wires in a cramped space.  I used dedicated wire cutters to make things easier.
  • Wire strippers: You can use simpler pliers-like strippers, but I decided to invest in a high-quality squeeze-handle stripper in the 10-20 gauge range that both cuts the insulation and removes it with a single squeeze of the handles.
  • Ratcheting Open Barrel Crimp Tool:   Open barrel connectors require a crimper with a "w" shaped receiver.  This curls the connector "wings" around the wire and the insulation, ensuring a tight, secure connection.  I had a nice crimp tool already, but it was only suitable for closed barrel connectors.  I decided to replace it with a new tool with replaceable dies. A ratcheting tool ensures that you have used enough pressure to completely crimp the connectors, as it will not release until they are fully crimped.

Getting Started

The first thing to do is remove the passenger seat from the car.  You don't have to do this, but it makes things a lot easier to access.  Simply jack up the car, hold it up with some jack stands, remove the four nylock nuts holding the seat to the floor, and lift the seat out of the car.  One of my studs was stripped, and I had to cut the nut with a Dremel to relieve enough pressure to take it off.

With seat out of the way, you should disconnect the battery behind the passenger seat.  You can then remove the parcel shelf carpet and the relay and fuse area access cover.

Removing the Old Fuse Box

To remove the old fuse box, you need to cut the wires as close to the terminals as you can.  This can be tricky, as the wires to the fuse box are pretty much the exact length they need to be to get to the fuse box.  You can get more slack by unscrewing the relay sockets from the wall of the compartment.  In my case, there was one small bolt-headed screw holding each strip to the compartment.

With the relays out of the way, you should have a fair bit more slack -- enough to tilt the fuse box up and cut the wires off, at least.  The fuse box is clipped into place, and a firm tug will snap it free.  Once released, I found I had the best access by tipping the back of the box upward, and leaning over the box to access the wires. 

Before cutting any wires, you'll want to label them.  Since I can barely read my own handwriting, I did this using a label printer.  I write the fuse number and the description on each pair or trio of wires.  It doesn't matter which wire is on the left or right side of the fuse (although if two wires go into the same side, you do need to keep them together); you just need to make sure you remember which wires go to which fuse.

I would label a pair of wires, then cut them as flush to the fuse box as I could, then move on to the next pair.  This worked pretty well and I had the fuse box out fairly quickly.  The only problem I encountered was that the labels didn't stick to the wires too well, so I bent them into hooks to keep the wires from slipping through.

Crimping New Terminals

With the old fuse box out of the way, I could now crimp new terminals onto the wires.  It was easy enough to figure out how to use my new wires strippers, but the crimp tool took me a bit to figure out.  The trick is that the open side of the terminal lines up with the "w" shape in the crimp tool.  The re are two sets of "wings" on the terminal: the outer pair hold the insulation and act as a strain relief, while the inner set hold the bare wire itself.  When the crimp tool is squeezed closed, the "w" bends the "wings" inward to lock the wire and insulation in place.

I didn't use heat-shrink tubing, but if you decide to you should obviously slide it on before crimping any terminals.   I didn't see the need for it because the terminals fit completely in the fuse box, and there is no bare metal to be a risk.

The Houston kit includes a few extra terminals, but I made enough mistakes that the second kit I had to purchase after my dog chewed up the first fuse box came in quite handy, although I imagine you can pick up more terminals at auto parts stores easily enough.   In a couple of cases I didn't push the wire far enough into the terminal and only crimped the end of the wire but not the insulation.  In some other cases, I'd pushed it in too far and crimped only insulation.  At least twice I didn't realize that I'd caught an already-crimped terminal or wire into the end of the tool's jaws as I tried to crimp another terminal, thus crushing the first terminal and requiring me to cut the wire and do it over again.

Be sure to tug on each wire to make sure it is securely attached to the terminal.  Make sure the wings are completely crimped against the wire and insulation.  I had to go back and tighten a few after I realized that I should have used the second, mid-sized position on my tool instead of the third, larger-sized position.  

Crimping was by far the longest part of the process.  The trick is managing to get the crimp tool on the connector, get the wire in the right place, and then crimp it all down, all while fighting the limited space in which you have to work.  I eventually used a utility knife to cut some of the electrical tape holding the wiring looms together so that I could untangle some wires and get more slack to work with.

After crimping, you can solder the terminals for extra strength.  I did this after all my terminals were crimped, making sure that the solder flowed into the wire strands.

Connecting the Fuse Box

With the terminals crimped, the next step is to mount them in the fuse box.  This is easy enough -- simply push them in until they snap into place.  I found a pair of pliers helpful to hold the wires and push them in with more force than I could with my fingers.  Make sure you put the right wires into the right holes; I screwed up early on and spent fifteen minutes removing the then-mangled connector from the block, although I luckily managed to avoid damaging the block itself too badly.  Another time a wire came off a terminal, and I had to remove it from the block and crimp and solder a new one on.

As you put each terminal in the box, tug each to ensure that it really is in there all the way.  You don't want to put a fuse in and have the terminal push out of the block instead of holding the fuse. 

Finishing Up

With the terminals connected to the new fuse box, you can now install new fuses and re-mount the relay sockets and relays.  If all went well, you should be able to turn the key and run through all the systems making sure that everything is working properly. 

Parts

  • Fuse Box Assembly, which includes the fuse box, fuses and terminals
  • Heat Shrinking Tubing (optional) 
  • Solder (optional) 

Tools

  •  Wire Cutters
  • Wire Strippers, 10-20 gauge
  •  Ratcheting Open Barrel Crimp Tool
  • Socket/screwdriver to remove the relay sockets
  • Socket/wrench to disconnect the battery
  • Socket to remove the nylocks holding the seats in the car
  • Label Printer, or masking tape and a sharpie, to label the wires
  • Soldering Iron, if you decide to solder. 
  • Heat Gun or similar to shrink heat shrink tubing, if you decide to go that route