Fuse Box Repair
My red 1988 Testarossa had developed a fault in the air conditioning system as described in another repair section. Having located and repaired a potentially serious issue inside the fuse panel, I thought it may be wise to have a look at the fuse panel on my blue 88 car as a side to the work being done on the engine.

There had been a previous water leak from the base of the windscreen and I discovered water had been entering the fuse panel due in part to this problem. As the car wasn't running and the electrical system had been isolated, I liberally sprayed a water displacement agent (WD40) around the fuse panel and left it whilst other work was being done.

First step in this process is to remove the spare wheel and empty the front wheel well area completely to allow easy access to the fuse panel. I'm about 187cm tall and not too slim, but was able to sit in the well quite comfortably whilst working. Certainly beats leaning over the car and straining your back. The little wooden chock seen in the image below is the safeguard against the wind slamming the hood on your head. It's a bit of 100 x 35 pine and sits just under one of the hinge pin bolts. Ferrari service tool #37651!

Climbing into the blue car, I turned the pins and dropped down the fuse panel cover. Assisted by a small flat blade screwdriver, I pulled out all of the long white plugs that push into the fuse panel. Three on the left, one on the right, and two banks of two laying through the centre. Looking at the 4 plugs running along the bottom of the fuse panel, the top left one has a pair of brown wires going into it. These are the second wires from the right side of the plug. These two wires supply ignition feed of +12v to the air conditioning controls. This was the only burnt plug on the red car, so I pulled this one first on the blue car. Surprise, surprise, the same pin was burnt and damaged here also.

Knowing that the repair of this damage required removal of the fuse panel, I went ahead and pulled the rest of the plugs. Here is what I found!

Not only the plug with the AC wires, but four other plugs with serious damage and one with some signs of previous repair. Although no evidence of burning, someone has replaced two of the plug pins with 4.8mm female blade crimp connectors.

With so much plug damage, it was obvious that the panel would have to come out. This is a very simple procedure, requiring removal of only two small Phillips head bolts (with washers) holding tabs along the top of the fuse panel. To ensure that I put the plugs back into the right places, I took a digital image to help with the re-installation. You can just see one of the top tabs that holds the panel in place.

With all of the plugs removed, including the large black one with the red cable, and the two top bolts removed, the entire panel will tilt forward and lift out of the car.

Now it's time to get serious. Grab the panel and your tools and climb out. You are done sitting in the wheel well for a few hours now!

First step in stripping down the fuse panel is to remove all of the relays. Be careful! They are not all the same. I cleared sufficient space on my bench to lay them out in the same configuration as when they are mounted in the board. And took a few photos to remind me in case I knocked them. They all have Bosch part numbers for ease of identification.

Once the relays are out, flip the panel over and remove the small screws from the back. Get a fine blade screwdriver under the panel cover, lift it out and store away. You can now see the rear of the printed circuit board.

As can be seen in the above image, there are a number of badly burnt pins on the board, naturally corresponding with the burnt plugs in the images above. Some were showing signs of extreme heat and burning, others only slight solder and pin discoloration from excess heat.

There are 16 screws with white nylon cup washers that hold the board in place. Remove these screws and the board will come free of the frame. All of the fuses and the fuse blocks will come clear with the board.

Remove the fuses and lay them out in order of removal, then using a very fine flat blade screwdriver, very gently prise the fuse holder from the pins. This leaves you with the board and pins complete ready for repair.

The circuit board is made up of five individual layers interlaced with the relay mount blades, connector pins and fuse holder blades. In the picture above and on the lower left corner, you can see a heat affected pin with a burn hole alongside it. This hole went through three layers of the board and three sections of track were in contact which would have caused serious problems to components in the car if left alone.

All of the other burnt areas had serious track damage, penetrating through various layers, and some had even burnt the legs off the pins. I had a bunch of pictures of damaged Testarossa's sourced from 'Wrecked Exotics' website. Looking through them there were twice as many front fires as rear (engine) fires, and having located real problems in both of my cars, I now have a pretty clear understanding of why these cars could catch fire up front!

Repair of the damaged tracks is a bit daunting, and probably not for your home handyman, but anyone with good soldering skills and a lot of patience will be able to manage it. Each layer must be removed individually. It will be quite obvious which components are attached to the first layer, directly to the copper tracks. With soldering iron and solder vacuum pump in hand, remove all of the relay, fuse and plug pins that are attached to the first layer.

Once this is done, very gently peel away the first layer and remove to a clear bench area. Again using the solder vacuum pump and some soldering wick, clean up the holes on the layer and remove any / all excess solder from around the pin holes.

The amount of layers to be removed depends entirely on the damage present. There was very little damage on the board of my red car, just some excess heat marks were visible. This was simply cleaned up and then a solid bridge wire soldered in to place. (Images later) of this procedure.

Unfortunately the blue car had sustained extensive damage, requiring the removal of all five layers of the board. After some hours of quite tedious work I ended up with quite a pile of fittings which had been removed from the board to allow removal of the various layers.

Once all of the required layers were separated I laid them all out for inspection and cleaning. Although extensive, most of the damage was contained to small areas and only three areas had sustained quite bad lifting of the copper tracks. A soft brass bristle brush about the size of a toothbrush was used to clean up most of the areas. Where the tracks had lifted I bent them back gently, taking great care not to crimp bend them, and cleaned under the track with a razor blade. I then used 'Loctite' cyanoacrylate adhesive with primer to bond the track back down to the board. Below you can see the boards all removed and cleaned up ready for repair.

To ensure that exposed tracks never come into contact with the tracks on the next layer, it is vital to cover them with some form of tape. DO NOT use common electrical tape for this purpose. It is not designed to be heat resistant and may actually ignite! I located a teflon based tape which was quite thick and perfect for the job. I tested it with a heat gun and it was very durable and impervious to heat. The teflon tape was adhered using an industrial double sided tape which was also not acetic and very thin. Be careful not to use anything conductive as it will be in contact with +12v of live feed. If in doubt, consult with the guys at your local electronics store. Just use the tape in the areas of damage as can be seen below. Make sure that you chase through any small holes that need to line up with the following layers or you won't be able to get the pins all back in properly. I mounted a 1/16" drill bit into the cordless and ran through every pin hole to make insertion of the fittings nice and easy. The pictures below show the tape fitted to reinforce and repair the board. Once applied, turn the board over and mark the areas or the tape to be drilled or removed to allow the other layers to be fitted. You can see the damage done to the board quite clearly. Next step is to repair the other layers, chase out all of the holes and then start the arduous job of cleaning up all of the removed pins and fittings ready for the rebuild.

Stay tuned!!

Updated January 9th 2007.


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