I’ve had 3 different customers with an X100/X308 variants come in with potential alternator issues within the past 6 weeks. I always start by the visual inspection of the alternator, starter, bulkhead connector on the P/S, mega fuses in trunk and battery. I didn’t mention checking the heel board connectors because I’ve never seen one loose or corroded before. It’s becoming increasingly common that the mega fuses in the trunk are getting loose and causing concern for a fire. Vibration, added electrical load and deteriorating braided battery cables are most of the issues related with the mega fuses burning up due to added resistance. Years ago I had a car get towed in because there was no power from anywhere when turning the key on. The issue I found was a bolt on the backside of the mega fuse holder got so hot that it melted out of place and grounded against the spare tire well that it was bolted to and charred the metal in that area. I’ve seen blankets, shop towels and other flammables around the spare tire before and a risk of fire was always great. I *highly recommend* taking a 10mm, 13mm wrench and 20 minutes of your time to disconnect your battery, removing all cables at the mega fuse holder (take a picture with your phone of the cable orientation) that’s located to the left of the battery just ahead of the spare tire. There’s 2 10mm nuts that hold the mega fuse holder to the body. Once that’s off, take the 2 mega fuses out, gently but firmly tighten the 13mm nuts that holds the bolts to the fuse holder. If the fuses themselves are not charred, you can take a fine grit sandpaper or wire brush to clean any corrosion off. After you reinstall the fuses, gently but firmly tighten the nuts that hold them inside the holder. Reinstall the fuse holder in the trunk and battery cables.

 

It’s subtle but, the top left bolt is discolored compared to the others after I flipped it over.

 

This sounds like a Sticky

 

Great info thanks.

I assume the 500 amp is the starter circuit & the 175amp is the rest of the car's connections?

 

That’s correct on both counts Hooli.

 

Here we can clearly see what resistance does in high electrical current contacts.

 

I agree, Highhorse. Great posts, Addicted!

I have added this thread to the XJ8 / XJR "HOW TO" quick links thread under this title:

High Power Protection Module / Fusebox Protection Module - Melting, Shorts, Risk of Fire

Cheers,

Don

 

Addicted, are you back at Sach’s? LMK, may need some work done(getting lazy in my old age&#128514

 

Yes but, we’re always inundated with newer complicated crap and a few project cars that can’t get touched.

 

I forget how I ended up with these but I found an old box of NIB 175 amp megafuses for the S-Type?
They are about 20 years old.

Someday I'll clean out my shop and be amazed at how much junk I have accumulated.

 

Nice find Bob. It’s like a treasure hunt isn’t it?

 

I do have 'rabbit-trails' into some areas of the shop.