Blade Fuse Kit Frequently Asked Questions & Troubleshooting Tips

Where can I find installation instructions and videos?

On our website here:

Installation Guides:

Installation Videos:

After installing the kit on an E28, Fuse 5 keeps blowing when I unlock or lock my doors. Why?

Blade fuses react faster than torpedo fuses and thus are more sensitive to situations where a circuit is pulling current near the limit.

The electric door lock actuators on classic BMWs will pull more than 8A (the original torpedo fuse spec) briefly, which can cause the 7.5A blade fuse to blow. This can be exacerbated if an aftermarket remote lock/unlock system has been installed.

Holy Grail Labs takes a conservative approach in the fuses we provide with our kits. The 7.5A blade-fuses we include for Fuse 5 on our E28 kit does not blow regularly for many customers, The electrical engineering math, however, shows that an 10A fuse is perfectly acceptable and we recommend customers that have trouble with Fuse 5 blowing, simply use a 10A blade fuse.

See this thread for a deeper discussion: Fuse #5 fighting with the central locking system - MyE28.com

For more general information on how blade fuses behave differently than torpedo fuses, see this web page: Torpedo Fuses: The Bane of Classic German Automobiles.

After installing the kit on an E28, Fuse 2, 3, 7, or 8 keep blowing when I turn on my head lights. Why?

More than likely, you are running more modern headlight or high-beam bulbs than were originally specified by BMW. These bulbs are drawing slightly more current than the originals. Blade fuses react faster than torpedo fuses and thus are more sensitive to situations where a circuit is pulling current near the limit.

Holy Grail Labs takes a conservative approach in the fuses we provide with our kits. The 7.5A blade-fuses we include for the headlight circuits, Fuse 2 (right low beam), 3 (left low beam), 7 (USA right high beam), and 8 (USA left high beam) on our E28 kit do not blow regularly for many customers. The electrical engineering math, however, shows that an 10A fuse is perfectly acceptable and we recommend customers that have trouble with the headlight fuses blowing, simply use a 10A blade fuse.

Many E28 owners who wish to run higher output headlights install an intermediate relay system to ensure the stock wiring can handle the increased current. If your car blows 10A headlight/highbeam fuses we highly recommend you install such a relay system. 

For more general information on how blade fuses behave differently than torpedo fuses, see this web page: Torpedo Fuses: The Bane of Classic German Automobiles.

Where can I find more details on which E28 fuse circuit does what?

See this thread on mye28.com: US vs Euro differences in electrical wiring / system and fuse boxes, which includes a link to a spreadsheet detailing everything.

Or just view the spreadsheet here: E28 Fuse Box Wiring Spreadsheet. 

What brand fuses do you use? Where can I purchase replacements?

We ship Littelfuse brand fuses with our kits. We source them from both Mouser and Digikey, but they are available from other retailers such as Amazon as well.

I have more questions about your products. How do I get them answered?

Email us at support@holygraillabs.com! 

Or, if you'd like to help the community by sharing your questions (and our answers) please post your question on the my28.com forum thread here: Blade Fuse Retrofit Kits - MyE28.com