Had an interesting experience recently I thought I would share.

I lost illumination of the interior lights in my 1994 Discovery 1. I checked the relevant fuse via my multimeter and it conducted with the familiar "beep" associated with a low resistance connection.
In attempting to track down the problem I applied a volt meter across each set of bulb contacts in the light fixtures. Each positive contact read 12 volts and grounds were good, however bulbs would not illuminate. I placed the bulbs across a separate 12v source (old car battery) and they each lit up...

After some head scratching I decided to pull the fuse and noticed the thermal wire strand was incompletely broken. There was a slight whisker of metal still remaining. After some research it seems this is not completely uncommon, but the issue is that a multimeter will apply a very low load to the fuse which will generate a 12 volts, but under load the resistance of the wire whisker will restrict current flow to the item being powered.

This is actually the second time I have observed this phenomena in the Discovery (maybe my fuses are not well made).

This is a problem because my "go to" method for electrical issues used to be running the voltmeter across all of the fuses first just to make sure they are intact by listening to the audible beep. Now I think I might start paying attention to the resistance reading themselves and look for small increases vs. the other fuses. Also might just have to visually inspect them if I'm out of other ideas...

 

Thanks for that info. I’ve never heard of that but it’s a good piece of info to keep in the back pocket.