LED Funk Fuses

[Witsend]

Just a heads up that there are some aftermarket fuses out there that have a little LED that is supposed to light up after the fuse blows but don't if the load is unplugged or the ground side switch for the circuit load is off.
On a clean 2001 Caddilac STS (from Arizona, with No Green Death connectors) with Evap code p0440, I Tried 3 different scanners to activate the evap vent valve Starting with my newest scanner and ending with my oldest MT2500. No click heard. I tested voltage at the red wire to the vent valve and it measured 10 volts so I just assumed I was running the battery flat and hooked up my battery maintainer . Now I try 2 different Noid lights with the unplugged harness connector of the Evap vent valve and neither light. I take my Power Probe and with the MT2500 turn the circuit on and I see with the power probe it shows good green light and noise for ground switching but red power supply wire still shows 10 Volts and unable to light a noid light. I look at the circuit and it's a straight shot to the rear fuse box under the driver rear seat. I test all fuses and replace a couple bad fuses and the one for power to the Evap Vent valve which had a little led light built into it that lights when if fuse is blown as long as the load side of the circuit has a path to ground which it doesn't until the PCM commands the normally open vent valve closed. I saw it momentarily light testing the fuses with my power probe.
Measuring 10 volts at the Vent valve connector you assume the fuse is still good and had me checking connectors for green death or harness for rodent damage. You aren't doing anyone any favors by installing these LED Funk Fuses. Any body that owns a Cadillac STS that replaces the nice big heavy stock rectangular battery with vents tube hookups with a much smaller lighter Optima battery of half the length with top posts sticking way up just below the rear seating is suspect of being weak of mind and body. At least the power seat and power tilt telescopic steering column works now with the second blown fuse changed out. I did replace the Evap vent valve with a cheap Duralast one that has a nice loud satisfying clank like putting a ball peen to the fender

[Crusty]

You've just proven that there is still a place for the venerable, fundamental, TEST LIGHT.
Even with a run down battery, showing 10 volts, if the circuit was intact, it would still light a test light.
GM has Kent-Moore part numbers for their tools, even test lights.
The ones specified are of particular current flow designs. They have amperage and milli-amp specs.
I have at least 5 different test lights, and could easily manufacture many more rube-Goldberg test lights.
All of my purchased test lights have been tested and measured for their current flow. I then marked on them their milliamp measured values with permanent ink markers.
To make up your own, with a vast array of current flows, and wattage ratings, all you need is a bulb SPEC GUIDE from bulb manufacturers such as G.E, Sylvania, Wagner, etc.
In those SPEC GUIDES they specify the voltage and the wattage for every bulb they sell.
In essence, it's a way to voltage drop test the circuit with a KNOWN load.

Your point regarding the visual notification fuses (led) is a good one.
Just because there is "something" at the end of the circuit doesn't mean it's "good".