Sorry, one DVOM probe on the left high beam purple wire. The other probe on the right high beam purple wire.

00.3 Reading

Then either one of the purple wires to battery negative. Need resistance for both tests, 200 ohm scale. They will be different readings.

No reading at all.

Both of those readings are good. Not sure what time it is by you, but it's bedtime here, (11:15pm) ;) I'll come up with more tests tomorrow and post them. Do the auto lamps work properly? (come on when it's dark) Does the flash to pass and dimmer switches work properly? (pull the turn signal switch lever toward you). BTW, there IS a grounding relay in the circuit. We'll get into that later. No joy in testing that thing :(

It's 10:19PM here (Dallas, TX)

Do the auto lamps work properly?
YES

Does the flash to pass and dimmer switches work properly?
YES

Does the flash to pass and dimmer switches work properly?
YES

I've been trying to find that grounding relay but can't find it. We'll pick back up tomorrow. Thank you for your time.

I have access to pretty much any vehicle schematic online.
If you need anything else let me know.

https://blazerforum.com/forum/attach...ine=1384961763

Thanks Burned, huge help!

Hypedave, not exactly sure where the grounding relay is on your 2000. My guess is under the hood. The relay plugs into a block that looks similar to a fuse block, with relays only. There should be at least one other relay plugged in, (the park lamp relay). Turn the park lamps on and off and follow the click;) The grounding relay has 4 terminals: 2 light green with black trace wires on one terminal, 1 yellow wire, 1 black wire. The 4th terminal connects internally, (inside the relay block). You probably won't be able to see the wires though.

Next step: DVOM set to DCV 20 range. All bulbs installed except left low beam. Ignition in RUN position, headlamps ON, low beam selected. In the left low beam socket, DVOM black probe to solid yellow wire terminal, red probe to yellow with black trace terminal. Careful you don't short the probe tips together, the fuse will pop. What is the voltage?

Leave the red probe where it is, (on the yellow/black trace) and move the black probe to battery negative. What is the voltage?

So get this, this morning I'm driving to work and the driver side low beam light (the problematic one) comes on and goes back off. During my lunch break I had one the fleet maintenance guys take a look at it.

The fuse for the driver side light was partially blown but had a good connection that not even the eye or prob was able to see if it was bad. The mechanic had to put a magnifier glass on it to show me how it was still able to make a connection.

He changed the fuse out and it's all good so far knock on wood. It amazes me how the fuse had blown but was still able to get a small enough current through it to make the eye think it was good. Thanks for your assistance, it's was really appreciated. :icon_bike:

I'm glad I found this place. Definitely sticking around.

That's pretty odd. Both left bulbs, (high and low) get voltage from the same fuse. Odd that only the low beam was affected. Oh well, like you said, knock on wood ;) Hang on to that DVOM ;)

HA, the next test, (post #45) would have found it.

Well he did also mention that I may want to keep an eye out on the passenger side low head beam connector. He had to play with it some. He did the same voltage test we went through last night. When he got to the next step (post #45) he got a 0 reading. When he checked the fuse it read fine but them pulled all the fuses out and put them under a magnifier and saw what the issue was.

But my question is can a fuse blow like that but still have enough connection that it can still make contact? he showed me the bad fuse but I threw it away. Normally a fuse will blow in the middle, but this blew under the colored part but had a little thin line still connected.

I've seen fuses come apart like that, (not actually blow) and it's rare, (defect when manufactured). When that happens, resistance goes up. When circuit resistance goes up, either positive or negative, bulb intensity goes down. If the resistance gets too high, it won't work at all.

The only explanation I can think of, is the high beam bulb draws more current than the low beam bulb. The higher current draw may have been enough to "weld" the fuse back together, but that doesn't explain why the low beam was dim, it should have worked too.

Interior lights you requested from me by email.

https://app.box.com/s/ayh60us55oqw3hpajopo