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2002 chevy trailblazer_lt
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The under hood light found on the '02 uses a mechanical rolling switch. Over time, the electrical contacts inside build up resistance due to a number of factors (corrosion, grime, etc).

If you have one and it doesn't work, here are a few things to check (in order with the easiest first) . . .
- Pop the lens cover off and check the bulb to see if it's burnt out. If burnt out, replace it.
- Remove the electrical connection. With a simple automotive 12V testing probe, check to see if there's power in one of the two wires. The other one returns to ground. If the tester's bulb doesn't light (or whatever means your using to check for current show's it's dead), check the circuits fuse and/or wiring.
- If both of the above tests pass, then you've determined that the under hood light unit itself is faulty. This is usually due to the conditions I mentioned at the top. You could order a new one from your GM dealer for ~$30.00cdn (<---- note to those who don't have one and want to add it), or you could attempt to repair it yourself.

Instructions for repairing your under hood light
1 Disconnect the wiring from the unit and remove it from the hood. It simple pops off. It's not screwed on but clipped into two holes under the hood. Here is what it looks like upside down on a table.


2 Using a small slotted screwdriver, release the unit's housing clips and pop the cover off. (It's not screwed together).




3 Notice that the mechanical switch is simply a rolling weight that slides the contacts either on or off depending on the unit's orientation.



4/B] It's all these metal contacts the need their surfaces cleaned.


5/B] Lastly, when everything looks ready to go, simply put the rolling weight and sliding contacts back in the case and snap the cover back on. Reinstall the unit under the hood and reconnect the wiring. With a few grains of salt over your shoulder for good luck, you should have a working light again. :)
 

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2002 gmc envoy_slt
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110 Posts
Discussion Starter · #23 ·
Absolutly, at least the 02's have one! Haha
:thx While I'd gladly trade my underhood light for the ability to run an aux input to my hu like you 03 & ups can, I appreciate all the help! I'm off to clean my contacs, then clean my contacts! HA! :dielaugh:

I'll post on how it goes!
 

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2002 gmc envoy_slt
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110 Posts
Discussion Starter · #24 ·
It worked!

:hail::thx:hail: Thanks Blazin Bob for the explicit instructions & explanation. I took out the light, popped it open, sure enough, there was a little rust/corrosion on the contacts. took a little sandpaper to them, plugged it back in, and THERE WAS LIGHT! :woohoo: Took me exactly 4 minutes! TRAILVOY RULES!
 

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2002 chevy trailblazer_ls
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47 Posts
The fuse is #31, TBC4

I got mine to work, by checking all the fuses. I also cleaned the contacts in the light, but probably didn't have to.

If anyone didn't know off-hand, #31 fuse in the front engine fuse box, was the one that got me working. It's labelled TBC4 in the manual.
 

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2007 gmc envoy_sle
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47 Posts
I have fitted an underhood lamp and glovebox lamp (never fitted by GM on my 2007) but I need to wire them.
The Haynes manual wiring diagram indicates both lamps are fed by the same orange wire from the rear fusebox.
Is your underhood lamp fed from the front fusebox then?
It's a bit confusing. I don't know whether to run a wire all the way from the rear fusebox and through the firewall plus across to the glovebox, or if the underhood lamp was designed to be fed from the front fusebox while the glovebox lamp was designed to be fed from the rear fusebox.

Or was the orange wire run over the headliner?
Doesn't SOMEBODY have photos of where the original orange wiring was run for both these lamps???:confused:
 
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