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Underhood Light (+ LED Bulb upgrade) With Fiberglass Hood

This is a continued lighting upgrade project on the 1986 Buick Grand National we’ve been working on.

underhood light with LED

underhood light with LED

[so far: trunk light upgrade ; underdash light upgrade ]

Today’s new adventure:

Stock hood with underhood light?
No problem.

Simply replacing the factory GM bulb with an upgraded LED unit?
No problem.

However, once you upgrade to a lighter fiberglass Buick hood…
problem!

light fixture base hole contact

light fixture base hole contact point


You see, the only 1 wire that runs to the light, is a positive-only wire
(even though it’s black in color).

The light fixture is normally grounded through the hood.

Which now means the fiberglass isn’t going to work as a negative conductor any longer.

Solution?
Simply install a new ground wire attached to one of the bolts that secure it to the fiberglass hood.

new ground wire

new ground wire

And while you’re at it, install an LED bulb!

(they’re inexpensive & light up the engine compartment MUCH better!)

PARTS:

* underhood light fixture (this Buick GN was missing it. $20 on ebay).

* 2 bolts, 2 nuts & 4 lock washers to secure to hood (1/4″ x 3/4″ long stainless steel, home depot, about $1.50)

* LED bulb (varies depending on which version you get. $3-$10 on ebay).

fiberglass hood light fixture position

fiberglass hood light fixture position

* new ground wire (free, had stuff floating around garage; but you will need 2 ring connectors & a 36″ piece of wire {we used 14 gauge} ).

[note: 36″ may seem like its too long, but we ran it through existing/added wire loom & since the wire runs from the light then down, then left, then over to the mounting point, it’s just the right length.
You may need more/less depending on where you mount/ground it.]

TIME TO INSTALL:

* less than 1/2 hour.

attach ground wire

attach ground wire

HOW-TO:

[note: the fixture we bought had a slightly rusty base, so we sanded it down & painted it black.
On the drivers side hole we took a round file to it so as to have a good connection for the ground wire]

 
1. remove old bulb (if applicable) & insert new LED bulb.

2. figure out where you are going to mount the light fixture.

light attached to hood

light attached to hood


3. drill 2 5/16″ holes in hood

(aligned to the mount holes in the light fixture).

4. make the new ground wire.

 
5. place a washer on 1 bolt, attach ground wire, insert thru the drivers side hole of light fixture, stick bolt thru hood hole & secure with a washer & nut.

ground to intake bolt

ground to intake bolt

6. attach the other bolt.

 
7. take the end of the ground wire & mount it to a good ground.

(we used the coil bracket intake bolt on the drivers side).

 
8. plug in the hotwire to the original wire connector.

9. cover wires with engine loom.

 

attach to factory connector

attach to factory connector

10. TADA!

I have seen the light….

 

Fascinating upgrade, huh?

 
Perhaps not, but when your turbo buick doesn’t have an underhood light at all, this is a tremendous improvement!

(same goes for the difference of the stock light vs the LED bulb!)

cover with wire loom

cover with wire loom

finished underhood light with led bulb

finished underhood light with led bulb

.

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