1991 F150. What activates the engine bay light? Just bought this truck. Supposed to light up when you open hood?
Light bulb in place but looks burned out. Tried another bulb but doesn't light.
Tried tester light but can't get a good test... but not sure if my tester is grounded properly.

UPDATE: got a good test with tester now.

 

Mine seems to have a mercury switch.

 

Thanks! Got it working intermittently after I removed the housing switch from the hood. It only works if the wire is hanging and the bulb is pointed straight down. I 'giggled' the wiring where it connects to the housing and that doesn't affect the light operation... only orienting it up or down will turn on/off the light. Seems the mercury switch is partially working.

When I attempt to clip the housing back in place, I can't get the light on with the hood in the up position.

I suspect my mercury switch needs replacing. Wow, $100 at LMC Truck.

 

You are lucky. New $40,000 - $100,000 trucks don`t even get a light under the hood. I know mine does not.

 

They're a LOT cheaper at your local JYs, and you can choose from almost any 12V light. You can even put in an LED strip. This is the ~'90~04 style that I think you have now:



This is the ~'83~86 style, also used in some later Jeeps:



The ~'87-89 style uses an external tilt switch:



But with something like these...
...you can turn virtually any weather-resistant 12V light into a hood light. I used something like this to plug in a cheap LED strip to the original holder (like yours) in my '97 F250.
New $40-100K trucks don't need nearly as much underhood maintenance as 80s-90s trucks.

 

What is "JYs" ?

 

Junk Yard