Under Hood Light not working

fiily · 04-29-2015, 06:33 PM

Can someone please tell me the correct # bulb I am supposed to be using for the under the hood light.

I bought the 1156LL bulb, but the light won't illuminate. I have cleaned the contacts, run a meter across the hood light switch and I am getting 9.75v with the dash light switch to parking lights and fully on.

I also took the new bulb and verified it working by placing it in the rear taillights and it worked flawlessly.

From what I have gathered, is this the correct bulb 1156LL or should I buy the 5008/r10W Bulb or am I off on some wild goose chase?

Bradical · 04-30-2015, 03:18 AM

9.75vdc across the switch is indicative of the switch being open. You have measured a 9.75vdc difference between input and output- that's your problem. Jump the switch out and your bulb will light up (if your lights are on)

fiily · 04-30-2015, 08:59 AM

Quote:

Originally Posted by Bradical

9.75vdc across the switch is indicative of the switch being open. You have measured a 9.75vdc difference between input and output- that's your problem. Jump the switch out and your bulb will light up (if your lights are on)

How does one jump this switch? Thanks Bradical.

Bradical · 04-30-2015, 10:40 AM

Simplest way would be to cut the wires going to the switch and wire-nut them together, otherwise you will have to trace out the wires and see if a jumper can be installed. Another idea is to remove the wire from the switch to the bulb and put a jumper between the bulb socket and +12vdc

fiily · 06:32 PM

Got it working, I disassembled the socket holder, used 80, then 1000 grit sandpaper to take the years of crud of the metal bracket front and back, along with the screw, the inner bulb holder, the mercury switch metal tips on either end, and the inner brass connection/brass hat that covers the mercury switch.

I used a 5008LL, but I believe the 1156LL works fine also if you cannot find the 5008LL bulb.

After sanding the brass "hat" and every metal piece I could find on the hood bulb unit, I used some electric parts cleaner that I bought from the auto parts store, sprayed the brass connections (hat and inner connection point in plastic holder, reattached everything, bolted it to the hood and voila!!

Don't use the electric cleaner on the mercury switch!!!

Light finally.

Created a YouTube video for future reference so people can watch and learn down the road if this happens to their 944.

Cheers

https://youtu.be/Eh8J6gsWbn4

Here is a picture of the complete light socket unit disassembled, you shouldn't have to cut the wire, just feed it through the metal holder to the point where you can get some sandpaper inside of the bulb holder and clean it up, then pull the wire from the backside and reassemble it.

If you look at the end of the cut wire, you'll see the brass end, that sits inside the black plastic holder and the wire that leads to it was cut for simplistic cleaning. The brass hat, the metal end of the wire, the nasty scaly bulb holder outside and inside were cleaned up with sandpaper. If you look at the mercury vial, clean those two metal tips ends too.

curtisr · curtisr's Garage

+1

Bradical · 05-01-2015, 10:24 AM

It's worth noting that you have a car with a mercury switch, which I believe is an early car thing iirc. My '87 just has a simple micro switch that is closed when the hood isn't pushing on it.

fiily · 05-01-2015, 10:38 AM

Quote:

Originally Posted by Bradical

It's worth noting that you have a car with a mercury switch, which I believe is an early car thing iirc. My '87 just has a simple micro switch that is closed when the hood isn't pushing on it.

I have an 88 944, your's sounds similar to an aftermarket hood switch wired to 12VDC, like a alarm system hood switch when opened it closes the loop when grounded and triggers the alarm, but in your case, it triggers your under hood light to go off.

Either way, it works and I can cross that off the little annoyances list I have had with the car for a couple of years now.

Volhv · Volhv's Garage

That picture looks mighty familiar.

That wire did not need to get cut.... oh well that's what solder and heat shrink are for.

Cool video, the underside of your hood is so clean!

fiily · 07:54 AM

Quote:

Originally Posted by Volhv

That picture looks mighty familiar.

That wire did not need to get cut.... oh well that's what solder and heat shrink are for.

Cool video, the underside of your hood is so clean!

I had a cold so I was very congested in the video.

Its your pic

Clean car, happy car!

black944 turbo · 05-04-2015, 05:26 AM

Thanks for doing this, mine just stopped working. Now I have a new project.

Gawernator · Gawernator's Garage

nice man

fiily · 05-04-2015, 03:02 PM

Glad to help. Sorry about the lighting, my garage isn't bright, but at least the video came out viewable.

black944 turbo · 05-04-2015, 04:33 PM

Just checked it and I have no voltage to the switch or at the connector on the bottom side of the hood. Any suggestions on were to test the wire inside or what fuse it is tied to?

fiily · 06:52 PM

Did you have your parking/headlights on? The under the hood bulb doesn't work without 1 of the 2 on. Also parking lights and up on your directional like taking a right works too.

You need to push the hat down a bit with your +probe so it makes the circuit complete, just imagine it like your lightbulb in there has to compress everything to complete the circuit.

If that doesn't work, the easiest would be check/clean your fuse for it, and verify that it's good, then disassemble the unit and scrub down the brass hat and the mercury switch end pins, 80/320/800/1000/2000 grit on the brass items if you have it. 800 and higher on the mercury switch end pins. (DONT DROP THE MERCURY SWITCH, WEAR GLOVES....CAREFULL THAT IS SOME NASTY STUFF!!!!)

That under hood light wire runs to a 4 or 5 pin connector hiding in a cubby in your hood. I pulled mine out somewhat in the video, you see where the wire is running inside the hood.

Check there 1st and see if you have voltage there, brown is ground, I forget which is 12+, just use your meter and remember, parking lights/headlight must be on to get current running to the hood light.

Post results, and we can go from there...hopefully not chasing wires everywhere, but if need be, those wires off the molex connector run by the driver's side, down the firewall, under the dash....a rat's nest.

black944 turbo · 05-05-2015, 02:50 AM

I checked all of that and unfortunately I have no power at the connector ( the one hidden in the hood). I am not sure we're to check from here.

fiily · 05:14 PM

Quote:

Originally Posted by black944 turbo

I checked all of that and unfortunately I have no power at the connector ( the one hidden in the hood). I am not sure we're to check from here.

The 1st picture is where your wire leads from your 5 pin molex connector from the hood light goes down into the rubber grommet by the fuse box, then underneath to the rat's nest which is picture # 2. I don't have a wiring diagram to reference, but hopefully some kind soul chimes in and leads you in the right direction. I'll keep looking to see what I have saved for wiring diagrams on my pc.