No 12V power to underhood light in my 68 Cutlass. The light works as it should when connected directly to the battery and all the other stuff on that fuse works.So, is there a connector involved somewhere that I can check? Or is it a bad wire that disappears down somewhere into a huge harness?

 

I am not sure of the operation on a 68, but did you try with the parking lights turned on?

 

The under hood light is only powered if the headlight switch is on. This prevents running the battery down if you leave the hood up during a lengthy repair.

 

Good idea I will try the parking lights/headlights on. I couldn't figure it out from the wiring diagram.Thanks for the help. I'm still learning about this great car.

 

I thought the '68 underhood lamp was connected to a hot 12v wire (black) that passed through a grommet in the firewall (below and to the outside of the brake booster) and piggybacked into a hot connecter in the fuse panel such that the light comes on when the hood is raised without having to turn on the parking lamps. The '69 underhood lamp connects into a brown wire that passes through the firewall at the same location as the black wire for the '68, and then I believe connects into the fuse box where the parking lamps are connected in such that the underhood light will only operate if the parking lamps are on.

Randy C.
'68 4-4-2 convertible
'69 4-4-2 convertible

 

IIRC, I think you're correct. Wasn't/Isn't the underhood lamp a Mercury SW which activates when the hood is open?

 

Yes, mercury switch for both years. I believe the mercury switch underhood lights lasted several years.

Randy C.

 

Yes there is a mercury switch. My 70 and 71 have a mercury switch but both require the headlight switch to be on to power the circuit. Lift the hood and the light is not on until the headlight switch is pulled to position 2 or 3.
I guess 68 is similar but do not know for certain.

 

'68s are the same. Mercury switch turns off the light w/ the hood closed (no need to have this on going down the road at night), and the headlight switch interlock prevents battery drain during long hood-up intervals during the day when the light it not needed (or useful).

 

My experience is that the '68 model year is wired differently than the '69 model year. I've studied the wiring diagrams in the '68 and '69 chassis service manuals and there appears to be no connection between the underhood lamp and the parking lamps for the '68 year. It does appear that the underhood lamp for '68 is connected into the clock/lighter/courtesy lamp circuit which would keep it hot at all times. Conversely, there is a direct connection in the '69 wiring diagram between the underhood lamp and the parking lamps which would dictate that the parking lamps would have to be on before the underhood lamp would light up. Now, I'm not an expert at reading these diagrams and so I'm hoping someone else with better electrical expertise than me (mine is very basic!) can look at those diagrams and can either agree or disagree. My family has owned the '68 I have now since it was new and the wiring under the dash is still original. When I bought my '69, I thought the underhood lamp was burned out so I bought a new one and it didn't work, either. That's when I discovered that the parking lamps on the '69 had to be activated before the underhood lamp would work and I ended up with an extra bulb.

Randy C.

 

Thanks for the info guys. The system works as it should through the headlight switch. That would have been a good tidbit of information to put in the owner's manual. As it was when I opened the hood of my new car, the light was disconnected at the connector and the wire was dangling down. I assumed that the previous owner disconnected it to keep from depleting the battery when the hood was opened. After installing the battery. I plugged in the connector and, of course, got no light. I replaced the bulb, still no light. I removed the light and bench tested it....works great. Checked the voltage on the dangling wire....Zero!. Checked the fuse...It's good and all the other lights on that fuse work. Got out the wiring diagram and tried to trace the wire where it disappeared into a harness. Then I contact this forum and Voila!!...It'salive...It's alive!!!....What a great resource this forum is. Thank you all again