Wondering how the trunk lite on a 75 Olds Cutlass is activated? Mine appears to be wired in where the original one was and is but was changed to a LED style lite, but it's not working?
Got a pic maybe to assist? Thanks

 

Mine is hooked up but does not work. Bulb and fuse are both good. I have not crawled up in the trunk to trouble shoot it.

 

I don't know if the trunk lamp's mercury switch will work with an LED bulb or not. Try putting a regular 1003 bulb in and see if it works.

 

Seems that it would since the mercury switch just makes and breaks electrical contact, the same as any mechanical switch.
This is assuming just the bulb was changed from an incandescent to an LED, but re-reading the post it may be the entire socket (which incorporates the mercury switch) may have been changed. If that’s the case, no telling what is controlling power to the bulb.

 

Original fixture is not there. I can maybe try and find a replacement fixture. Also, I have not checked the wiring (voltage) to the LED fixture they installed. BUT, LED's may be dependent on polarity too! I'll do more checking. Got a pic of the fixture I should be looking for?
Bob

 

If the socket with the mercury switch was changed, you’d think a manual switch would be installed somewhere. Otherwise, what was the point?

 

exactly..... then I also read that the light switch would have to be pulled out to the parking light position then the trunk light would activate.
I'll have to try and find the style of light to install and go back to original. I see a couple after market lights but they don't seem to have the mercury switch.

 

I don’t think the trunk light would be connected to the headlight switch - it needs to come on when the trunk is opened no matter what’s happening with the headlights/parking lights. That’s the way the earlier lights are, with either a mercury switch or a mechanical switch with an arm activated by the deck lid hinge position.

Have you checked for voltage on that switch wire with a meter or test light?

 

You likely won’t find a new one as mercury has been deemed evil and must be removed from the world. I’ve seen switches in other applications using a steel ball instead of mercury as a workaround since mercury became evil.

 

Seemed odd to me too that this was the way the wiring was! Car is in the shop right now (new master cylinder being installed.). Good story, first 20 mile trip and had to be towed home! Anyway, going to check voltages etc when I get the car back.

 

Trunk lamp is wired into the DOME/CTSY circuit. It will be powered at all times.

Earlier cars wired the trunk, underhood and glovebox lamps thru the park/tail section of the main light switch.

Unless someone has an NOS or good tested used trunk light assembly IDK where you might find one. After 50 years I wouldn't trust a junkyard part, but all the 73-77 GM A-bodies used the same trunk light. I can't swear to it but the full-size cars probably did too.

What you're getting into is why I'm not a fan of putting LED lamps in an application that didn't come with them.

 

An LED would work fine as long as there is a switch to activate it when the trunk is open.

 

The ancients from ca.1500BCE found it quite useful. Course it did make hatters mad.

 

Yeah, but they sure made some nice head coverings.

 

So how/where is the switch to turn that trunk light on when the trunk is opened.? Is this that mercury switch someone mentioned?

 

Pretty simple demonstration and visual of how a mercury switch works.

 

This is a typical 1970s GM trunk lamp and bracket. Mercury pill switch is in the bulb holder.


If you look close you'll see someone has installed an incorrect dual-filament bulb 🙄 , hopefully just for illustration purposes. But it makes you wonder if some of these people can change a light bulb in their own home.

 

This is a kinda generic 1970s GM trunk lamp mounting diagram.

 

Perfect, thanks much, this helps.

 

I put led lamps in my trunk, works great. Best thing is when I'm at a show I don't have to diconnect my battery as the current draw is so low.

 

Thanks, good idea.