For my '71 cutlass convertible, I picked up the kit to replace the light under my hood (which has never worked). It states in the instructions that the factory hook up for this is to connect the wire to the horn relay and that the light will then operate off of a mercury switch. However, the light that is there now does not. Was it factory to connect this light to the horn relay?

Also, I was thinking of replacing the light in my trunk when I noticed that there is no light assembly in my trunk! Was there a trunk light in the '71 cutlass convertible, and if so, where was it located at so that I can install a new/replacement?

 

Check the CSM wiring diagram. Most of the underhood lights only work with parking lights on and are fed from light switch.

 

I don't know what "kit" or instructions you are referring to, but the factory under hood light connects to a specific pigtail feed that breaks out of the main harness under the brake booster. There will be a single Packard 56 connector body on a single wire that the underhood light plugs into. And be aware that while the light uses a mercury switch, it only gets power when the head or parking lights are on. This way, the light doesn't stay on while you have the hood open for repairs and run the battery down.

 

This may or may not be the case, depending on application and year. I have seen 72 GM vehicles with the convenience lighting package, hood and trunk lights that activate upon opening that lid, and they will run without parking lights. Pain in the butt to show at a car show, have to take the bulb out.

 

This thread will help ya...
https://classicoldsmobile.com/forums...unk-light.html

 

The OP has a 71 Cutlass. The underhood light works as I described it.

 

It's under hood lamp week @ CO!

 

Thanks for the info guys. As usual, it was spot on! By the way, here is the link for the kit that I was referring to.

http://www.opgi.com/cutlass/1971/ign...iring/LP26872/

Yes, I know how some people feel about OPGI. But they were the only place that I could find that had a part even remotely close to the one that I needed.

 

Didn't notice your advice was year specific. Wonder why it was different in 72? Probably a pain in the butt to use, turning on the parking lights to see in the trunk.

 

This is something I've always wondered about with the under hood light. I know that when my '68 4-4-2 was new (my dad bought it new) the under hood light worked when the hood was up, regardless of whether the parking lamps were on or not. When I finished the car's restoration in 2007, we had somehow hooked up the under hood light so that it only came on with the hood up AND the parking lamps on. I studied the way the harness was hooked up and discovered that I hadn't connected things quite right, according to what I saw in the electrical diagram. When I rearranged the connectors and the under hood light wire at the fuse box, and put things back together the way (I believe) the wiring diagram says to do it, my under hood lamp now operates like it did when the car was new. Is this something the assembly plant would have changed around over the years? Or am I reading the wiring diagram wrong? Just curious!

Randy C.

 

My response was to the OP's question. The underhood light is the only one that is wired to the headlight switch. The trunk light is powered all the time and only uses the mercury switch. Again, I assume the underhood light was wired that way to avoid running the battery down if you leave the hood open during a repair.

 

On my 1968, the trunk light is on when the trunk is open. There is no way to switch it off.

The under hood light is on when the ignition is on (or in accessory) and the hood is open. This works for me since my hood is open a lot.

 

It's not. The 72 under hood light, trunk light and interior convenience group works exactly like the 71.

 

Joe,
One small correction to your most recent post, the trunk light is not activated by a mercury switch, but by the little lever on the side that moves with the trunk hinge.

 

From at least 69 back the trunk lights were operated by a mercury switch as Joe said. sometime in the early 70's they changed to the lever type.

 

Sorry, you're right, I was thinking only of the '70-'72 cars.

 

Scott, you're comment is correct. The OP was asking about 71. FWIW, the vert uses a slightly different trunk light adapter than the fastback designs.

 

Interesting. Guess Chevrolet beat Olds in that one.

 

Which part did Chevy beat Olds on? The interior lights are triggered by door jamb switches (same as Chevy) and the trunk light is triggered by the deck lid arm movement (same as Chevy?). The trunk light (70-72) has a swing arm contact switch which I believe is the same as 70-72 Chevy?

The underhood light for Chevy I'm not that familiar with, but suspect it's very similar with a mercury contact and lights on required? I've never tried this, and I can't right now, but I wonder if turning the rheostat on the lights to full on will also turn on that underhood light when the hood is raised.

 

Neither hood nor trunk require parking lights on to work on a Chevrolet.

 

Ok, my 72 Cutlass doesn't require parking lights to trigger trunk light. So the hood light in the Chevrolet is triggered and powered by raising the hood? Is that even when you don't want it on?? Not sure I understand the logic of that. Must be a battery killer at car shows.

 

I checked my handy 72 Chevy CSM, per wiring diagram, it goes from the pos power distribution block, through a 4 amp inline fuse, to a mercury switched lamp, which is then grounded through the hood frame back to the negative. This jives with how mine works.

As for car shows, I don't normally show with the hood up; it's an original car in good shape, but I can't compete against full restos or egregious chromers. Also, with the Longest Hood That Chevy Ever Made, I worry about wind. I did raise the hood last week, and you either pull the bulb, or simply not open the hood 100% of the way (it comes on about 90% of the way up.)

Mea culpa on the earlier error on the assumption of 72 Olds's being that way. Silly me, expecting GM to be consistent.

 

Anybody have the bulb numbers for the under hood and trunk lights? For some reason I'm having a hard time finding them. EDIT: One source says they are both #89 bulbs, does that sound right?

Thanks,

jpm

 

Yes, that sounds right. Both bulbs are a single element with one terminal and equally spaced nubs on the base.

 

My trunk light was a 631. Could not find it - may be obsolete.

I put in a 1003, which is too long and sticks out past the light fixture.

 

The #1003 puts out 189 lumens vs. 75 lumens for the #89. Lots more light but it will get hotter, although that's probably not anything to worry about in this application.

 

My 72 Cutlass trunk & hood bulbs are #631

 

The #631 is very similar to the #89. Both put out 75 lumens / 6 candlepower.
The 89 draws .58 Amps and dissipates 7.5 Watts.
The 631 draws .63 Amps and dissipates 8.8 Watts.

 

If I recall correctly, at least for the 70 and 71/72 A-bodies - For 1970 the hood light worked whenever the hood was opened, whether or not if the parking lights were on. The 1971 and 1972 models required the parking lights to be on for the hood light to work.

I believe this is one of the idiosyncrasies found between the three model years.

 

Here is a recent discussion on how it operates:
https://classicoldsmobile.com/forums...esy-light.html