I recently got an underhood light for my '70 (originally equipped with one) but I have no idea where it should hook up. Also, even if I got it hooked , how does it turn on and off? I can't find a switch anywhere. Thanks a lot.

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1970 Chevy Custom El Camino aka Kaileigh
Green Mist & Silver w/Green Vinyl Top
350ci/300HP 4bbl & Factory Dual Exhaust
Non-SS with Factory Rallies!
TH-350 Automatic - 2.73 Posi Rear
My El Camino Home Page - www.dreamelectric.com (http://www.dreamelectric.com)

I'm am familiar with the 69 Chevelle and I'd guess that the 70 is probably the same. To be sure, get a 1970 Chevelle assembly manual and it will tell you where to hook it up. For the 69, if it is a big block it goes on the passenger side of the hood, on the underside support structure where the hood insulation is at its lowest point (hood open). There should be a couple of predrilled holes or dimples there. If it is a small block, just the opposite side. It basically goes on the side with the oil dipstick. Electrically, the one you bought will probably hook up at the horn relay. You'll have to route the wiring there.

The 69 hood light hooked up in two possible places, if on the driver's side it went to the horn relay, if on the passenger side, it spliced into a wire near the heater box.

The switch for the light is built into the light itself. It uses (I think) mercury that makes a contact when the hood is opened.
When you hook up the light, all you are doing is hooking up a hot lead to the light, the ground is to the body itself.

Good Luck.

It has a mercury switch similar to the trunk light, but I don't know where it should hook up. Although, on my Cutlass, it is tied into the headlight switch so that it only comes on (with the hood open only) when the lights are on. I would expect the Chevelle to be similar.

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Tom Parsons

On the Chevelles I had the hood and trunk lights only worked with the lights on. Wired this way there is no chance of the switch malfunctioning and running you battery down.

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Philip Valentine
Gold Member #42
"Perseverance is not a long race; it is many short races one after another."
philip@chevelles.com

Anyone know for sure where it connects? I got my underhood light of an '88 Cadillac in a salvage yard but I didn't see any mercury switch inside it (maybe i missed it). It sounds like hooking it up to the horn relay is right but which terminal? If it hooks up to the headlight wiring, what color wire? Thanks a lot.

Found it! Page 492 in the 1970 assembly manual OPTION U26


The light is attached to the hood via two screw. It mounts on the driver's side just below the right-most(driver's side) lower hood insulation pad. look for 2 pre-drilled dimples.

The wire follows wiring harness (taped and strapped) that goes over the driver's side wheel well. It finally connects to the horn relay--appears to be the outermost terminal.

I'm assuming it is mercury switch, because isn't the horn relay always hot with +12v?

Shawn, you won't be able to see the mercury, it's a potentially toxic substance and would be sealed inside the lamp base. Try hooking yours up to power and tilting it and see if it goes on and off, if not, back to the junk yard to get and earlier one.

Hope this helps.

Thanks a lot Coppertop. That helps a lot. I haven't seen my car for a while so I don't remember what the relay looks like off the top of my head. I know there's a terminal on it that has a label on it either BAT or +. Is that the one it should hook up to?

Shawn, that would make sense to me. If it is a mercury switch light or in other words, a light that doesn't need a separate switch, a BAT or + that is always live should work. That way the light would have power anytime you need it.

I'll see if I can scan that page for you, although the factory drawings aren't very specific.

I'd check the horn relay on my '70 for the connections (even though I don't have a light) but the car isn't here with me http://www.chevelles.com/forum/redface.gif