When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
is the mercury switch portion in the piece pictured above? there is a round black plastic inline connector piece further down the wire on the engine bonnet. is
that the mercury switch?
I took that switch apart. no mercury inside....just a straight metal set of prongs to where the bulb attaches. the issue is the connector that goes onto the switch pictured above. plastic pieces are
broken inside that keeps tension on the prongs when it is connected. when that plug is disconnected, the 2 metal flat blade connectors inside have 12V.
now, to find one of those connectors....I'll take a pic and post to see if anyone knows where I can get one.
I just tested the light with new bulb with 2 wires directly on the battery. the bulb lights up fine. so I'll need to get a new connector as shown below that goes into the above pictured light switch.
Last edited by mackendw; Aug 16, 2024 at 10:37 AM.
Reason: spelling
Rockauto has them (T5) for as little as $.23 each and if purchased at same time as larger order may not even increase the shipping expense of the larger order.
The electrical connector is probably a wrecking yard only acquisition
found the problem. took the mercury switch apart ....the 2 halves just press together. On one side is an L shaped wire lead that connects to the back side of the mercury filled
capsule. on the other wire side is a copper tang with a spring on the end leading out of the case. presumably when the hood is closed, the mercury is in a disconnected state.
then when you lift the hood up at a specific height the mercury falls to the bottom completing the circuit.
lof of rust on the spring and it was pretty seized. soaking in vinegar for 4-5 hrs...will see if that frees it up.
testing the mercury switch using continuity...when the wires coming out of it are point upwards, there *IS* continuity....ie: the circuit is completed. if you
simulate closing the hood at around 1/2 to 3/4 the way down, it loses continuity...so it would seem like it is working as it should.
now, the problem...there is a 2 prong connector for the wires coming ouf of the mercury switch to the wire harness. one of the wires going into this
plug from the truck going towards the firewall is live (12V). the other wire nada. when this connector is plugged in, it *SHOULD* be completing
the circuit as there is continuity being provided in the mercury switch when the hood is up (tested). but, when I plug the connector in, I lose
the 12V.
does this mean there is a short in the mercury switch?? even though the continuity test is good?
next test...loop the wires going to the mercury switch to see if bypassing it the light works...
[result]...fail. this is confusing. I can put 2 wires from the POS & NEG battery terminals to the light and it lights up no problem.
I have 12V on the green wire going to the light switch in its place and a ground black wire (screwed to the mounting plate for the
mercury switch) and the freaking light will not light.
resolved. broken wire from wire harness. looks like corrosion. soaked in vinegar for a while ...getting solid 12V now.
now to get the mercury switch mounted in the correct position so it shuts the light off when the hood closes.
the hood was replaced at some point before I bought the truck and they just installed the bracket for the hood light mercury
switch whereever without testing it.
resolved. broken wire from wire harness. looks like corrosion. soaked in vinegar for a while ...getting solid 12V now.
now to get the mercury switch mounted in the correct position so it shuts the light off when the hood closes.
the hood was replaced at some point before I bought the truck and they just installed the bracket for the hood light mercury
switch whereever without testing it.
I took my wiring and installed a cheep toggle switch in line with the ground. I work a bunch under the hood during the day. Now I don't have to worry so much about draining the battery. At night or broke down these under the hood lights are great, I now have the option. To shead light or not to shead light, that is the question.
I took my wiring and installed a cheep toggle switch in line with the ground. I work a bunch under the hood during the day. Now I don't have to worry so much about draining the battery. At night or broke down these under the hood lights are great, I now have the option. To shead light or not to shead light, that is the question.
yes, I considered going this route until I saw the price of what they want for them. either I'm too scottish or things are getting out of hand.
resolved. broken wire from wire harness. looks like corrosion. soaked in vinegar for a while ...getting solid 12V now.
My hood light worked before I disassembled the truck but not now. I haven’t tried to get mine working in a while so I’m not sure where I left off. I had power all the way to the part in your first post which is why I bought a new one. That didn’t work so I liberated the one from the Bronco with the same result. I didn’t check individual wires for a break. What area did you find the bad wire- on the hood or in the harness on the cowl?
I was not getting a clean 12V at the connector that went into the mercury switch...so I worked my way back on the power wire (green with white stripe)
that went down to a wire harness on the driver side firewall area. the wire connects to a rectangular plug just out of the wire harness. at that plug I was
getting a clean 12V... so my problem was corrosion more than breakage of that wire. I took my light off and put 12V from the battery + and the other pin
to negative to confirm the light worked first. hope that helps.
