Under Hood Reel Light

[Machspeed]

One of my projects today was to clean up the under hood light and replace the blown bulb with an LED bulb. Got it all cleaned up, new LED bulb installed, bolted back in and plugged in to find it does not work. I've got voltage going in but nothing coming out. If I'm not mistaken, the light comes on when the hood is raised. What is the mechanism inside that makes continuity with the hood raised? Frankly, I really wished there was an on/off switch, as I hated it being on when working on it for extended periods of time.

Anyone delve into one of these? I did a search here and find 145 pgs of stuff on "What LED Bulb" but nothing on taking it apart and fixing it.    

[Vic Roma]

An internal mercury switch controls the light. A few forum members solder the mercury switch and add a toggle switch, but this can lead to battery drain if you forget to turn it off. Drill the rivets, clean the internals, check the wiring, and spring.

I have not done this, yet, but I will soon as mine died too. The wiring is so brittle, and the light won’t retract. I hope I get it working again. It’s not the most suitable light for the task, but it sure is a cool feature.

[Gary Lewis]

Yes, there's a mercury switch.  But the switch sits in a pair of contacts sorta like an old European fuse and the contacts are prone to failure.

And when you take the unit apart be REALLY careful not to let the spring loose.  I don't think there's any putting that genie back in the bottle.  DAHIK.

But I like the switch idea.  Think I'll do that.  I'll add it so I can turn the thing off when I'm working on the truck in the shop.  Not to bypass the mercury switch.  

[Machspeed]

Vic Roma wrote

An internal mercury switch controls the light. A few forum members solder the mercury switch and add a toggle switch, but this can lead to battery drain if you forget to turn it off. Drill the rivets, clean the internals, check the wiring, and spring.

I have not done this, yet, but I will soon as mine died too. The wiring is so brittle, and the light won’t retract. I hope I get it working again. It’s not the most suitable light for the task, but it sure is a cool feature.

Yes Vic, there are far better lights but I like my OEM stuff and want it to work. I've done some more web surfing and have come up with little. A lot of stuff on this light was posted ten years ago and pictures and such are gone. We need a nice "How Too" on this little gem.

It makes sense that the mercury switch is no longer available, but I found something on a replacement mechanical switch (ball tilt switch), albeit not sure where to acquire it. See below link.

Where did you read about adding the toggle switch?  

https://www.supermotors.net/registry/media/71664

[Gary Lewis]

John - We need that how-to.  Please write it.

As for the switch, I've Googled and the ones I'm finding are very low current.  The highest I've seen is .3A, which would probably work but is marginal.

However, I think I have a mercury switch from the light I disassembled where the spring went EVERYWHERE.  You are welcome to it.  I'll look later today to ensure I actually have it.

[ArdWrknTrk]

The true Garagemahal spirit!

Gary, if John intends to use an LED, 1/3A may be fine.

As you said contacts get crusty.

Mercury switches don't go bad. (unless the bulb breaks)
I still find old Honeywell dial thermostats from the '50's in homes that must have opened and closed millions and millions of times.

I also have probably 30-40# of the stuff from dentists drain traps.
When they would just dump the amalgam 35 years ago.

[Gary Lewis]

Yes, 300ma might be enough.  And the https://www.amazon.com/Gikfun-Switch-Sensor-Arduino-EK1044/dp/B00R2MQD1Y gets you 10 of them for $5.98.  You could put two or more in parallel but they won't close at the same exact time so the one that closes first would get the initial current.

[Machspeed]

Gary, with your input, I'll do it. Sounds like Vic may be able to provide some good input too. I'll probably take mine apart today for an inspection. Mine may just need some cleaning as it may be all gummed up inside but I also have some copper showing in some of the joints of the wiring.

Regarding your warning on the reel, I'm taking notice as I know how that scenario can go. If you couldn't get it back together, I certainly know I will struggle. When I split the case, am I at immediate risk of the reel unwinding? Also, do you know if one can access all the wiring without pulling the reel apart? I ask because I may be wanting to change the wiring from the unit to the light. I'd like a more durable wire and I don't need 16' of it. I also need to work on some of the wire that powers and grounds my unit.

Would also be nice to know if that "ball tilt switch" is still available as a replacement for the mercury switch, as I posted in my link above.        
 
Here's the part number:  YW1Z-15702-BA 14 degree Mechanical Hood Lamp Switch

[Machspeed]

Good points, Jim! You don't miss much. I'm gonna start referring to you as our forum "MacGyver"....LOL! Seriously think you can ingeniously fix anything with the least abundance of materials.

[ArdWrknTrk]

Being autistic and growing up dirt poor ingrained a sort of farmers resourcefulness.
I see alternate uses in all sort of things.
"But if", "Why don't" and "if you only"  All. The. Time.

Or with Gary's fire extinguisher, thinking there's nothing innovative about that.
Something just like it has been around 50 years or more.

I make odd connections because of how my brain is wired.

[Gary Lewis]

I'm happy to help.

On the reel, you can pull one side off, the side w/o the mounts IIRC, w/o having the spring go everywhere.  The reel stays on there fine if you are careful.

And I think you could drill the rivets but leave the unit assembled, pull the wire all the way out to the last notch, and then pull the cover.  That should let you replace the wire, although I've not done that.

But the spring will be wound tight at that point and you will need to be even more careful.  Maybe a clamp or a weight to hold the reel in place.

As for that switch, Lakeland Ford has one for $70.60.  How many do you want?  

[ArdWrknTrk]

Eeesh!

I bet they're under a buck from Digikey, Newark or Mouser.

[Gary Lewis]

Yes, if we can get the right part we can make it part of the how-to.  But I don't think it is going to be the one Ford spec'd.  

[ArdWrknTrk]

Could be a simple accelerometer switched relay.
That would duplicate a mercury switch in function.

[reamer]

LED lights are "one way" flip the LED's Plug around...

[kramttocs]

Gary's right about the spring. When I refurbished mine it uncoiled but wasn't bad putting it back together. Once you take a look at the innards, there's not much to the whole assembly and in addition to cleaning it also gives you the opportunity to wind it a little tighter if you want.

[Machspeed]

Thanks Scott, but I think I'll leave that spring be....LOL! When I got it apart last night I quickly realized why it wasn't working. The contact that touches the little mercury switch was not making contact. I attempted to move it and eventually broke it. The wire that was attached to the contact was also quiet corroded and it broke off trying to clean it. I made a copper contact using some copper tubing I had but I'm wondering if I should look into something like spring steel. Suggestions? Also, cleaned up all the contacts including the those on the reel. Suggestions on lubing those points? If so, with what?  

[kramttocs]

The spring steel question I'll leave to MacGyver
For the contacts, I smeared some dielectric grease on them. White lithium on the other non-electric moving parts.

[Machspeed]

That's funny, Scott! I'm actually looking forward to his response....where you at, Jim???

[ArdWrknTrk]

Me?

I think brass is fine as a contact.
There is spring brass, but that is kinda specialist and you'd likely find it from a clockmaker.

I've torn open a regular wall receptacle to hack a wiper contact before.

I'm not big on oils or grease in a dusty environment.
I would probably try powdered graphite since it's slippery and conductive.
It won't attract and stick to grit and dust.