Under Hood Light, Convenience Group

[andy72]

Time to clean up under the hood. 

The Mach I bought has the convenience group.  This is my under hood light.

The schematic I have says the under hood light it is a mercury switch light.  This sure doesn't look like one.

Is this the correct fixture/bulb socket?  It's certainly original.

The wire on mine is just dangling.  The schematic shows a 7.5 amp fuse, then connection to the plus side of the solenoid where all the hots are.

It must be an inline fuse holder?

Can someone detail how this light and connection is supposed to be?

Thanks

 

[red351]

It should be a breaker, not a fuse. The switch built in the socket. What you show is the same as mine

 

[Bill73Ragtop]

Here's a pic of what mine looked like

 

[SteveO_71]

The routing looks somewhat correct. If you want it to look more like Bill's 73 then the wire should be fastened to the hood by these:

https://www.macsautoparts.com/store/tail-light-wire-retainer-clip-white-plastic-before-4-15-70.html

If you want to replace/clean up the wire loom, you can use these parts from NPD:

https://www.npdlink.com/store/?p=catalog&mode=newsearch&search_str=15702-2a&parent=1&year=0

https://www.npdlink.com/store/?p=catalog&mode=newsearch&search_str=c-8965l-2&parent=1&year=0

 

[andy72]

Thanks, that's a big help so far.

I can't believe that little fixture is the mercury switch unit.  OK

I'll have to test mine.

Where does it plug in?  I lose the vision of the wiring in the picture when it drops down behind the air cleaner.

My wiring harness under the hood so far appears unmolested.

This assembly has an inline male plug on its end.

There should be a female plug in that region for it to plug into right?

Where is the "circuit breaker" located?

My 1972 schematic clearly shoes a 7.5 amp fuse between this light and 12V.

 

[SteveO_71]

There should be an inline fuse towards the end of the wiring. Then, on mine, there was an eye connector that connected to the 12v, probably at the starter solenoid.

On the original light, they used a mercury switch but on the repro ones, it sounds like a more mechanical thing since you can hear it moving back and forth as you tip the bulb part.

 

[andy72]

The routing looks somewhat correct. If you want it to look more like Bill's 73 then the wire should be fastened to the hood by these:

https://www.macsautoparts.com/store/tail-light-wire-retainer-clip-white-plastic-before-4-15-70.html

If you want to replace/clean up the wire loom, you can use these parts from NPD:

https://www.npdlink.com/store/?p=catalog&mode=newsearch&search_str=15702-2a&parent=1&year=0

https://www.npdlink.com/store/?p=catalog&mode=newsearch&search_str=c-8965l-2&parent=1&year=0

Thanks for the links.

The one from NPD says its "exact" but it's for a 69-70.

I guess the aftermarket doesn't have an original style for 1972.

I still can't believe there's a mercury switch inside the little square original one...

I get no continuity thru mine no matter what angle I have it at.

I'll soak it overnight in evaporust and hope to get lucky

 

[rackerm]

Thanks, that's a big help so far.

I can't believe that little fixture is the mercury switch unit.  OK

I'll have to test mine.

Where does it plug in?  I lose the vision of the wiring in the picture when it drops down behind the air cleaner.

My wiring harness under the hood so far appears unmolested.

This assembly has an inline male plug on its end.

There should be a female plug in that region for it to plug into right?

Where is the "circuit breaker" located?

My 1972 schematic clearly shoes a 7.5 amp fuse between this light and 12V.

The convenience package option, if I recall correctly, included the hood and trunk light, glove box lock and light, automatic seat back release actuators, etc.

Where does it plug in?  You should have an accessory wire that runs over the passenger side shock tower to cowl brace. On that wire is a single female plug. This accessory wire is connected to the solenoid or terminal block on the battery side. It feeds other non-switched features such as convertible roof motor, automatic seat back release actuators, etc. and is fused.

The light socket is grounded thru the mounting bracket and has the typical spring loaded (positive) contact in the middle of the socket base. When you press the bulb in it depresses the contact completing the circuit. When you tilt the bulb up the light will be off and when titled down it will turn on. Just as it would when opening and closing the hood. I have ahd a few where the positive contact is corroded/rusted or the mercury has managed to escape at some point. Clean up the contacts as much as possible, insert a working bulb, and ground it and give it 12 volts and just start tilting it.

 

[Bill73Ragtop]

I never put a lamp into the socket since it would stay lit all the time at an all day car show. Same with the trunk light (which is the same style light).

 

[rackerm]

Here is the trunk light mercury switch version. It has a different mounting bracket and wire.

 

[andy72]

Thanks, that's a big help so far.

I can't believe that little fixture is the mercury switch unit.  OK

I'll have to test mine.

Where does it plug in?  I lose the vision of the wiring in the picture when it drops down behind the air cleaner.

My wiring harness under the hood so far appears unmolested.

This assembly has an inline male plug on its end.

There should be a female plug in that region for it to plug into right?

Where is the "circuit breaker" located?

My 1972 schematic clearly shoes a 7.5 amp fuse between this light and 12V.

The convenience package option, if I recall correctly, included the hood and trunk light, glove box lock and light, automatic seat back release actuators, etc.

Where does it plug in?  You should have an accessory wire that runs over the passenger side shock tower to cowl brace. On that wire is a single female plug. This accessory wire is connected to the solenoid or terminal block on the battery side. It feeds other non-switched features such as convertible roof motor, automatic seat back release actuators, etc. and is fused.

The light socket is grounded thru the mounting bracket and has the typical spring loaded (positive) contact in the middle of the socket base. When you press the bulb in it depresses the contact completing the circuit. When you tilt the bulb up the light will be off and when titled down it will turn on. Just as it would when opening and closing the hood. I have ahd a few where the positive contact is corroded/rusted or the mercury has managed to escape at some point. Clean up the contacts as much as possible, insert a working bulb, and ground it and give it 12 volts and just start tilting it.

Thank you for the picture!  It's just what I was looking for.  The 12V comes from a second wire out of one of the moulded points.

Mine is broken off flush, right at the moulded rubber.  I hadn't even noticed it.  Explains why I didn't see an additional lug on the solenoid, or a female plug waiting for me on top of the shock tower brace. . 

I knew my car was very original but couldn't find the connector.

By the way, soaked my light in Evoporust overnight, it worked the next day.

Thanks again

 

[Carolina_Mountain_Mustangs]

I saw the comment about leaving the bulb out at shows to save the battery. You should put a quick disconnect on your battery so you can pull the knob off put in your pocket and just adds a little extra protection about someone stealing it also. They make them that are a blade lever but it stays with the car so anyone can close it and start the car in seconds. With the type with a knob you have in your pocket.

I always take it loose when I bring the car in also so there is no juice to anything while parked in garage.

Don't have a picture but they are pretty common in parts stores and ebay. Most MCA judges do not mark you down for them either.

David

 

[Raven]

Thanks, that's a big help so far.

I can't believe that little fixture is the mercury switch unit.  OK

I'll have to test mine.

Where does it plug in?  I lose the vision of the wiring in the picture when it drops down behind the air cleaner.

My wiring harness under the hood so far appears unmolested.

This assembly has an inline male plug on its end.

There should be a female plug in that region for it to plug into right?

Where is the "circuit breaker" located?

My 1972 schematic clearly shoes a 7.5 amp fuse between this light and 12V.

The convenience package option, if I recall correctly, included the hood and trunk light, glove box lock and light, automatic seat back release actuators, etc.

Where does it plug in?  You should have an accessory wire that runs over the passenger side shock tower to cowl brace. On that wire is a single female plug. This accessory wire is connected to the solenoid or terminal block on the battery side. It feeds other non-switched features such as convertible roof motor, automatic seat back release actuators, etc. and is fused.

The light socket is grounded thru the mounting bracket and has the typical spring loaded (positive) contact in the middle of the socket base. When you press the bulb in it depresses the contact completing the circuit. When you tilt the bulb up the light will be off and when titled down it will turn on. Just as it would when opening and closing the hood. I have ahd a few where the positive contact is corroded/rusted or the mercury has managed to escape at some point. Clean up the contacts as much as possible, insert a working bulb, and ground it and give it 12 volts and just start tilting it.

Thank you for the picture!  It's just what I was looking for.  The 12V comes from a second wire out of one of the moulded points.

Mine is broken off flush, right at the moulded rubber.  I hadn't even noticed it.  Explains why I didn't see an additional lug on the solenoid, or a female plug waiting for me on top of the shock tower brace. . 

I knew my car was very original but couldn't find the connector.

By the way, soaked my light in Evoporust overnight, it worked the next day.

Thanks again

Don't forget the ground! https://secure.cougarpartscatalog.com/71grndstrap.html?attribs=82

 

[70cobrascj]

Thank you for the picture! It's just what I was looking for. The 12V comes from a second wire out of one of the moulded points.

Mine is broken off flush, right at the moulded rubber. I hadn't even noticed it. Explains why I didn't see an additional lug on the solenoid, or a female plug waiting for me on top of the shock tower brace. .

I knew my car was very original but couldn't find the connector.

By the way, soaked my light in Evoporust overnight, it worked the next day.

Thanks again

Get a connector from a 70-71 Torino it has an in line fuse and the correct connector at the end. Mine is broke off also and I wondered what it hooks up too.
I’m going to mount a Torino one in mine.
It seems hard to find a correct 71-73 Mustang one.

 

[bkdunha]

Looks like everyone has contributed to getting you further down the path. That is the great thing about this community really helpful and respectable feedback. Just to add a comment on the light. My car has one and at shows the hood is always open. I just took a bulb and burnt it out with running a little more juice through it. That way at shows it is not drawing any power, but is still present in the socket.