Headlight switch question

[MidnightBlue83]

I was trying to change the headlight switch knob in my 83 6cyl Mustang and noticed that the switch was getting pretty warm. I pulled it and found that it was a cheap repro. I ordered a Motorcraft (with what it says for the Light Group option) but noticed it's a 9 terminal whereas the repro that was in the car is only a 7 terminal. Why is that? Is that the reason it was getting so hot? Will this Motorcraft work? Confused.

[kpippin1986]

I honestly have no idea if this could be it or not, but the 9 terminal might be for the cars with fog lights whereas the 7 terminal for the cars without foglights? A shot in the dark, I'm sure someone else with more knowledge will post something more informative than this lol.

[Quicksilver]

I can only add that my original headlight switch (and I have fog lights) started to smoke when I put my car back together.

I ordered a new one (not Motorcraft) and was asked if the car had foglights or not as there are two different switches.

New switch installed, all is well.

[KevinK]

The light group term is misleading. At the moment, I don't recall if it's interior lights or something else like fog lights. I know the light group switch is used on the SVO and my 85 McLaren Capri. The SVO has fiog lights and the Capri doesn't . The extra 2 pins is a seperate connector from the regular headlight plug. I'm leaning more towards the interior convience lights.

[9D83]

It's interior lights. Map lights, glove box, hatch light, etc. They are all switched. I think the extra pins are for the headlight buzzer. OP do you have map lights?Do you get a buzzer when you turn the key off and leave the lights on?

[SECESH]

Abnormal heating in an electrical device usually results from an excess of resistance. The switch contacts could be corroded for example, or a connector not making solid contact. Could be a partly broken wire.

[86GTdriver]

Abnormal heating in an electrical device usually results from an excess of resistance. The switch contacts could be corroded for example, or a connector not making solid contact. Could be a partly broken wire.

There's also the possibility of thermal runaway or excessive load, not from the switch, but from whatever the pins on the switch connects to. These early cars are loaded with insufficient AWG sized wire from the factory, then you throw 30yrs, corrosion factors and normal wear/tear and things like this occur.

If replacing the switch with a Motorcraft unit doesn't help, it's time to start troubleshooting. The smoking could be due to excessive load on the wiring from someplace if it makes multiple switches hot/burn. It's one of the main reason's people place relays on the head/fog lights. Ford could have done it back then to minimize the load the switches have/had to endure constantly and avoid things like this altogether but didn't. We're all familiar with the 87+ GTs having a similar issue with their fog light switches and starting fires for the very same reason; excessive loads and insufficient gauge wiring, which is why my only concern here would be if you were to replace it with an OEM part, it still may not fix the problem.

[MidnightBlue83]

Thanks for the responses. I did order a Motorcraft w/ Light Group because mine does have that option, but I don't have fog lights. I don't hear a buzzer when the lights are left on AND the seatbelt warning light (and buzzer too?) is not working. I wonder if this new switch will activate that? Also, it wasn't smoking, just felt the switch was pretty warm, approaching hot, and I don't remember that every being 'normal' on the other 67-73 Mustangs I have had.

[mb757]

Thanks for the responses. I did order a Motorcraft w/ Light Group because mine does have that option, but I don't have fog lights. I don't hear a buzzer when the lights are left on AND the seatbelt warning light (and buzzer too?) is not working. I wonder if this new switch will activate that? Also, it wasn't smoking, just felt the switch was pretty warm, approaching hot, and I don't remember that every being 'normal' on the other 67-73 Mustangs I have had.

The light group option, if my memory serves me correctly did have the two extra pins for to activate the buzzer. If you buzzer isn't working though, it may have been removed to prevent the buzzing. We used to take a lot of them out over the years as the customers requested that it be removed. If it doesn't buzz when you're done it may have been removed.

As for the over heating, we used to have a few that were overloaded with accessories hooked into the circuit that didn't belong. If there isn't any thing added to the circuit I would look at the plug in or connector that plugs into the switch. The connectors would corrode or open up causing a loose connection, creating heat and melting the plug in. If you need a plug in here's a chart from Ford with part numbers and illustrations http://www.fordparts.com/fileuploads...icationkit.pdf .

[grabbergreen84]

Look at your light switch connector, and see if it affords clearance for the two extra terminals on the new switch. I suspect that it might.

[MidnightBlue83]

So I got the new headlight switch. It actually has 2 more terminals in a separate little area behind the 7 terminals--for a separate thin rectangular black plug up in the dash right next to the actual headlight plug. So I plugged it into the switch but I don't really know what it's for and I don't hear or see anything different. I know my seatbelt light on the left little dash window doesn't glow if the seatbelts aren't buckled nor does a buzzer ring when my headlights are left on. Anyone know exactly what this 2 terminal plug is for that goes into that extra section of the headlight switch??