84 944 na headlight switch electrical fire

[knucklebuster]

Hi, i have had a 1984 NA 944 for two weeks now, and this morning my headlamps wouldn't come down, then they would not come up. Fifteen minutes later I had smoke coming out of the headlight switch. I will be replacing the harness and switch this afternoon but I have tried to get the car started and it turns over but will not start. Any input will be appreciated.

[Granite 944]

Oh boy! THE infamous "headlight" switch! You may very well have MANY electrical problems at this point. Stop! Don't drive it/run it, and start getting educated about what all this can do, and entails.

Make SURE.......NUMBER 1 item.........all fuses are of the correct rating, AND IN the correct locations of the fuse boxes. Then........go from there. Check my signature, "electrical project". Do a search here on this site/forum, and on Rennlist.com. Lots of info, and horror stories. Not to worry, you'll get thru it! Welcome!

[SoCal Driver]

Was this after you put the 200 watt headlamps in it?

[NKN84944]

My switch failed on my 84 a little over a month ago. I had the correct fuse and correct headlamps in my car. The fuse literally melted internally. Some made comments that I was probably doing something wrong (like putting in 90/100w bulbs), but it was just simply failure of the switch. I did replace the bulbs as a precation though. See the link below (BTW the reason my #3 fuse was blowing before was that the fan shroud was warped right under the thermofan switch where my radiator was leaking from shortly before I posted that thread and rubbing against the cooling fan blade which burnt out the motor ) Luckily mine did not get as severe as yours and start on fire, my headlights just stopped working so I took the switch apart and realized that it was shorting internally creating heat that melted the plastic housing. The car is over 20 years old, and stupid electrical problems are all two common. I seem to have them almost every month. Make sure that your problem was not just the switch though as others have said and rule out all other possibilities (I did and there doesn't seem to be any other explanation but failure of the switch). Good luck getting that taken care of. See the thread here

[IceShark]

As noted, just about everything in the Porsche wiring is poor to horrible. It is just under designed for the task at hand.

As to your headlight switch smoking, I've given up trying to talk people out of putting in 90/100 watt bulbs on the stock wiring. I just tell them something is going to fail eventually and I hope nothing else burns up. You can get by with 90 watt on dipped/low beam for awhile. But at some point, especially if you take a drive at night for a few hours, the switch is going to go out or the wiring aft of the headlight socket will melt. The wiring has a double threat. It is way undersized for a 90 watt draw so will heat up from electrical resistance. And the bulb legs are, of course, connected to the filament which is pretty damn hot. That heat back soaks down the wire. If you run like that for very long odds of having the insulation melt off get pretty good.

Besides all this risk business, the big deal is voltage drop. Halogen bulbs vary light output at the 3.4th power to voltage changes. Drop voltage 15% and you just lost 50% of your light output. The other way around is eliminate the 15% drop and you will increase light by 100%.

So, check what bulbs you have in the headlights and go shopping for a new switch.

[SoCal Driver]

The plastic headlight switch also provides an unfused circuit to the headlight motor. If the wires in the loom to the motor have chafed and shorted then these can melt the switch.

All of the headlight elements have seperate fuses. These could have been replaced with over rated fuses if higher wattage lamps were installed. The fog lamps have a seperate relay.

Early three bladed cooling fans have an open cage ball bearing right behind the blades. Water will eventually reach this and rust them. This causes the motor to seize and blow the fuse. The later six bladed fans have a sealed ball bearing. Last much longer.

The circuit that caused the headlight switch to fail has to be identified. Just replacing the underdash loom and the switch may not fix the problem if the headlight motor wiring at the front of the car is worn.

[bigyagi]

yes, amen to all the above. you will have some real fun, taking out the front wiring harness.
after owning several british cars, with their inherently bad , and undersized wires, coupled with lucas components{aka, lucas, prince of darkness}, i should be used to this crap by now !

[IceShark]

Originally posted by bigyagi
lucas components{aka, lucas, prince of darkness}, i should be used to this crap by now !

I owned an Austin and what a nightmare on Lucas components. I was in London at a party and got introduced to the Chairman of Lucas. I couldn't help myself and the first words out of my mouth were "Prince of Darkness". That didn't go over very well. I was around 30, 6 foot and 185lbs. In pretty good shape. I think he would have thrown a punch at me except he knew he get the crap kicked out of him. That was the end of my introduction to him.

[bryanthompson]

haha, that's awesome.

[Moneyguy1]

Not all the headlight problems are the result of over sized bulbs. I had a 924 (same switch) in which the paint on the hood was ruined just above the motor. The motor relay internally shorted out one night and self destructed the motor and relay. Car was unmolested electrically.

[Slam]

Yove got lots of company - I had the headlight-melt sandwich too. As a matter of interest, I disassemble every old 944 headlight switch I can get my hands on. They're almost all slightly melted/burned. My mistake was to manually raise the headlights and then remove the relay on the motor. Luckily, a friend saw the smoke and we were able to get to it in time.