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Opinion on Electrical Issue

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Okay, so I'm looking for some opinions on a (another) problem I'm having.

When I pull my headlight switch, the headlights would come on but I had to wiggle it to get the dash lights on. This got worse and worse until the dashlights no longer came on with the headlights. Much to my chagrin, I also found out that, when the dash lights were not lighting up, neither were any exterior lamps except the headlamps (no tail lamps but the brakes still worked). If I pulled the headlight switch part way out, I could get the dash lights and exterior lights to come on without the headlights. My first guess is I have a bad switch and I've already ordered a replacement from the dealership. The thing is, however, is that when I pulled the old switch off, I noticed the harness was partially melted. Now I'll be honest, I do not want to splice in a new harness if I can avoid it but I want opinions on whether you concur its a bad switch causing the problems, to include the partially melted harness, or some other bigger electrical issue with the switch and harness being secondary effects.

Picture is below.


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<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vicsik1969</div><div class="ubbcode-body">I do not want to splice in a new harness if I can avoid it...</div></div> Darrin, you don't have much choice. Either buy the entire harness, or splice a connector to a NEW headlight switch. That one's trashed.

Cause of failure? Could be a few things. One fact is for sure, too much current caused this, aggrivated by loose connections. Resistance set-up, then arcing created heat which made the connections even looser, and it melted the plug.

Are there extra lights on these circuits? Are you powering a trailer? If so, run a pair of #10AWG's from your battery to your trunk, and use relays. OEM's don't allow for much more capacity than the car already demands. I'm surprised none of the wires are fried. The melted plastic must have smelled bad.

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Just to throw my 2 cents in here (I do know a little bit about this as an electrical engineer...)

Looking at the picture, I don't see any discoloration on the male tabs on the switch itself. The connector obviously overheated, melting the plastic shell. But again what you can see of the female connectors inside the shell look bright and shiny.

Usually, when you have a bad connection which causes increased resistance, therefore heat, therefore a worse connection, etc. eventually the metal connectors themselvs get so hot they either arc and melt (not as typical at 12V) or at least start to discolor through oxidation. Since the connectors look shiny, my bet would be on the crimp where the wire connects to the female side in the plug.

Usually these are made to crimp in two places; one crimp around the wire (to make the electrical connection) and one around the plastic insulation( to make a mechanical connection). Auto makers use crimps rather than soldering to do the job faster and cheaper, and to prevent cracking of the solder joint from vibration ( just ask any 80s Mercedes owner about bad solder joints in the AC control unit). I'd bet that either the wire crimps weren't quite tight enough, or the insulation wasn't stripped quite right originally and the connection got worse over time.

The bottom line is you've got to put a new connector on those wires one way or the other...

Has anyone else seen this exact kind of thing ( shiny connectors with melted wires or plastic) in other areas of the TC wiring? Would be good to know if there are particular trouble spots to inspect before everything melts.

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Jim, you just got me to look at the pics again. Aluminum and copper don't mix well. The TC 3rd brake light has a problem with aluminum contacts also.

I could have used your expertise 20 years ago when the main breaker on my house kept tripping after a new meter was installed. I had to pay the electric company to come out and clean the meter contacts. Never had a problem after that.

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its posible the plug in [female ] was not pluged in solidly and or the wire plugs in the connector were not pushed in to the fixture all the way ,not necessarly an arcing conditio but a poor or weak connection causing heated conectors ,they appear to be aluminium and they may not show heat like brass connectors . the female plug is a common conecter for chrysler and should be available ,the wires just plug into the plasic housing , this from an old man who spent several days hooking up headlites , fog lites ,park lites etc on a kit car and i cant even drive at night with these week eyes .there are several headlite switches like this on mopars ,mostly high end cars . the pull knob will vary .

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Bill, another thing - if they are Aluminum, that's another whole problem - We don't use Al wiring much in the US since the 80s because the expansion of the Al itself under load (just in normal operation) tends to loosen the connections. Commercial buildings using Al wire have to shut down every 3 years to check and tighten all the connections in all the panels in the building to prevent fires.

Al was cheaper, but a bad choice for high amperage connections (like lights...)

And Redman, you're right, Al doesn't show the heat like Brass or Nickle, at least until the Aluminum itself melts... and if the female connectors are Al and are crimped onto copper wire, that's a major problem right there. The Cu-Al joint could corrode and cause the bad joint in the first place.

It's strange where companies cut corners - look at the sophistication of the Oxygen sensor connector in our TCs sometime - there are o-rings built inside it to prevent water seepage. Guess they weren't so worried about the light circuits. Or overly worried about the EPA and the Clean Air Act.

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by the way dont forget to remove your rings and watches when reaching under your dash or any where there are elect connectors ,trust me you cant get them off quick enough if they make a contact ,play it safe .the old voice of experiance

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Are we looking at the same picture? By the way Darrin, you took a GREAT picture; in focus with good contrast.

I'm looking at STEEL terminals that are CRIMPED at each end, either by eyelets to metal plates, or around copper wires.

Every electrical engineer knows this is the automotive standard. (Get your magnet out and check it.)

Electrical Engineers also know that lead has > TWICE the resistance of iron.

Bill Reichert learned all about resistance and what it can do:<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Reichert</div><div class="ubbcode-body">...I had to pay the electric company to come out and clean the meter contacts. Never had a problem after that.</div></div>

None of our connections are ever soldered. Crimped terminal ends are far superior to solder connections because; wire to terminal resistance is nearly zero Ω, good vibration properties, wire flexibility is good, and the connection can withstand high temperatures. Lead/tin solder has high Ω-resistance and a low melting point, by comparison. Aluminum is too soft for these sizes, and has inherent problems. Copper can be, but is rarely used because it doesn't have 'spring memory' like steel does (for the female connector). It is common to find plated steel lugs that may look like copper or brass in blade-type connectors.

At 400ºF, steel turns ‘straw’ colored. (At 600º it turns blue-ish.) What solder connection can take 370º before falling apart?

Plastic melts miserably, and brass & copper turn black way before steel turns color.

Do you guys see the discoloration in the eyelets? Those are the ‘weakest’ connection points.

With excessive heat, brass discolors, anneals, and relaxes the connection forever (causing more resistance).

Look at the eyelet on ‘H’ connector. Clearly it is discolored from heat. I see a few more.

The mating plastic plug housing bears witness to the heat. Where did the heat come from?

That plastic socket has positive clasps that 'hook' into the headlight switch, so that can't be loose (or the cause).

Looking at the 'witness' scrape marks on the headlight switch lugs (Eg:B1), the mating female connector went all the way down...<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: simplyconnected</div><div class="ubbcode-body">One fact is for sure, too much current caused this, aggrivated by loose connections.</div></div> Lighten the current load on your switch. Today, we use relays for our headlight circuit.

Relays, mounted in the front of your car, keep wire lengths short and stop high current from going through your headlight switch.

Running six or twelve volts has NO bearing. Current demand (amps), determines wire, fuse, and switch sizes. - Dave Dare

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Dave, good point.

OK, let's look a little closer at this -

By the way I agree that the picture is great...)

The most melting is on the three center terminals, B2 (upper center in the photo), H (Left center) and R (bottom center). B2 is where the main power comes in to the switch for the dash rheostat and the parking lights front and rear. H is the output for the high/lo beam headlights, and R is the output to the parking lights. Makes sense, those are the circuits that draw the most power.

And you're right, in the picture those three terminals on the switch do look like their rivets are discolored (assuming they are all made of Zinc or Tin, solid or plated on steel) and not copper for just those three for the high current draw. I'm not sure, I've never had one of these switches out.

BTW, you're right that steel (iron) is half the resistance of lead, but Tin is a little less than steel, and Zinc is half that. Most rivets I've seen used in an assembly like this are either Zinc or Tin plated, and then a lot of the current flows through the plating. But even at these current draws (20A fuse for the whole parking light circuit) the resistance is so low that it's doubtful much heat would be generated in the metal. Biggest problem with solder in a car is manyfacturing cost and cracking due to vibration.

What would copncern me is why it is getting hot enough to melt the connector shell. Switches are pretty well understood technology; car companies have been doing this for a long time. After another look at the picture, notice the discoloration on the wiper arm for the dimmer control(just to the right of the round white ceramic part of the switch) where it touches the NiCr wire coil - it's either burned black/silver or it has a plated contact area there. If the switch wiper arms (which are hidden on the other side of what you can see in the picture) are designed the same, I'd guess that they started to burn as well and heated everything up, causing the melt. Could be caused by dirt getting in there, or condensation on the switch contacts. Could even be that the switch wiper arms had silver plating at the contact area which just wore off with age and use. Plating wears off, resistance goes up, and it gets hot.

Darrin, this makes sense for your symptoms too - if the switch resistance was getting worse over time, making the lights dimmer and dimmer, that is what you would expect.

Is there any visible damage to the plastic of the switch itself near those center terminals? If so, then it certainly was the switch itself that caused this. If not, then I'd still take a close look at the connectors in the plug. Do any of the central wires look melted where the wires come out of the plug? If not, then it was probably in the switch. If you can pick any melted plastic out of those center connectors and feel comfortable that they will make good contact with the new switch terminals (and don't mind the custom melted plastic look of the connector) you're probably safe to plug it back into the new switch and can do without splicing the harness, etc. I'd probably try that, and just pay close attention to any future symptoms in the light system which might indicate the connection getting bad again.

You could also try plugging in the new switch to the old harness/connector, starting up the car (so you get full voltage), turning on all the lights (with the switch still out of the dash) and turn the dash dimmer all the way up (full brightness) to pull as much power as possible (and to not heat up the rheostat) and after a few minutes turn everything off and carefully (very carefully - something that melts plastic will burn skin) feel the wires / connector / switch to see if it's getting hot again. If so, you probably have to get new connectors. Or you can add in power relays to control the headlights and the parking lights like Dave suggested.

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We could analyze this all day, but Darren needs to buy a new switch AND a new harness plug. I have to believe someone sells a plug, if they sell the headlight switch.

This switch is designed to see lots of heat. Notice the ceramic embedded around the NiChrome dimmer wire. That sucker gets HOT.

All the dash light current goes through it, and the more dash lights you add, the hotter it gets. Great resistor-technology, eh?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim_McNally</div><div class="ubbcode-body">Biggest problem with solder in a car is manufacturing cost and cracking due to vibration.</div></div> American cars don't use lead solder for electrical connections except maybe on some battery posts.

Solderless CRIMP connectors are unsurpassed for the best electrical connections. Yes, they even beat soldering by far.

The good ones are sleeves of copper, with a silver plating, enveloped in plastic or vinyl. #16-14AWG Butt Connectors are blue,

and #12-10AWG are yellow. Strip your copper wires, enter each end all the way in, and crimp them HARD to get a connection,

that makes the whole thing one copper piece.

It’s obvious to me that 20-amps running continuously through those steel connectors created enough heat to melt the plastic

without blowing the fuse. #12 class-2 copper wire safely carries 20-amps in free air. Oh, oh. We don’t have free air (and we

probably have #14 or 16-gauge wire). These steel connectors are held captive in a plastic shell with a hot switch behind it

and no air flow.

Darrin, if you can't find a new plastic plug, you can crimp wires onto new lugs and press them into the switch stabs. If you need

longer lengths, make short pigtails with Butt-Connectors using #12 THHN wire (available at Home Depot).

Here's your resistance table. Sorry I had to spell everything out. This forum doesn't do symbols.

Metal Resistivity (Ohms/m) at 20 °C

Silver ------ 1.59 x 10 to the -8th power =0.000000159 ohms

Copper ---- 1.72 x 10 to the -8

Gold ------- 2.44 x 10 to the -8

Aluminum - 2.82 x 10 to the -8

Tungsten -- 5.60 x 10 to the -8

Zinc ------- 5.96 x 10 to the -8

Nickel ----- 6.99 x 10 to the -8

Brass ------- 0.8 x 10 to the -7

Iron -------- 1.0 x 10 to the -7

Tin --------- 1.09 x 10 to the -7

Platinum -- 1.1 x 10 to the -7

Lead ------- 2.2 x 10 to the -7 = 0.0000022 ohms per meter

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Your parts are very common. If you can't find your switch and plug under TC, here's a list of other cars they fit:


1991 - 1993 LEBARON

1990 - 1993 IMPERIAL


1989 - 1991 TC MASERATI

1988 - 1992 NEW YORKER


1984 - 1987 TOWN & COUNTRY


1983 - 1988 FIFTH AVENUE

1983 - 1986 NEW YORKER


1983 - 1984 E CLASS

1981 - 1983 IMPERIAL

1977 - 1983 LEBARON


1975 - 1981 CORDOBA


1995 - 1999 NEON

1992 - 1996 VIPER

1989 - 1993 DYNASTY

1989 - 1992 SPIRIT


1987 - 1996 DAKOTA

1987 - 1994 SHADOW

1987 - 1990 OMNI

1986 - 1989 W100 PICKUP

1986 - 1989 D100 PICKUP

1985 - 1989 DIPLOMAT

1984 - 1987 ROYAL MINI RAM

1984 - 1987 MINI RAM

1984 - 1987 CARAVAN

1983 600

1983 400

1983 - 1989 ARIES

1982 - 1984 RAMPAGE

1981 - 1993 W350 PICKUP

1981 - 1993 W250 PICKUP

1981 - 1993 D350 PICKUP

1981 - 1993 D250 PICKUP

1981 - 1987 B350 VAN

1981 - 1987 B250 VAN

1981 - 1987 B150 VAN

1980 RD200 PICKUP

1979 RD200

1979 D100 PICKUP

1979 - 1993 W150 PICKUP

1979 - 1993 RAMCHARGER

1979 - 1993 D150 PICKUP

1979 - 1981 D450 PICKUP

1979 - 1981 D400 PICKUP

1979 - 1980 W300 PICKUP

1979 - 1980 W200 PICKUP

1979 - 1980 D300 PICKUP

1979 - 1980 D200 PICKUP

1979 - 1980 B300 VAN

1979 - 1980 B200 VAN

1979 - 1980 B100 VAN




1992 - 1993 CHEROKEE


1995 - 1999 NEON

1990 - 1992 ACCLAIM


1987 - 1994 SUNDANCE

1987 - 1990 HORIZON

1985 - 1989 GRAN FURY

1984 - 1985 VOYAGER

1983 - 1987 RELIANT

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  • 2 weeks later...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vicsik1969</div><div class="ubbcode-body">...I want opinions on whether you concur its a bad switch causing the problems, to include the partially melted harness, or some other bigger

electrical issue with the switch and harness being secondary effects...</div></div> I determined that excessive current was the cause. With that, please tell us how/why you are loading your light circuits.

Are you powering 'extra' things on your lights? Did you replace everything that was cooked? - Dave

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