torean

ok..this is the second headlight switch I've managed to burn up within the last 6 month.....some info about the car:

88t2 with silverrotors FD alt, regular stereo (200w) with regular speakers....nothing unusual so to speak, having problems getting the idle to come down below 1500rpm; I got the FD alt thinking I'd go towards an efan..but laziness and lack of $$ I've decided to stayed with the mechanical fan clutch....the problem is....the alt is too powerful for the car...every morning when i start up the car the voltage reads 14.7+ (readings gotten from an apexi turbo timer tapped into the ecu harness) i know this is wayy too high to be normal, however after some driving the voltage will drop to 14.4 and stay pretty consistant around that number..however i've seen the meter read as high as 15.2 some mornings...i try to drain the system by blasting the cabin fan, turn on head lights......now the problem is the headlight switch failed

the problem at first was after i turn off the switch the parking light would still be on...after some heavy tapping it turned off..but now when i turn on the switch the parking lights wont turn. driving lights still work, just the parkings

I've gotten another switch from a friend but would like to know what is the source of these failures. before I burn up another switch. I've taken out the switch tonight and noticed that one of the plugs on both the connector and the switch are burnt.. can anyone varify if the burnt plug is the 12V source?..

86rx7racer

change out the alternator then. i have a s5 alternator for sale for $50 + shipping if you want

torean

nahh....i would prefer to stick to the FD alt...cause i know the problem im having isnt common...i havent heard of any other ppl having problem with silverrotor's alt

Icemark

I have covered quite a few times why the headlight switches burn out.

Did you replace the headlight switch harness at the same time as the switch?

The most common reason for the headlight switch to fail is that the parking light bulbs have not been maintained. In many of the bulb sockets you may find corrosion. This increases the load on the switch and over heats the connections at the switch (burning up both the headlight switch and the headlight switch harness. Never ever ever re-use a damaged headlight switch harness as once the connections have been burnt, they will increase the resistance and cause the failure all over again. Bulbs (when ever replaced or corrosion is found in the sockets) should have a coating of conductive grease when installed to prevent the corrosion from being and issue.

Also any additional lights on the parking lights circuit can cause the switch to overheat and burn out. Always use a relay for any additional lights.

The third reason for failure is a cold solder joint in the switch (but this really only happens about 10% of the time). This cold solder joint happens where the pin meets the circuit board and will again cause the same problems.

I do have rebuilt headlight switches available on my webstore as well as a relay kit for increasing the load and protecting the headlight switch from being overheated and overloaded. But you do need to fix the bulb sockets and headlight switch harness before using either.

Carzy Driver

Icemark needs to chime in..


edit:^^^^^^^^ he's here

rxspeed87

not suer if I follow. how does increased resistance mean more of a load and more current?

Icemark

Bad bulb sockets (or the rare broken solder joint in switch) = increased resistance

increased resistance = heat on contact surfaces.

Heat = more amps required to light the same lights, because some are getting wasted in the heat

heat = burnt plug at the weakest connection

Fuse doesn't blow because the amperage draw does not exceed the 110% of the fuse rating (a 7.5 amp fuse blows at 8.25 amps being run through it).

rxspeed87

guess that makes sense. as I admit I am not the greatest at electronics. I have seen with some of the amps I have built that the lower I have the resistance for the device the higher the temps as more current si flowing I thought but then again I admit I'm not the greatest with the electronics but you can at least see where I'm comming from I hope.

Icemark

Higher temps actually would indicate more resistance or less efficency in all electronics.

rxspeed87

I can understand what your saying it's just not clicking for some reason. though thank you for being helpfull. for instance though if you take a straight wire and run it from + to - on a 12v batt the wire gets very hot the batt gets hot and so forth. if you take a 4.7k ohm resistor and do the same though the resistor stays cool the batt stays cool. can you explain that?

and don't worry about making me feel like a moron I'm doing a good job of taht on my own right now as I have built this stuff and still don't understand something smple like this. but then again I never thought about it has most things I have built I never have had to worry about heat. the hottest things I have built are tube preamps but even then I usually haven't had any heat related problems.

stylEmon

iTrader: (2)

IceMark, I followed your tutorial on adding a 30A relay on the light switch, It was really easy to follow and only took about 1 hour. I burnt out 3 switches/harnesses before I installed the relay. Since the install, its still going strong.

Icemark

Good to hear!

It really takes a load off the switch. Mazda should have really used an outboard relay for the parking lights, just like they did for the headlights.

Icemark

Because more current is running through the wire than the wire can support. If you had a big enough wire (and a power source stable enough not to explode) you would have limited heat.

Yes I used to help build and design deHavilland Tube amps myself when I was with the company when it was in Northern CA.

But in those cases you are delibertly heating to change the sound reproduction (often by adding distortion because of the heat).

But lets use a tube amp as an example... If you used a 28 awg wire for the your power supply to pre-amp stage, what would happen. Would the wire get hot. Yep

But if you used a 14 AWG wire, would the same thing happen??? probably not.

So in closer to automotive standards, lets say we put that amp in the car, and ran a wire to the battery to power it. What would be better the 28 AWG wire or the 14 awg?

Well every connection, every joint can be a reduction in gauge (particularly if there is corrosion in the joint), so now to use that same example of a amp in the car... if we had a 14 awg wire running to the amp, but at the battery we cut the wire down to a 28 awg before the fuse... what is gonna happen at that 28 awg wire. Its going to get hot.

rxspeed87

makes a little more sense. thank you icemark

Pele

iTrader: (28)

Bumping this because I have the same problem...

I am rebuilding the headlight switch with the same relay I used in the wiper switch.
My problem is, Malloy Mazda wants $110 for the headlight switch harness. That's about half of what I paid for the car.

If I add the relay per Icemark's instructions, do I really need to replace that harness?

Raid3n

just find a car at a junker and crawl under the dash. you don't necessarily need a new one, just one that isn't crispy.

HAILERS

It depends on what the instructions say. I've never seen them.

I wouldn't have used the wiper relay but would have bought a common auto relay from Radio Shack and used that. Actually I had this problem on one car and just installed a switch for the side/tail lights....but shoulda gone the relay way instead, since the person who is going to do my state inspection is going to want to know why my side/tail lights don't come on.

stylEmon

iTrader: (2)

I went to the junk yard and pulled a couple of those headlight harnesses. They all worked fine.
As stated above, just make sure they arent already burnt out.

Once you put the relay in, it's much easier on the old wiring.

Pele

iTrader: (28)

Take apart the Headlight switch and there's an exact same relay like inside the wiper switch... Since I had a stack of new ones from Digikey for rebuilding wiper switches, I replaced it.