QuestionQUESTION: Hi;
A few weeks ago I had smoke from the LH (UK passenger) side glove box; the bulky grey connector was v hot; investigation revealed that brake lights were earthed via the rear side light bulb and the brake switch was melted and distorted. New brake switch fitted and the earth snipped. No more hot connectors. Then the radio (fed off courtesy light supply) started to turn itself off after approx 20 seconds but comes back on a few hours later; hazard lights behave similarly but inconsistently...
At times when the radio won't work, flashing the headlights (and holding the flash on) seems to turn the radio on. At times when the radio is working, flashing the lights sometimes knocks the radio off.
And finally the main light switch has two hot wires - a brown and a blue and a red/green that doesnt get hot (side light feed i think). this switch has been re-built a few times as it occasionally fails to work (springs a bit bent).
Appreciate that the above is quite random, and I'm not an electrician but have a voltmeter and have checked a few voltages etc.
Any advice would be appreciated.
Thank you
ANSWER: Hi Andy,
I learned that when working on an electrical problem the symptoms can lead you to an area, but testing is the only way to find a problem.
You need to take a wiring diagram of your car and a test light and pick ONLY ONE circuit of all your problem circuits and trace that circuit from one end to the other. In doing so you have to locate the problem with that one circuit. This may lead you to all the problems but ONLY work on one circuit at a time.
If you don't have a diagram let me know and I will put one on my web site for you to copy.
Howard
---------- FOLLOW-UP ----------
QUESTION: Thanks Howard; I guess i need the dash off and may have to start unravelling looms. Just one qn - what should the voltage drop be over the main light switch - it reads 11.8v on the brown wire and 11.3v on the blue; is this ok or does it indicate a faulty switch?
Thanks again.
AnswerHi Andy,
A .5 v voltage drop across a switch is not enough to condemn the switch as you may test it several times turning the switch on and off several times to see if it changes and keep in mind that the blue wire (head lights) is sharing the output with parking and dash lights so the load is distributed to several circuits inside the switch and thus lowering the voltage available to the headlight wire (Blue)
I would try to clean all the connectors in the gray plug that you found hot and heat is a sign of high resistance and is also a point of poorest connection. When you get a short in any wire the weakest point will get hot. That is the reason for fuses as they were designed to be the weakest point and when you get a short, they should be the weakest link and thus burn. I don't understand why your fuse did not blow. It sounds like the car has some wires connected up wrong as that circuit should have been fused. Unless some one has put a very high amp fuse in the fuse block.
You need to trace that circuit to see where it receives it's power. It sounds to me that it has been connected to a direct power source without a fuse.
Howard
