Reply to: RE>Re: Puzzle from Joe Lucas
Roy Wang writes:
(Asbestos suit on.)
This may be a totally stupid suggestion, but if the right and left
blinker have diffrent connections or seperate blinkers, you might want
to check the voltages going into the flasher unit. I haven't studied
how a flasher exactly works, but I'd bet a lower voltage would probably
slow down a blink.
(Asbestos suit off.)
Am I totally off on this?
**** Not totally. Thermal blinkers *are* highly voltage sensitive. But the
common setup is to have one blinker for the whole car. Thermal blinkers are
also highly *LOAD* sensitive, though. The more current that is sucked through
them, the faster they blink. This is because the bimetallic strip heats up
faster. Slow blinking on one side is usually caused by bad connections, or
having the wrong bulb, or having one of the two bulbs ( front & rear ) burned
out. It would be educational to measure the voltage at various spots on the
slow side. Use an analogue meter type intstrument, or, even better, an
oscilloscope. Measure the voltage right at the flasher WHILE ITS BLINKING.
Then measure the voltage at the *hot* side of the bulb. Is it much lower? Is
it more lower than the voltage on the "good" side? BTW, these measurements
mean the most, if you always reference them to the same point, I.e., the ground
post of the battery. After all, that's where the current is coming from. So
you should make up at least one really long lead for your meter. Such a setup
can also be used to tell you about grounding problems. Is there voltage at the
ground terminal of the slow-blinking-light? If so, you somehow have a bad
connection on the ground side. Commonly caused by corrosion at the connector,
but can also be caused by corrosion between the fender and the rest of the
body, or the interface between some other body parts. In general, I have
always felt that depending on the car body for a ground sucks.
Sticking an ammeter in the blinker lead can help, too, but that's pretty
intrusive, since you have to break the circuit.
Does your blinker have screw connections? If so, you can switch right and
left, and see if the problem switches too. It probably will. At any rate,
once you eliminate the wrong/bad/burned-out lightbulb problems, you need to
focus on bad connections. Where the large voltage drops ( differences ) are,
there also is your problem! The meter with the long lead comes in handy here
too. Just hook it between the plus terminal of the flashing light, and the
flash-output terminal of the flasher. Even while flashing, you should see no
voltage, or very little voltage here. After all, the two points are ostensibly
connected by the wiring of the car. Another common problem with flasher
systems is the steering-column switch. This can develop high resistance. Hope
this all helps.
- Jerry
p.s. Turn signal problems can easily be attacked like troubleshooting a
stereo: You have one good channel, and one bad channel. You can discover a
lot by comparing readings from the good & bad sides.
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