my 99 ram has a dim drivers headlight so i cut into the ground wire coming out of light socket and grounded it to the body and it brightened up but will also stay on with light switch off i cant win any ideas? thank you
Both SnoMan and Fred may be right. Check the ground connection to the switch. If that connection is good, suspect the switch. Where ever the problem is, expect that connection/device to be getting really hot.
ONLY one way to know where your problem is. Use a voltmeter. Check voltage from "power" wire to battery power, and from "ground" wire to battery ground with lights on. Ground to ground should be 1/10 volt or less.Positive to positive likewize. f not, trace back to where it is. Bad connection will be between the point where voltage was high and where it was low.
Actually, you are the one who is incorrect. If you read what he wrote, you will see that he is telling the OP how to look for voltage drops. A bad connection will cause a voltage drop at that point which will be seen with the method that he gave.
Actually, no. You can still get correct voltage readings, but that does not mean enough current will flow through that weak point to supply the proper amount of "current" that item requires. He may indeed find a bad connection which may be "open" hence the improper or no reading. I speak from experience in voltage through a device/wire/cable will not always supply the appropriate current to operate a device. For example, connect a small gauge wire (not cable) to your starter in place of the standard gauge. You will find voltage when checking for voltage only. But as soon as the demand for current is needed, that wire can't supply the needed capacity. Fire hose vs. garden hose. I'd suspect "bad" connections rather than "open" connections.
Once again, if you read it you will see that you are incorrect. In order to perform the checks required, the lights have to be operating and if the lights are operating, any voltage drops (the only thing that can limit the current) can be discovered by his method.
You cannot get correct voltage readings if the required current is being restricted. This is made obvious by Ohms Law. The only way the "weak" spot can reduce the current would be by dropping voltage due to resistance and that would be detected by the suggested method.
If the connection were open, the light would not light at all.
While this is true, a voltage drop would be seen on the undersized wire and I have been doing this for over 30 years.
But this does not duplicate the method suggested as the starter is not operating as the headlights would need to be to perform this test.
And if you were to then measure the voltage at the starter, you would see a massive voltage drop due to the higher internal resistance of that thin wire which is exactly what the suggested method is looking for. Not so much a massive drop as in your example, but a significant drop due to a bad connection somewhere.
Of course it is a bad connection since the light does work, it is just dim.
No there is not. He has a simple series circuit. We are reading VOLTAGE DROPS. positive of lamp to positive of battery. Negative of lamp to negative of battery.If there is no resistance, he will not read any voltage. Also, reading positive of lamp to battery negative or negative of lamp to battery positive WITH LAMP ON there WILL be a lower voltage at the lamp if there is resistance in the circuit. You jhust have to know how to use the meter - which is what I was attempting to explain. I've done this for a living since 1969.
No, Laslo - you are WRONG. If you know anything about DC electricity you would understand. And we were looking for bad connections, not opens. We are testing UNDER LOAD - so we WILL find that piece of garden hose spliced into the fire hose.
As far as your starter example, check the voltage at the starter with it cranking. You WILL see a reduced voltage.
We are aware that he wants a fix which is why we are using a lesson in circuits and ohms law to help him find the problem and get past incorrect information that will hinder his efforts. It becomes much more difficult to diagnose a problem when attempting to diagnose with no knowledge at all.
Dang, I gotta agree with you for the most part. There will be a voltage drop somewhere as long as current is being drawn. The OP did say the headlight was dim which would indicate current. If the headlight were dead then it's very likely the voltage would read the same even if there were a resistance somewhere in the circuit.
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