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Car Forum / Ford / Ford Trucks / May 2007Both low beam headlights out
Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned that one of his headlights was out. Upon observing, I noted that both low beams were out. I removed one headlight bulb and sure enough, one of the filiments is broken. My son swears that he had one low beam working just the night before. I suspect a wiring problem since the odds of BOTH low beams failing within 24 hours are very high. However, both of the high beams work ok. That leads me to believe that maybe the wiring and switch is ok. Turn signals, stop lights and parking lights work ok. If I replace both headlight bulbs and both of the low beam filiments blow, where should I start looking as to a short circuit? By the way, I checked the fuse box under the hood and could not find any headlight relay. Is there one? Does the Ford have a built in circuit breaker in the headlight switch as do most other vehicles? > Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned > that one of his headlights was out. Upon observing, I noted that both low [quoted text clipped - 9 lines] > there one? Does the Ford have a built in circuit breaker in the headlight > switch as do most other vehicles? It happens. I had a '70 Plymouth Satellite once that had four headlights (two high beams, two low beams, but the lows also had another filament that ran on high). Anyway, one night I noticed I had no low beams, but the highs were ok. I assumed it was a wiring problem and spent an afternoon troubleshooting. I was ready to give up when my father-in-law mentioned the bulbs were probably bad. Didn't believe it, but bought two new low beams, installed and everything worked again. RCE It is odd that both woulld fail at the same time, but it can happen. Put new bulbs in and drive happy ... The Low Beams are separate from the other stuff you listed. Replace the lamps and you should be okay ... >It is odd that both woulld fail at the same time, but it can happen. Put new >bulbs in and drive happy ... If they all failed like that I would do a voltage check on truck because if you have high voltage from a bad regulatorin alternator it can shorten headlight life a lot!!! ----------------- TheSnoMan.com >>It is odd that both woulld fail at the same time, but it can happen. Put >>new [quoted text clipped - 3 lines] > because if you have high voltage from a bad regulatorin alternator it > can shorten headlight life a lot!!! Only the Low Beams have failed, and there are only two of them. I would not suspect a voltage regulator at this time. Replace the bulbs and drive happy ... PS You should learn how to reply to the person you are actually talking to. >Only the Low Beams have failed, and there are only two of them. I would not >suspect a voltage regulator at this time. That depends because low beams are used the most and would suffer first from over voltage. It only takes a few seconds to check voltage. ----------------- TheSnoMan.com >>Only the Low Beams have failed, and there are only two of them. I would >>not >>suspect a voltage regulator at this time. > > That depends because low beams are used the most and would suffer > first from over voltage. It only takes a few seconds to check voltage. Okay. I would not waste my time or suggest that anybody else waste theirs. I suspect that one headlamp simply failed due to age, and the operator either failed to notice, or did notice but took no action. After an unknown period of time, the other lamp failed due to age. PS Anytime the low beams are on, all of the other lamps are also on, so to suggest that the low beams are used more is inaccurate. They are used more than the high beams, that much is true. There's nothing that can be wrong with the wiring that would cause a headlamp to "blow". And why wouldn't they burn out about the same time? Just replace them and don't touch them with your fingers.  SignatureSteve Barker > Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned > that one of his headlights was out. Upon observing, I noted that both low [quoted text clipped - 9 lines] > there one? Does the Ford have a built in circuit breaker in the headlight > switch as do most other vehicles? > Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned > that one of his headlights was out. Upon observing, I noted that both low > beams were out. I removed one headlight bulb and sure enough, one of the > filiments is broken. My son swears that he had one low beam working just > the night before. I suspect a wiring problem since the odds of BOTH low > beams failing within 24 hours are very high. Don't make it so complicated. If there was a wiring problem, for the most part you'd see reduced voltage, and the lights would last forever. Odds are it's just that the first light burned out 2 years ago, and you're just now finding it out. If there is a problem it's that the system voltage is running too high. You can easily check that with a volt meter. >Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned that >one of his headlights was out. Upon observing, I noted that both low beams [quoted text clipped - 9 lines] >the Ford have a built in circuit breaker in the headlight switch as do most >other vehicles? Replace just one , that way they both won't 'blow'. :-) You're worried about breaking the eggs before the chicken lays them. >Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned that >one of his headlights was out. Upon observing, I noted that both low beams [quoted text clipped - 9 lines] >the Ford have a built in circuit breaker in the headlight switch as do most >other vehicles? It is a quite normal occurance after one lamp fails. Once you have one lamp failed, the other will usually have a bit more voltage available which may accelerate it's demise. You may also consider headlamps have a rated life for a particular lamp series and type. They may both be in that range. That is why I always replace both sides if one failes. Now, if your son knew he only had one lamp, he should have been making PDQ arrangements to replace it. WTH would he do if the second had failed during night driving - blind the rest of us with his high beams?? Lugnut >>Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned >>that [quoted text clipped - 19 lines] > you have one lamp failed, the other will usually have a bit > more voltage available Say what!? My house has vlotage coming in from the nearest transformer. If I unplug EVERYTHING except for one night light, the light is still only going to get 110 and draw the amperage it requires. It will not get blasted with all of the voltage and current coming into the house. A motor vehicle works the same way -- the alternator produces whatever it produces, and any given load takes what it needs. If there are too many loads, then the voltage produced will drop, but there is no way that any given load will be over-supplied. What is normal is that two bulbs will have similar life spans and when one of them fails, the other one is not far behind. I always replace headlamps in pairs just for this reason. >>>Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned >>>that [quoted text clipped - 29 lines] > takes what it needs. If there are too many loads, then the voltage produced > will drop, but there is no way that any given load will be over-supplied. Not exactly. An automotive power system is a lot 'softer' than a large AC distribution system, meaning that it is more sensitive to load changes. Try this experiment: Put your analog voltmeter on the battery while the alternator is turning. Turn on all the electrical loads in the car...headlights and A/C blowers in particular. Have an assistant switch off the loads. As each one is switched off, you will see the voltmeter needle jump up, and then settle back. (A cheap Radio Shack digital voltmeter will likely not respond quickly enough to show this). The alternator voltage regulator does not respond instantaneously to a change in load. Any electrical circuit (even a piece of wire) will have some small amount of inductance. Voltage across an inductance is equal to the inductance multiplied by the time rate of change of the current through the circuit. ( V = L * di/dt). Turning a circuit on or off causes the current to change rapidly in a short time (therefore di/dt is large). Not quite sure what you meant by: > It will not get blasted with all of > the voltage and current coming into the house. All of the circuits are in parallel, therefore they all see the same voltage that comes into the house, no matter how many are turned on or off. But as things are turned on and off, the exact same phemomenon as described above (switching transients) are also generated in your house. I sometimes explain electricity to people who don't understand it as follows: Think of the conductor as a water hose. The voltage is the pressure in the hose, and the water flow is the current. If you switch off the nozzle, the pressure (voltage) is present in the hose, but no water (current) is flowing. SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 16 days 9:19 >>>>Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned >>>>that [quoted text clipped - 73 lines] > nozzle, the pressure (voltage) is present in the hose, but no water > (current) is flowing. I know all of that. My analogy still holds true. The time it takes for the automotive system to adjust itself is not long enough hurt anything. >>> Say what!? >>> [quoted text clipped - 51 lines] > My analogy still holds true. The time it takes for the automotive system to > adjust itself is not long enough hurt anything. Although it's not likely that transients burned out the OP's headlights, your AC distribution analogy still has some problems, or maybe you don't have a good understanding of basic electrical circuits. In fact, the circuits in your house will 'get blasted with all of the voltage' (to use your words), since they are parallel circuits. As I stated before, an AC distribution system (at least in the US) is usually pretty stiff, meaning the voltage changes very little with load changes. In other countries, especially developing countries, this is not always the case. In a place that I worked (not in this country) a couple of years ago, the local AC system was so soft that there was not enough fault current available to trip even a relatively small circuit breaker in the presence of a conductor-to-ground fault (the voltage dropped instead). SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled >>>> Say what!? >>>> [quoted text clipped - 74 lines] > breaker in the presence of a conductor-to-ground fault (the voltage > dropped instead). Automotive systems are also parallel circuits. You are splitting hairs. There is never a problem with one headlamp getting "too much power" because the other one has burned out. I get that my analogy is not accurate for every instance, but it is more than adequate for the topic that is being discussed by everybody but you. >>>>> Say what!? >>>>> [quoted text clipped - 76 lines] > > Automotive systems are also parallel circuits. Yes, they most certainly are. > You are splitting hairs. There is never a problem with one headlamp getting > "too much power" because the other one has burned out. Never said that. In fact I said that it is not likely. > I get that my analogy is not accurate for every instance, but it is more > than adequate for the topic that is being discussed by everybody but you. What I was pointing out was that you were not accurate when you said that all of the circuits wouldn't see the same voltage. They will. Maybe that's not what you meant, but that's what you wrote: > It will not get blasted with all of the voltage... SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 10:36 1 user |
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