Dim/Dipped Headlights keep blowing
#1
08-24-2009 | 05:12 AM
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Dim/Dipped Headlights keep blowing
The dip/dim headlights of my Mazda 323F are not working. I previously changed bulbs and they only worked for a short period of time. Now I have changed bulbs and they are not working. I have checked fuses and they are also working. Any ideas?
#3
09-07-2009 | 07:14 AM
Senior Member
Joined: Mar 2009
Posts: 466
You wrote: "Now I have changed bulbs and they are not working."
Do you mean they behave the same way as the ones you replaced, or they don;t come on at all?
This is a weird problem, but I can suggest a number of things to check.
(i) Drive the car for about 20 minutes to ensure the battery is fully charged, Run the engine at fast idle, and measure the voltage between the +ve battery terminal and the car chassis up front near the radiator. That voltage should measure no more than 15 volts maximum, ideally, 14 volts; if it's higher, you have a problem with the car's electrics.
It could be poor main chassis grounds, poor connections on the +ve side wiring between the battery and the alternator, a defective regulator in the alternator, or a defective battery. A persistent overvoltage of just 5% cuts bulb life in half.
(ii) The other problems are mechanical. The heat from the bulb is conducted away by the bulb mounting flanges, so even though they don't carry any current, the surfaces where the bulb is in contact with the headlight assembly still need to be smooth and clean, or else the bulb will overheat, cracking the seal where the filament contacts exit the bulb. The protective shrouds in the headlight assembly area are also important, a single drop of water getting into the area and finding its way to the bulb flange will cause the bulb to seal to crack instantly.
Finally, when you handle those bulbs, don't touch the glass envelope. Even invisible fingermarks can result in glass stress and failure. Use a tissue when handling bulbs, and in case of accidental contact, use a tissue wetted with alcohol to clean the bulb.
When you are finished be sure the bulb retainer is clean and is turned fully to the locked position, otherwise the contact pressure won't be enough to ensure proper heat conduction.
Do you mean they behave the same way as the ones you replaced, or they don;t come on at all?
This is a weird problem, but I can suggest a number of things to check.
(i) Drive the car for about 20 minutes to ensure the battery is fully charged, Run the engine at fast idle, and measure the voltage between the +ve battery terminal and the car chassis up front near the radiator. That voltage should measure no more than 15 volts maximum, ideally, 14 volts; if it's higher, you have a problem with the car's electrics.
It could be poor main chassis grounds, poor connections on the +ve side wiring between the battery and the alternator, a defective regulator in the alternator, or a defective battery. A persistent overvoltage of just 5% cuts bulb life in half.
(ii) The other problems are mechanical. The heat from the bulb is conducted away by the bulb mounting flanges, so even though they don't carry any current, the surfaces where the bulb is in contact with the headlight assembly still need to be smooth and clean, or else the bulb will overheat, cracking the seal where the filament contacts exit the bulb. The protective shrouds in the headlight assembly area are also important, a single drop of water getting into the area and finding its way to the bulb flange will cause the bulb to seal to crack instantly.
Finally, when you handle those bulbs, don't touch the glass envelope. Even invisible fingermarks can result in glass stress and failure. Use a tissue when handling bulbs, and in case of accidental contact, use a tissue wetted with alcohol to clean the bulb.
When you are finished be sure the bulb retainer is clean and is turned fully to the locked position, otherwise the contact pressure won't be enough to ensure proper heat conduction.
Last edited by oldeng; 09-07-2009 at 07:15 AM. Reason: Forget (ii) at intro to mechanical issues.
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