I have a Pontiac Sunfire 2005 model. Around February this year I noticed my headlights were a little low. I thought I was developing cataracts or something, but my friends seem to notice it too. I haven’t been doing much driving at night but the days are getting shorter and I’m noticing it more and more. I changed out the H11 low beam bulbs which made it worse! It is supposed to deliver 55W at 12V. I checked the voltage and I have 11Vdc. Is this little bit enough to significantly reduce the light? What might be wrong here?
Precisely how did you measure 11 volts? Exactly where were your meter leads?
I’d expect to see a full 12 plus volts at the headlights, and this may well be your problem.
I disconnected one bulb and measured on the plug which inserts into the bulb. I left the other bulb connected.
Have you looked at the lenses of the headlights? I know it seems to be a common occurrence where the plastic lenses of the headlights cloud up, dimming the light output
lenses are not fogged up. Is there some other device between the battery and the light bulb; like a ballast? I was thinking that either the battery is not supplying the correct voltage, or if the ballast exists there might be issues with it.
The 11 volts indicates there’s a voltage drop to the headlights. The first thing to check is the headlight relay. If the contacts in the relay are erroded/burned it can cause a voltage drop to the headlights.
There’s no ballast in your system. It’s a wiring / switch problem. You should have 12 volts on that socket with the engine off and 13 volts with the engine running. Check the voltage at the battery. The voltage at the socket should be down no more than .5 volts. You may have a bad connection, a bad switch, a bad circuit breaker that protects the headlight circuit.