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I don't understand left turn signal and front headlight problem?

Recently, when I used the left turn signal, my flasher in dashboard would go fast. I checked outside and the front signal bulb was out and the rear left signal was blinking fast. I replaced the front bulb thinking that the rear would go back to normal. Not so. I plan to replace the rear turn signal tomorrow. I also noticed that when I have the headlights on, the front turn signal does not work. Can anyone explain why turn signal would be affected by headlights? Are they not separate bulbs, relays, and switches? I don’t understand the connection. I hope changing rear turn signal stops this! any suggestions???

When asking a vehicle question, always provide the make, model, and year.


Sorry for not mentioning make of car! It’s a Honda Accord 2002 Ex.

Can you actually see a defect with the bulb you did replace/ This defect could be inside the bulb or outside. Is the bulb type used the type that has two exposed wires for contacts? If yes this buld type can result in a damaged socket also.

I can not explain the connection to the headlight, lets hear the results to the bulb type questions.

Changing the rear bulb won’t help the situation because it is ok. The trouble is with the front one. You said you replaced it so there is either a bad connection to power to the socket or the ground side is bad and not making connection for some reason. Since the front signal doesn’t work when the headlights are on this would indicate a bad ground connection for the lights. Try cleaning the grounds to the chassis under the hood. It may clear both problems.

I threw the bulb away. Honestly, I am new to cars so it did not occur to me to check socket or ground. I recall the bulb have 2 exposed wires. I will check socket tomorrow but what does a bad socket look like?

hey cougar, you don’t think changing the rear turn signal (the really fast blinker) may take some load off the front turn signal? I 'm also hoping that the flasher in the dashboard will go back to normal! That’s one issue…next problem is the no front left turn signal when headlights (and all the back lights that come on when you turn on headlights) are on. I plan to check if turn signal doesn’t come on if i just put parking lights on?

You suggest a bad ground connection for the lights. I am new to all this so what exactly does bad ground connection for the lights (which lights: headlights or turn signal lights)mean? bad wiring??? how does one clean the grounds to the chassis under the hood?

since it’s late already and I cant get the parts I want right now, i keep driving myself crazy with possible answers…I was wondering in my honda accord 2002, to the left of steering wheel is this lever (???). lever does many things. (1) push up/down its the turn signals;
(2) if you turn once, parking lights; (3) if you turn again, headlights and whatever lights come on with the headlights; (4) also does highbeams. this level does not control hazardous lights and it works fine. I was thinking this lever does all this must be connected to some switch or relay…maybe my level is malfunctioning? just a suggestion

what do you guys/gals think? thanks so much for any advise!!!

You seem to be describing a problem with the grounding at the left headlight/turn signal/parking light assembly. Changing the rear bulb certainly won’t fix that.

The turn signal flasher is pulsing at a fast rate because the left front bulb isn’t working. This will happen anytime one of the bulbs isn’t working. The rear bulb has a normal load resistance, it works. The flasher will go back to normal flash rate when all the bulbs are working as they should be.

As far as grounding is concerned. The negative side of the battery ties to the engine and chassis of the car. That is refered to as ground for the electrical systems of the car and provides the return circuit path to the battery for all the electricals. There are a number of wires tied to the chassis to bond the areas to a good ground connection. The area for the headlights has a bad connection since you say the turn signal doesn’t work when the headlights are on. When the headlights are on they are causing a voltage drop to occur across the ground to them due to a bad connection which causes a voltage drop to occur when current passes though a resistance. The voltage drop on the ground will cause the smaller lights to not work since they are a higher resistance than the headlights, which draw much more current than the marker lights do. This all has to do with Ohm’s Law but we won’t get into that here.

Since you brought up the emergency flashers it would be interesting to know if the left front light works ok with that switch on. If it does then the turn signal problem is most likely with that switch and not a ground problem for that light. Try cycling the switch a number of times to see if that helps clear the trouble. The headlight issue is a ground problem though. Check the ground connection between the negative battery connection and the chassis. Try cleaning the connection to the chassis.

Hey cougar thanks for your reply!!! I just went out to my car and i checked the front turn signal and it’s dim even though i put in new bulb. I plan to check the socket since i did not do that. I also checked the emergency flashers and you know what, the left turn signal is dim. Since you mention battery, I’m assuming you mean car battery? Recently my battery has stalled on me. My volts were good but CCA was very low. I was planning to replace the battery today! Do you think having a bad battery could also play into dim turn signal?

The common component with the turn signals and headlights is the combination light switch in the steering column. If there’s a short in this switch, it can cause the problems you describe.


Since the light is dim for both modes the trouble appears to be a bad ground to the light. The extra resistance to ground causes less current to flow through the light so it is dim. The trouble could also be with the hot side of the light but I would suspect the ground side first.

Before you replace the battery I suggest you have the charging system checked out first to make sure it is ok. Have a load test done on the system. It will show what really needs to be done. A low battery won’t cause the trouble with the lights you are having. You need to check the grounding like I stated earlier. If you don’t know what to do I suggest you have a shop check it out.

thanks guys!!! I’m going to check the grounding tonight to see if that’s it. If it’s not that then I will have someone check out the combination light switch. I was wondering since the side marker light is the same as the turn signal bulb and the side marker light comes on with the headlights, could another solution be the flasher relay? what is the flasher relay? what does it do?

I would not rule out that rear lamp yet. If it is a combo lamp both turn/brake and tail light in one, then it could be the problem.

is the combination headlight switch and turn signal the same as the lever that controls the wipers, headlights, and turn signal? the lever that is left of the steering wheel?

As the name implies the flasher is what makes the turn signals blink. It could be causing the trouble but I doubt it is the problem.

Yes, that is the combination switch. It ties to a combination of things.

Tester may be correct about the problem being in the combination switch but I have my doubts that it is the cause since the emergency flashers have the same problem. The ground connection is another common thing for the light. One simple way to prove it is to tie the ground side of the faulty light to a jumper tied to a good ground point.

As always a complete understanding of how the exact system is supposed to work combined with a schematic and good troubleshooting skills is a sure bet to fix this.

Hello from 2019

I have the same problem, how to solve it?

I have changed the headlight and lever, but the problem still the same, plz help

what car brand, model and model year do you own? How many miles on it? If it’s an older car, the headlight socket might need to be replaced. I did that recently with the low beam headlight sockets on my wife’s 2009 Chevy Cobalt. I bought them off the display rack at a local parts chain store. I cut the wires from the socket, stripped the wires, slipped shrink tubing over the wires, and soldered them. I finally pulled the shring tubing over the bare wire and shrank it. The headlights have worked for the last five months.