Auto Repair Help
Carl’s Corner – Auto Repair Help

By Carl O’Reilly

The turn signals do not flash or they may flash in only one position or one side may remain on constantly with the switch in the off position.

The turn signals use a flasher unit that acts as a repetitive circuit breaker. This unit makes then breaks the electrical circuit that turns on the turn signal bulbs. The cycle will continue as long as the directional switch is turned on. This unit relies on heat build up caused by electrical current flow to determine when to break the circuit. When the switch is initially turned on, electrical current flows through the flasher unit to the bulbs. When this occurs, heat builds up in the flasher unit. When the heat reaches a predetermined temperature, a metal strip within the unit stretches due to the heat and breaks the electrical circuit turning the bulbs off. With the bulbs disconnected from the circuit, the flasher unit cools off. Once it has cooled, the metal strip re-contracts and re-closes the electrical circuit turning the bulbs back on. The usual cause of inoperative turn signals is a defective bulb or flasher unit.

Prior to performing extensive diagnosis, check the vehicles fuses to ensure they are not blown. Some vehicles utilize two fuse boxes, one in the passenger compartment and another under the hood. Consult your owner’s manual for fuse box locations and fuse ratings. If the directionals only flash in one position and are off constantly in the other direction, the usual cause is a burnt-out bulb. When a bulb blows, the current flow in that side of the circuit will be reduced. The reduction in current flow prevents the flasher unit from reaching the needed temperature to switch the bulbs off. Turn the directionals in the position where they are inoperative and perform a visual inspection of the exterior bulbs. Replace any bulbs that are not lit. The flasher unit is used to switch the current on and off for both right and left directionals. If the turn signals are inoperative in both directions, a defective flasher unit or blown fuse is the usual cause. On most vehicles the flasher unit is located on the front or on the back side of the fuse box located in the passenger compartment. Some vehicles use a solid state flasher module that contains transistors and diodes. On these vehicles, you should consult a vehicle specific service manual for proper diagnosis.

You should always use a replacement bulb of the same part number as the one being replaced. Your owner’s manual will indicate the correct bulbs for each location on the vehicle. Using the incorrect bulb can create too slow or rapid turn signal operation. Manufacturers often use grease to repel water from the bulb sockets. Do not remove this grease from the bulb socket when replacing defective bulbs.

69 Responses to “Diagnose The Turn Signals Dont Work Or Dont Work Properly”

  1. Tony Z says:

    What if the bulb is good the switch was replaced and still no signal lights. What else could be the problem?

    • Anna says:

      I have the same question. Bulb is still good as well as fuse. But still no signal or rear break light

      • artie says:

        I have a 1995 ford f-150 have no brake lights in rear of truck but do have brake light on back of cab of truck, no turn signal lights and no emergency flashing lights, replaced turn signal switch and brake bulbs and fuses and turn signal fuses and do have tail lights, PLEASE help me with out?!!

        • Da-Sarge says:

          With the F150 check the two electrical connectors uner the bed of the truck back by the rear bumper one is round and the other is a square shape these like to carrode rendering the rear lights inoperable also tge tail light sockets can be unplugged from the harness (careful with the clips on eather side of the sockets they like to brake) the tail lights on the 90s and early 2000s (up to current for f250 and higher) they tend to get water in the lights that kills sockets these are the usual causes of the problems if you loose all rear lights check the harness by the chasis in the front drivers side wheel well for chafeing (can also cause rear light loss) very commen on the 1996-2003 F150 all cab and trim types and bed types these are the commin areas to look for failures hope this helps you out

    • Hi,turn signals don’t flash, replace bulbs and flasher.some time they flash fast and slow, then stop flashing all together, but they turn on. Can you help please.

  2. wyatt mohring says:

    right turn signal flashes to fast

  3. shawn says:

    but in new turn signel swicht and have no taillight and blinnkers

  4. Sheila says:

    Signal lights not coming on but hazards do come on. Checked fuses. They seemed to be fine. Please advise. Thanks.

  5. Tommy says:

    Yes you are exactly right! Thank you so much! I changed the flasher and she works fine! $4.00 Thanks to your advice probably saved me up to $400 on mechanics which I’ve seen that many do blow smoke to steal your money. I was thinking I’d have to get someone to pull my steering wheel and change out the tumbler switches! God bless you!

  6. marx says:

    I replaced the flasher on a ford f 150 1998 but still dont work my turn signal stilk dont work

  7. John S says:

    I have a 1995 GMC 1500 4×4. My rear blinkers, brake lights and 4 way flashers do not work, But they all work in the front. My rear running lights work.
    I haves tested all the bulbs they are good, also tested the rear ground wire it is good. Could the problem be my relay under the hood? I am led to believe it controls both the blinkers and the brake lights?

  8. brian v says:

    I have a 76 cheyenne, and i have been having the same problem. My turn signals dont work. But brake light and hazards do i checked the fuses, new flasher, and replaced the turn signal switch but still nothing.

  9. chris w says:

    2006 CVPI no turn signals but when brakes are applied the switch will turn off brake light

  10. jonny says:

    both turn signals will begin rapid flashing, but if I turn the car off and on again both signals begin working perfectly fine.
    This has become more frequent for a few weeks now.
    Saturn ion 2005

    • Rick Vise says:

      I have a 1947 Ford car and installed a after market turn signal switch. The blinkers work great until I turn the headlights on then only the front blinkers work and the rear lights light up but do not blink. Also I have no brake lights. Checked all the fuses and grounds and they look fine. What should I be looking for to fix this problem?

  11. Steve says:

    Thanks just got new headlights the blinkers in front didn’t work I got new bulbs with them. Never expected them to be bad but thanks to you I rechecked bulbs and they were bad

  12. al says:

    hello, I just rewired a trailer correctly and the lights function properly. however, the right signal flashes a little fast (trailer connected or not)and the bulbs are flashing on the trailer,but the right blinker seems to to bleed a little into the left light on the trailer only, but not vice-versa. Now that’s strange. What do you think. Thank you.

  13. Gregg says:

    I have a problem I’ve never seen before or heard of. When I put either left or right blinker on ALL lights blink like my hazards are flashing with the turn signal.

    • sam mcginnis says:

      i have the same problem and wonder what has been found to correct it, changed the hazard switch already didn’t help, turn on turn signal and hazard light come on both left or right turn, hazard switch would just buzz before i changed it. thanks sam

  14. tracey-lynn kennedy says:

    just wondering my hazards light works but right and left single doesnt changed fuse and nothing on a 2000 pontiac sunfire thank -you

  15. Matt says:

    For some reason my blinker flashes with the switch in the off position UNTIL I turn my headlights on, that’s the only time it will stop blinking. I do have a blown headlight bulb on the left side, which is also the blinker that is malfunctioning. I’m not sure if the headlight being out is relevant or not seeing as though my blinkers and headlights have separate housings. Anyone offer any advice?

  16. den says:

    There’s a wire going down too your brakes make sure it’s pulled in all the same had the same problem

  17. den says:

    There’s like a relay down there its what makes the clicking noise when you turn on your signal! !!

  18. nandu says:

    Please advise what will be the problem if my Toyota Corolla 2000 car both signal lights are not working. I know that bulbs are fine because it was recently changed.



  19. Stan says:

    I have a 2000 Buick La saber. The left turn signals is acting like it is on double time. The Left rear turn signal lightbulb was out so I replaced it. It still doing The left turn signal double time, with no light on the left rear signal. Next I replace the 15 amp in the fuse box. Still not working right.
    What is your thinking to resolve this problem?

  20. Bob Marshall says:

    Turn signals quit – hazards work. ’99 Olds Aurora.

    Thanks -


  21. vance wright says:

    my left turn will not stop bilking

  22. peter conti says:

    I have a different problem on my 98 max. My passenger side front blinker is not working while the rear one is working (The driver side blinkers are fine). I checked the bulb and even replaced it with new one, it’s still not working. This is actually the second time is happening. The first time, I gave up and suddenly (I think after I hit a bump) it started working again. This time, my wife hit another car (no damage to the cars), and it quits working.

    I’ve got different opinion about the cause of the problem. It’s not the bulb. It’s not the relay because the rear one is working. It’s probably the ground connection.

    Anyone experienced the same problem?

  23. Hector Lopez says:

    My 240, 1993 volvo teun signal does not work some times. I want to know what is wrong.

  24. tom says:

    I have a 2005 Grand Prix that the front passenger side does not work, I have replaced the bulb and tested both the old one and the new one, it still does not work. The signal light flashes fast on the rear indicating the bulb is blown but the bulb is ok?

  25. Jasmine says:

    I have a 2000 infiniti and all of a sudden my turn signals stopped working, then the next day they worked and stopped again. All my other lights work. My question is how would I know if I need to replace the signal switch or just replace the signal relay?

  26. John says:

    I have a 2005 Mits Montero, left signals work fine, right signals not working at all. Hazards on, only left side flashes, not the right. Have checked all fuses, and all bulbs – are fine. Flasher of course is working… so what could the issue be?

  27. Thomas Smith says:

    I have a 2009 jeep liberty and the emr flashers work but the turn signals don’t flash what the matter

  28. mark oppie says:

    1987 Chevy Celebrity: All lights are working and I just replaced the flasher with the proper part.It has an X and L terminal.still no blink!!! I have 12 volts at the beck of the socket at all times i.e. key on or off, signal stalk up down or in between. Please advise as even getting to the flasher was a nightmare.I had to drop the steering column to even locate the flasher

  29. Alex says:

    I have a 2000 Mitsubishi mirage the light bulbs and fuses are good but I still can not find out how my signals don’t work

  30. bill says:

    I have a 1999 Miata flashers work then stop then after a while they work again hazards also

  31. Ashley says:

    I have a 2003 Ford Ranger. My arrow on dash board is no longer lighting up and my front driver side blinker isn’t working. I have checked fuses, light bulbs, and the flasher and it still doesn’t work. Advise?

  32. billy says:

    I replaced my key switch in my ford ranger after I crank it the turn signal wat work I turn the switch as im almost cranking it again then they work what is the problem

  33. Dave Kutscher says:

    95 Ranger, turn signals and hazard not working. replaced switch no help. check fuses ok, checked flasher voltage ok. is this just a failed flasher ?

  34. boris says:

    I have a 1996 Plymouth voyager left side turn signals work, right turn signal front works but the back does not, I changed the flasher relay and checked the bulbs, bulbs are in working condition and I cant find the problem


  35. julie says:

    I have a 94 chevy astro. Rear signal light wasnt working so i replaced the bulb which was burned. Replaced the socket because it looked like it was burned too. After replacing the socket i put in a new bulb but it blew off. what can i do now, please help

  36. Clifton says:

    I have a 2007 Honda Accord and the right turn signal blinks very fast. I was in an accident and my light was smashed so I replaced it myself and its been blinking fast but running and lighting up fine. It just recently stopped running when I have my lights on, it still blinks but it looks like its out when I’m driving. Any help would be appreciated.

  37. James Dakota Bennett says:

    I have an ’06 Pontiac Grand Prix (Base Sedan), all my blinkers are working, tail lights, headlights everything. But the rear passenger side blinker is not blinking. The bulbs on but it won’t blink. Have 1 Hazard/Signal fuse in the inside compartment (20w) and it’s fine. I’m confused here.

  38. Peter Wainwright says:

    I have a 1999 plymouth grand Voyager with intermittent signal problems.

    Right turn signal works all the time
    Emergency Flashers all work and work all the time when flasher button depressed.

    All bulbs are good.

    Left turn signal may work randomly for a few miles and then suddenly stop. Sometimes it will not come back for days and will not stay working for more than a few miles on any day.

    Already replaced turn signal lever switch (multifunction switch) and it did not make an improvement.

    someone told me it could be ignition switch related. Another person says flasher relay unit.

    Any suggestions?

  39. Hector Lopez says:

    I have a 240 volvo from 1993, the left driver’s front turn signal does not work. It will not blink. Pleaselet me konw what is wrong.

    Hector Lopez

  40. Linda says:

    I have a 1998 ford contour and my turn signals or flashers will work.Have replaced the switch and the relay in the switch checked all bulbs and fuses and still nothing….please help me

  41. ben says:

    My turn signal works just makes screeching noises and will get stuck and go slower than usual

  42. Ong says:

    Check your headlamp earthing make sure it is tighten and if possible use sand paper to sand the nut and the car that it is connected

  43. Karly says:

    I have a 99 ford escort se wagon. My right turn signal doesn’t work and neither does my right hazard. I have replaced fuse after fuse, replaced multiple switches as well, also replaced the bulbs. It is neither of these things and I am at my wits end. Help

  44. Bridget says:

    I have a 96 dodge neon. My blinkers stopped working after the car sat for 7 months. It did get a heater core replaced. When I turn on my blinkers the passenger front doesn’t turn on at all. But they blink really fast. I checked all bulbs they are good. I replaced the bulbs of the ones that are not working and they still don’t turn on. Then when I turn on my headlights or flashers on the flashers won’t blink and none of the blinkers work but in the dash the indicator the left side only stays on. What can this be?

  45. Richard says:

    i replaced the multifunction switch on our 98 f150 xl 4.6l 2wd due to loss of turn singals and brake lights. so i replaced the multifunction switch and still dont have either and fuses and bulbs are good along with the plugs under the truck and the bulb sockets. please help me i am lost and out of ideas my email is

  46. Dan says:

    Both turn signals come on in back of my 79 Gmc c15 when i turn on one side the front are ok it’s just the back?

  47. KT says:

    I have a 2001 GMC Yukon. Just installed new covers, sockets and bulbs in front and back. I have emergency blinkers and the right turn signal, front and back. No left signal. Lights will go on, but no blinking. Signal is on on my dash, but doesn’t blink.

    Flasher replacement needed?

  48. Woody says:

    I have a ’93 GMC Sierra and my rear break lights and blinker will work every once in a while (very rarely). The left side lights will work just fine every time, not the same with the right side though. The right side lights very seldom work. The front are okay.

  49. David says:

    I have a 03 gmc sierra. both turn signals do not work. Checked all the fuses and they are all good. Already replaced the flasher relay module and problem persists. hazards work though. replaced turn signal switch with a good used one and signals still do not work. Need help for a new angle for troubleshooting.

  50. kidd says:

    Hi! i have a chevrolet optra 2007 and the hazard lights won’t work unless the turn signal switch is on (either left or right) together with the hazard button. Turn signals work perfectly fine. thank you.

  51. Mir says:

    Hi! So I put my left blinker on to turn into my driveway today, and it didn’t turn off. Even when I manually put the lever in the off position, it stays blinking. But the weird thing is, is that it will turn off when its in the right position. The right blinker also doesn’t work in the right position, so I have no right blinker. To make it simpler, here’s how it is=

    Left position=left blinker
    off position=left blinker
    right position=no blinker

    I drive a Saab 9-3 convertible. Any suggestions?

  52. Aleem says:

    I have a 1995 Mercury grandmarquis. It marks that it is over heating but it really doesn’t. I changed the termalstat and it still marks the over heat can someone please help me. I think it is the coolant sensor because the fan is good and so is the radiator????

  53. Justin says:

    I have a 1996 gmc sierra the turn signals will not work but when I turn my emergency flashers on they only work when I hit the brakes what could be my problem

  54. scott says:

    I have a 2006 ford escape. When I turn on my turn signal, both, left and right come on. It’s like turning on my 4 way flashers. What can I do to fix this? TY

  55. Jenn says:

    I HAVE A 96 Chevy c1500 and my left tail light is not working on the back side ONLY I changed bulbs on the back and also the flashing relay and still not working ONLY the front is flashing…! Any advise thanks

  56. Bob says:

    I have a 1981 ram d250 all the lights were working when it went in for a safety and when I got it home no headlights and signals blink at the same time and when I put the headlights on the blinker indicators both light up really bright can anyone help me

  57. Garee says:

    I have a 2004 Buick Rendezvous.
    Left turn signal works fine.
    Right turn signal works fine in front, but then both left and right rear signals flash at the same time.
    Also, when brake is pressed, only the right rear brake light is lit.
    What is the problem?

  58. SaskBill says:

    Hi – 1991 Ford Ranger Supercab – Rear Stop/Turnlights flash together whenever ignition is on. Hazard lights work normally, brake lights and running lights work OK. When turning left, front signal light and left rear turn light OK; when turning right, fron turn lights and BOTH rear lights flash. Checked front ground on drivers’s side engine compart apron, rebuilt rear wiring harness (PO had cut out the plug and licence light subharness, and left some of the subdived wires dangling, but this did not help. Checked all bulbs and rear sockets.

    Phantom rear flashing goes away when I speed up but dash volatge indicator is always high side of normal. Low volatge problem?

  59. Stef says:

    Hi I have a 95 Ford aspire. Passenger side blinkers work, front driver’s side works but the rear driver side doesn’t. All the other lights in that fixture work, I put another bulb that I know works and it still didn’t work. Any ideas?

  60. don says:

    I have a 2008 frontier 4/4 se 6cyl right turnsignal work fine, left side don’t light up or do notting and the flasher don’t work! can all fuses and bulbs all ok? need help! thanks don

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