Results 1 to 8 of 8

Thread: How do I check my headlight bulb w/ multimeter?

  1. #1
    Kid Forever trayson's Avatar
    Join Date
    May 2003
    Location
    Vancouver, WA
    Posts
    856

    Default How do I check my headlight bulb w/ multimeter?

    Okay, how can I tell for sure with my muti-meter if my headlight bulb is out?

    I have PIAA bulbs in my headlights. One of my headlights is out right now. I figure it's just the bulb. After looking on the internet, I found that the superbright bulbs that are in my Jeep are REALLY expensive. $50 - $60 for one bulb is what I'm finding!?!?!

    So, I want to really make sure that the bulb is out.

    I took the bulb and tested it on the Ohm setting with my multimeter. I took 2 bulbs that were good and tested them. When I touched the leads to the outside & center of a good bulb, my multimeter said "short". When the terminals weren't touching the bulb, it said "open".

    Here is what my H4 bulb looks like:

    For illustration let's number the terminals from top to bottom 1, 2, 3. The parallel terminals are 1 & 3. The center one that's facing 90 degrees different from the other two is #2.

    When I hooked up the multi-meter to two of the three leads, it gave me the following results:
    Hooked up to 1 & 3, the two parallel terminals: Short
    Hooked up to 1 & 2, two perpendicular terminals: Open
    Hooked up to 2 & 3, the other two perpendicular terminals: Open

    So, basically energy isn't flowing through either of the perpendicular terminals, but will flow through 1 & 3, the parallel terminals. Does this confirm that my headlight bulb is really burnt out or does it tell me something else?

    Help me out!!

  2. #2
    Registered roadkill's Avatar
    Join Date
    Nov 2001
    Location
    TX
    Posts
    2,006

    Default

    why not just do an old school test and swap the bulbs? good to bad and see what happens.

  3. #3
    Registered
    Join Date
    Nov 2001
    Location
    Austell, GA
    Posts
    97

    Default

    Or use your mulitmeter on the socket in the Jeep to see if it's getting 12V.
    '98 TJ

  4. #4
    Brighter than the sun... Oman Jeep's Avatar
    Join Date
    Aug 2001
    Location
    Dubai / Oman / Saudi Arabia
    Posts
    10,446

    Default

    Swap left and right bulbs and see what happens.


    Make a note of which side wasn't working before

    2001 TJ Sport | D44 LS | Dick Cepek 4" | 33x12.5 | HID Headlights
    Road Armor 501G2 Matrix Bumper | MileMarker 9000lb | PIAA 1400x
    PIAA 1100x | PIAA 510 | Bestop Safari top / Windjammer / Duster
    Raingler Grips | HP Ipaq Mount | KC 100W Daylighters | CarDomain
    AEV Heat Hood | Kilby Hood Lift | Dome Light Kill Switch | Hood Lock
    AutoDimming Rear View Mirror | JBL 5.25" & 6.5" GTOs | Center Console

  5. #5
    Drillers do it deeper BlueJay's Avatar
    Join Date
    Apr 2000
    Location
    Seria, Brunei darussalam
    Posts
    1,180

    Default

    According to the wiring diagram, one connector is ground, one is for main beam, and one for dipped beam.

    You should read zero resistance between ground and either beam and infinitive resistance between the tow beams.

    The colouring of the wires is:

    ground = black
    low beam = violet.white
    high bean = red orange

    So look at the connector and see how they are wired to the tabs.

    You can also check the voltage between the ground and wires on the connector whether is show 12v when each light is switched on. If that works then the lamp would be faulty

    PS wiring is based on 1998 TJ
    98 TJ, 4.0ltr, Hard top

    Adapt, Improvise, Overcome

  6. #6
    Registered
    Join Date
    Mar 2002
    Location
    Greenwood Lake, NY
    Posts
    282

    Default

    Quote Originally Posted by trayson

    I took the bulb and tested it on the Ohm setting with my multimeter.

    When I hooked up the multi-meter to two of the three leads, it gave me the following results:
    Hooked up to 1 & 3, the two parallel terminals: Short
    Hooked up to 1 & 2, two perpendicular terminals: Open
    Hooked up to 2 & 3, the other two perpendicular terminals: Open

    So, basically energy isn't flowing through either of the perpendicular terminals, but will flow through 1 & 3, the parallel terminals. Does this confirm that my headlight bulb is really burnt out or does it tell me something else?

    Help me out!!
    From what you are saying it sounds like you have a burnt high or low beam. When it reads open there is no connection between the two terminals. Basically the filament inside the bulb is broke. You meter reading short is most likely just it getting a high resistance through the filament which would be normal.

    Before you pulled the bulb out did the high beam work?
    Also as stated above. Swap it with the good one and you will know right away.
    '97 Sahara - Eaton Supercharged Six, Centerforce Dual Friction, NV4500, Atlas II, 285/75r16 Baja Claws, 3" Tera lift, Tera Long Arms, Currie Adjustable Front Track Bar, Tera QD's, DT3000's, York OBA with 2.5 gallon airtank, Mike Leach Header, Herculined inside and under, Cobra C75WXST, Currie Fabricated 9 housing with high pinion third member, Detriot Locker 4.56 gears, Wilwood rear disc, Warn 9.5ti, MORE MML & JKS 1.25 BL, Alumiflex tirerod sitting in a box.

    My Jeep Site

  7. #7

  8. #8
    unRegistered
    Join Date
    Jul 2000
    Location
    El Dorado County, California
    Posts
    4,465

    Default

    Quote Originally Posted by trayson
    Thanks guys ALL great ideas. Sometimes you can't see the forest through the trees!!!
    especially if its at night, and your lights aren't working

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Jeep Parts | Jeep Accessories | Trektop NX | Jeep Seat Covers | Jeep Wrangler | Jeep Wrangler Parts | Jeep Wrangler Accessories | Bestop | Jeep Tires | Jeep Stuff | Jeep Wrangler Tires | Jeep Wheels