Results 1 to 7 of 7

Thread: Voltage drop at idle...

  1. #1
    Registered Otto Man's Avatar
    Join Date
    Jan 2002
    Location
    South Milwaukee, WI, USA
    Posts
    403

    Voltage drop at idle...

    I replaced my alternator (180 amp!!) and battery last week, at start up (fast idle) and while driving (or parked and stepping on the gas) the volt meter on the gauge cluster is up above 13 and the reading at the battery is about 14 volts.

    After it is warmed up, the reading drops to 12 at the battery and drops below 13 on the gayge cluster. This wouldn't be a concern, but the headlights and other accessories dim/slowdown noticeably when sitting at stop signs, etc.

    I don't remember this happening before the old alternator went bad. It seems like the battery should read around 12 when the car is off and 13-14 at idle. Could it be a bad ground? Broken wire? Is this normal?

    Thanks for the help.

    ------------------
    87 XJ Pioneer
    2003 TJ Sport, 42RLE Auto, 4.0L, Heated Seats, 3.5" Rancho Short Arm, RS9000XL Shocks, 33x12.5R15 DuraTrac on Black Painted Canyons, 1.5" Wheel Spacers, Smittybuilt Classic Rear Bumper and Tire Carrier, Speedo Corrected, Rustys Tranny/Engine Skid, Cherry Bomb Cat Back Exhaust
    http://www.jpmagazine.com/jeepshots/...ots/index.html

  2. #2
    there can be only one
    Join Date
    Sep 2000
    Location
    High Ground, NC
    Posts
    1,103

    Post

    i seem to recall hearing something about high-amp (maybe 140+ amps? don't know the rule of thumb) alternators being funny at idle-maybe part of the reason police xj's often have an idle switch. this all from messages i've read on this forum, so if you do a back-search on higher-amp alternators, you might see what i'm talking about.
    push the seat back a little lower-watch light bend in the blower. planets align. a king is born.

  3. #3
    Registered
    Join Date
    Jan 2002
    Location
    Bergen County , NJ
    Posts
    305

    Post

    At idle mine dim too. Stock alternator. They really dim when I am running the window defroster,fan defroster and roll up my windows. Cant wait till I hook an amp up and drain it even more.
    2001 XJ - Jeep Cherokee 4x4 - 60th Anniversary Edition - Black - 4.0L Power Tech I-6
    4 Speed Automatic Transmission - AW4 Command Trac (NP231) - Axle Ratio (3.55)
    16 Inch Aluminum 5 Star Rims - Tires - P225 / 70R16 - Goodyear HP
    AM/FM/CD/Cassette/EQ - Limo Tint - Husky Liners - Police Scanner - Radar Detector
    Stock and Staying That Way
    ----------Future Mods----------
    Drawtite Trailer Hitch - Class III
    Hella Foglights w/ Factory Switch
    Window Ventvisors
    New Speakers and Amplifier

  4. #4
    If your alternator is putting out around 13v, it should be working fine. Lights dimming, especially with a 180 amp unit would indicate too much power draw or unclean connections. One real handy tool to have is an amprobe/voltmeter. This will enable you to take amp readings under full load and voltage readings, not at the same time, though. If your full load amp reading is under 180, then i would look at all connections, at the battery and the other terminations. Good luck, Jim

  5. #5

    Post

    One other thing, If you want your in dash voltmeter to read more accurately, run a larger guage wire from the battery to the meter. Later, Jim

  6. #6
    Registered
    Join Date
    Jan 2002
    Location
    Erie, PA
    Posts
    956

    Post

    You might also check the belt. Loose belt or slippage will cause this. Fact of life for me on a rainy day. I'll get that sucker changed someday.

    ...Wishin' the temp would rise above 40*.

    ------------------
    Jack
    '99 XJ Sport - Stock
    K&N, Mopar Hooks, Skids, BFG ATKO 235's
    Hidden Hitch
    '99 XJ Sport - Chili Pepper Red - 4.0, AW4, NP231
    5" Lift, 33" M/T, Front 44 Electrac, Rear 44 Detroit
    Click Here for Specs

  7. #7
    Registered Otto Man's Avatar
    Join Date
    Jan 2002
    Location
    South Milwaukee, WI, USA
    Posts
    403
    Can I attach the battery charging cable from the alternator directly to the battery instead of going to the starter solenoid? I will try some of your other suggestions when I have a moment.

    ------------------
    87 XJ Pioneer
    2003 TJ Sport, 42RLE Auto, 4.0L, Heated Seats, 3.5" Rancho Short Arm, RS9000XL Shocks, 33x12.5R15 DuraTrac on Black Painted Canyons, 1.5" Wheel Spacers, Smittybuilt Classic Rear Bumper and Tire Carrier, Speedo Corrected, Rustys Tranny/Engine Skid, Cherry Bomb Cat Back Exhaust
    http://www.jpmagazine.com/jeepshots/...ots/index.html

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