1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Did I fry my dimmer?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by finiyon, Apr 16, 2005.

  1. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    I just installed an OEM EV switch and it works.

    Now the problem: the dimmer wheel is no longer dimming the dash display as it used to. In mid range, it puts just enough power to barely show the display and the MFD flickers between regular and bright display. When the switch is clicked to "on" all works fine. When the switch is all the way down all works fine.

    How much does a dimmer cost?

    2005 Prius
     
  2. Frank Hudon

    Frank Hudon Senior Member

    Joined:
    Jan 11, 2004
    4,147
    18
    0
    did you just dislodge the connector on the wire harness and it's making intermittent contact. That would be the first thing I checked.
     
  3. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    That was my first check. All of the pins are well set. Could it be something worse? the buttons on the sides of the MFD barely light at all.
     
  4. naterprius

    naterprius Senior Member

    Joined:
    Mar 15, 2004
    1,843
    11
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    My guess is you caused a poor connection in the main dimmer switch wiring. Either that or you miswired the EV button so that all dimming must go THROUGH the EV switch before going to the rest of the car.

    I really doubt it's the dimmer; I think it's a mechanical rheostat; those are pretty hard to destroy. I can't think of anyway to feed 12 volts through it that would cause damage.

    Nate
     
  5. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    I disconnected the EV switch and the problem remails. Could a pin on the harness (dimmers) go bad after just one removal? The dimmer does still vary its resistance when the wheel is rolled.

    Back when I was towing a trailer it was always the ground. What are the odds on one of the Radio Shack connectors cutting a few too many strands on the dimmer wires?
     
  6. naterprius

    naterprius Senior Member

    Joined:
    Mar 15, 2004
    1,843
    11
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    I still think you have bad wiring. Make sure that most of the copper strands still go through to complete the circuit at the rheostat.

    Nate
     
  7. Frank Hudon

    Frank Hudon Senior Member

    Joined:
    Jan 11, 2004
    4,147
    18
    0
    if you used "Scotch Lock" type of wire connectors it's very possible you have cut all the wires off on the power wire from the dimmer control. If such is the case, connector type, just pull gently on the wire on either side of the spot where you had the connector and if it's severed the wire will pull apart. I always strip and solder wire joints, then use brush-on electrical tape and then put tape (real) over the brush-on.
     
    ydpplqbd likes this.
  8. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    I cut out the wire taps. Soldered the connections. Used heat shrink tubing. Re-connected the dimmer harness. And . . . still the same issue. I tried with and without the EV switch connected. I also tested the R.S. connectors that I cut out and they tested fine. I tested the dimmer again and can not get an ohm reading other than 0 or infinite. Have I done the difficult to do? ie: killed a mechanical rheostat?

    Forgot to add: the EV light on the switch is not working. I most likely fed too many volt through it.
     
  9. naterprius

    naterprius Senior Member

    Joined:
    Mar 15, 2004
    1,843
    11
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    This is really wierd. Did you by chance pull the pins out of the connector and put them back in the wrong slots?

    Nate
     
  10. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    Nope. What should I be getting for the resistance value across the dimmer? Is there anything that I could clip in to try and eliminate the dimmer switch as the issue?
     
  11. naterprius

    naterprius Senior Member

    Joined:
    Mar 15, 2004
    1,843
    11
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    Check resistance from the battery negative terminal to pin 5 (white with black stripe). It should be zero Ohms. (If your leads are too short check pin 5 against ground).

    Check the Voltage at the positive terminal of the battery compared to pin 2 (gray wire). The difference is the voltage drop and should be essentially no difference.

    I'm not sure what should happen at pins 6 and 7 but I think at full brightness you will either get full continuity to ground or full voltage. (I don't know which).

    Whatever these are, they should vary as the rheostat varies position. (Resistance should increase or voltage level should fall).

    If you want, take some resistance readings through the rheostat at different positions. I'll compare against mine tomorrow (monday) night.

    Nate
     
  12. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    Okay, here we go.
    w/o the dimmer switch installed:
    pin 5 -- to ground (collection of grounds just behind the switches) = 0 ohms
    pin 2 (gray) -- to ground (pin 5) = 8.56/8.16 vdc (power off/power on)
    pin 6 (red) -- to ground (pin 5) = 8.62/8.16 vdc
    pin 7(blue) -- to ground (pin 5) = 0.02/0.04 vdc

    w/ the dimmer switch installed:
    pin 2 -- pin 5 = 4.76/5.25/7.86 (down/mid/clicked to top)
    pin 6 -- pin 5 = 4.78/5.86/8.14
    pin 7 -- pin 5 = 0.02/4.03/8.14

    Thank you to all for the time and efforts !!!
     
    ydpplqbd likes this.
  13. DanMan32

    DanMan32 Senior Member

    Joined:
    Aug 27, 2004
    3,799
    26
    0
    Location:
    Tampa Bay, FL
    Pin 2 should be 12V from the 7.5A panel fuse. Pin 2 is a gray wire right? It goes to pin 6 of connector 5M (instrument panel connector).

    Check that fuse, I suspect you blew it.

    You are checking pin 2 with the tail light on, right? As the panel fuse gets its power from the tail relay points.

    You might want to be in READY to be sure you have 14V from the DC/DC converter, and not a weak battery reading only 8 volts!
     
  14. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    Go Dan, go Dan, it's your birthday, it's your birthday!

    The word "fuse" spoke to me.
    Do you know what it said? Dohh !!! :oops:
    It all works. The switches and the lights.

    Thank you Frank.
    Thank you Nate.
    Thank you Dan.


    I just made my donation.

    P.S.: What do you think of my avatar?
     
  15. naterprius

    naterprius Senior Member

    Joined:
    Mar 15, 2004
    1,843
    11
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    Glad to hear you fixed this. Do you know why you blew the fuse? (Did you touch two wires together before insulating?)

    If you don't know why it blew, keep an eye on it to make sure it doesn't happen again. If it does, double check your wiring.

    Nate
     
  16. DanMan32

    DanMan32 Senior Member

    Joined:
    Aug 27, 2004
    3,799
    26
    0
    Location:
    Tampa Bay, FL
    It's my birthday? Gee, I thought it was in January! Do I get a birthday present? :wink:

    Seriously,
    Me too, glad to hear it. I was trying to figure out that if that fuse was blown as I had suspected, where were you were getting 8V from? I believe it was coming from the combination meter that was expecting a source, but ends up providing a weak source.
     
  17. finiyon

    finiyon Re-Member

    Joined:
    Mar 25, 2005
    66
    1
    0
    Location:
    Philly, PA
    Vehicle:
    2008 Prius
    I must have crossed two wires early on in the process.

    As for the 8 volts . . . the displays must be getting power from two sources and I was picking up a few volts passing through to ground.

    The EV switch is doing it's job. I got 56.9 mpg on my 50 mile round trip to work today. I "only" got 50 mpg last week.
     
  18. Beacher

    Beacher Member

    Joined:
    Apr 14, 2005
    103
    0
    0
    Location:
    Oregon, Wi
    You electro geeks are something else! Nice to see such a nice sense of community.
     
  19. DanMan32

    DanMan32 Senior Member

    Joined:
    Aug 27, 2004
    3,799
    26
    0
    Location:
    Tampa Bay, FL
    <div class='quotetop'>QUOTE(finiyon\";p=\"82934)</div>
    Well, what I originally found perplexing was everything connected to the pin 2 wire were getting THEIR 12V feeds from the same fuse... except the combination meter.