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Dimmer switch differences

Discussion in 'Gen 2 Prius Accessories & Modifications' started by peecee, Jun 7, 2017.

  1. peecee

    peecee Member

    Joined:
    Apr 14, 2017
    67
    39
    1
    Location:
    Annapolis, MD
    Vehicle:
    2004 Prius
    Model:
    II
    While preparing to swap out the lower steering column surround on my 04, I noticed there are a few differences between it and the one from an 08 I picked up at the junkyard.

    1. The switch in the 04 is physically bigger than the 08
    2. The wire interface is different, so I can't use the one from the 08
    3. There are three holes in the 08, but only two in the 04
    4. The openings are "keyed," so only a specific switch will fit in each opening.

    I searched and didn't see anyone mention these differences. Before I wire an adapter from the 04 wiring to the 08 switch, does anyone know if the new dimmer switch is compatible with the older wiring of the gen 2? It seems strange that the gen 2 uses two different kinds of switch size formats. I've only ever seen one EV switch for the gen 2 models, and apparently it fits in either hole. Since they're different sizes, that doesn't make sense.
     
    #1 peecee, Jun 7, 2017
  2. peecee

    peecee Member

    Joined:
    Apr 14, 2017
    67
    39
    1
    Location:
    Annapolis, MD
    Vehicle:
    2004 Prius
    Model:
    II

    I've finally found a dimmer from a newer gen 2 to match the hole in the under dash trim that I swapped out. It's been bugging me that the older switch is just hanging out of the hole.

    The question is, what's the extra wire for from the new dimmer? Left is my 2004 dimmer, right is from a 2009 dimmer. Before I cut wires to splice in the new plug, I'd like to know if I'm going to have any problems.
     
    #2 peecee, Jul 3, 2018
  3. ITBland

    ITBland Active Member

    Joined:
    Jun 22, 2017
    433
    273
    3
    Location:
    New Orleans, La area, US
    Vehicle:
    2011 Prius
    Model:
    Three
    2006-2009 added an extra wire so that the Rheostat (dimmer control) is powered when the ignition is on, not just when the lights are on. Even though the name is "rheostat" (literally: variable resistor) it contains more than just the wheel, it contains a circuit I presume is similar to a home light dimmer. It controls the current available to various lights and LEDs in the dash and is read by the Combo Meter and then sent on to the MFD and radio. Since the Combo meter can be swapped into a 2004-2005 Prius (Combination Meters that stop at 299,999 miles, Who's affected and what you can do about it.) the signals must be the same, you would just need to find ECU-IG 12v+ somewhere to tap into. (Should be Fuse #7, 7.5A in the Instrument Panel fuses)
    2004-2005: Prius_2004_Rheostat.JPG 2006-2009: Prius_2006_Rheostat.JPG
    The wire colors are the same for the 4 wires common to both, the extra black (or is it Blue?) wire is the 12v+ IG wire.
     
    #3 ITBland, Jul 3, 2018
    Last edited: Jul 3, 2018
    ydpplqbd likes this.
  4. peecee

    peecee Member

    Joined:
    Apr 14, 2017
    67
    39
    1
    Location:
    Annapolis, MD
    Vehicle:
    2004 Prius
    Model:
    II
    Thank you @ITBland! That is great info! Since I’ve already swapped my CM for a newer one (thanks @Texas Hybrid Batteries!), this makes perfect sense.
     
    #4 peecee, Jul 3, 2018
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