LPS circuit

Discussion in 'Electrical Systems' started by ErikNORCAL, Oct 24, 2019.

  1. ErikNORCAL

    ErikNORCAL Veteran Member

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    Used a lighted probe and my “LPS” circuit is dead at the fuse block. Both the 3A little fuse and the spade connector in the next section of the block. The fuse is good.
    Looking for some troubleshooting tips.
    Diagrams indicate this goes to dash lighting “gray” wire and a green wire “temp” (U14 gauges) may be associated. The gray wires I’ve found are dead, no surprise since it’s dead at the block.
    Doing this because I need a lamps source for a new dash cluster.
    Thanks
     
  2. Jim Streib

    Jim Streib https://www.flickr.com/photos/121766713@N04/albums

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    The LPS fuse and neighboring male terminal will only show voltage when the headlight switch is pulled out halfway or all the way AND this voltage can vary depending on the rotation of the headlight knob. One way with the headlight switch halfway out or all the way out might be let's say 12V and then when you rotate the knob the voltage will decrease. This decreased voltage dims the instrument panel lights and whatever filament light(s) may be plugged into the 1/4" male tap.

    Here is an album when I added a light for my heater controls and used the tap in the fuse block so that light as well as the others in the instrument panel dimmed and work together:

    https://www.flickr.com/photos/121766713@N04/albums/72157683583243170

    https://www.flickr.com/photos/121766713@N04/35464756712/in/album-72157683583243170/

    Jim
     
  3. ErikNORCAL

    ErikNORCAL Veteran Member

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    Wow, thank you Jim! Would’ve never figured that out.. glad I asked.. and thank you for the picture instructions - definitely can understand that!
     
  4. ErikNORCAL

    ErikNORCAL Veteran Member

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    Well - no bueno. It looks like someone did a similar mod, tapped the male terminal and ran a string of bulbs and sockets to fit the dash and other areas off this circuit.
    How is power connected to this circuit in the block? Also looking on the firewall side - anything in particular I should see?
     
  5. Jim Streib

    Jim Streib https://www.flickr.com/photos/121766713@N04/albums

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    So the fuse has no power with the headlight pulled out and then rotated fully one or the other direction ?. Do these bulbs tapped into the male terminal light up ?

    If everything on the LPS fuse and the male tap are dead or show no power even after pulling out the headlight switch halfway or fully and then rotating the headlight switch fully one way and then the other then it's possible that the headlight switch has an issue and/or the wiring to and from it. Maybe to rotate the switch a bunch of times fully one way then the other as sometimes the contacts get corroded and foing this sometimes can clean the connections.

    Off of the headlight switch there is a smaller gauge green wire which then goes down to the one fuse clip in the fuse block. The other clip closest to the male terminal on the backside will have a small gauge gray wire attached to it. This gray wire goes into the loom and then splits to different things like to an illumination bulb for the heater controls, an illumination bulb for the radio, and then to the illumination bulbs in the instrument panel. You may have to get at the connector for the headlight switch to verify power on the small orange wire and the small gauge green.

    I'm thinking that there is a fuse protected wire out of the fuse block that goes to the headlight switch and it is NOT the 14 gauge Red wire which normally is power for the headlights and I think this supply wire is also tied to another fuse in the fuse block, possibly the fuse for the parking lights ?. It seems to me if the parking lights do not work or that fuse is blown, then the LPS circuit is also dead.

    I would check the rest of the fuse in the fuse block and verify you have constant power on the proper fuses and also check on the clip sides as I have seen people touching the barrel of the fuse and not always showing power due to corrosion between the barrel fuse end and the clip.

    Jim
     
  6. ErikNORCAL

    ErikNORCAL Veteran Member

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    Thanks again Jim. Will run down this list in the next few days. All the Exterior lights (headlights, park, turn, etc) work which led me to think this would be easy going in.. ha! The lamps part is cobbled together, the connector is soldered to the male terminal. Took me a while to figure out why the wire wasn’t coming off.
     

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