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Weird electrical problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by NCJoeG2, Mar 19, 2017.

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  1. NCJoeG2

    NCJoeG2 New Member

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    Hey folks! First post here! What a wealth of information on this forum.

    So, I own a 2007 Prius with about 135k miles. My wife was driving it the other day, and she noticed she only had one headlight. I recently replaced these, so the bulbs are probably fine. A little later, she noticed a strange clicking sound coming from the engine compartment. She parked it and I came and got it later. On my trip home, there was no clicking, but lots of other problems. The low beams would not work at all, but both high beams worked. The heat/AC fan went out for a few minutes, then came back on after turning it off for a little while. All three passenger window switches on the drivers side panel do not work, but the switch for the driver's window works fine.

    I tested the batter today using the proprietary Prius diagnostic mode. Readings were 12.1 v with one push, 11.8 v in ACC mode, and 14.2 v in ready mode.

    I cleaned the 12 v battery terminals, even though there was no sign of corrosion and the battery readings seemed fine. This did not fix the low beam issue or window issue, and the readings remained the same after cleaning. I also made sure the ground connection to the body was nice and snug.

    Any clue what could be the cause of this? Just for information's sake, the car was recently run for a short period of time with no upper splash guard installed in the engine compartment. During this time it was driven a couple times in rain. Could this have fried something?

    Any help is much appreciated.
     
    #1 NCJoeG2, Mar 19, 2017
  2. xliderider

    xliderider Senior Member

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    The voltages are low, you need to recharge the battery, or if it's more than 4 or 5 years old, replace it.
     
    #2 xliderider, Mar 19, 2017
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Your title implies that you think one root issue is causing these various symptoms. I think it is more likely that the car has multiple issues.

    1. Who normally drives this car? Did all these problems happen at once, or is this your wife's car, and she did not notice (or report) the problems slowly developing over time?
    2. I assume your Prius has halogen headlights (not HID).
    3. Since you say you recently replaced the headlight bulbs and both low beams do not work, check the DIM relay. This is located in the main relay/fuse box next to the inverter, in the engine compartment.
    4. It could be that your cabin blower motor is getting intermittent and needs to be replaced.
    5. You'll need to open up the door panel for access to the power window switches. Perhaps you have corrosion developing in the wiring harness, or maybe you need to replace the switch assembly.
    6. The 12V battery is low, but that is not the cause of the various issues noticed.
     
    #3 Patrick Wong, Mar 19, 2017
  4. NCJoeG2

    NCJoeG2 New Member

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    Ok I'm a bit of a doofus. I did some more poking around, and as it turns out, the window lock was on. When I was driving the car home the other night I guess I just didn't notice or think to check.

    So, still that leaves the low beams and the blower motor. I visually checked all the fuses in the fuse box under the hood, and they all look fine. I also could hear both the high beam and low beam relays click from manipulating the headlight switch. Honestly this is the only way I know to check relays.

    Patrick, to answer your first question, my wife has been driving it full time the past few months. She's normally really good about letting me know any time anything with the operation of one of our cars changes.
     
    #4 NCJoeG2, Mar 19, 2017
  5. Samprocat

    Samprocat Active Member

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    Without proper electric diagnosis there is not much anyone will help you here....you need to have car inspect by someone who can trace electrical diagrams and pinpoint the cause of your problem....


    Posted via the PriusChat mobile app.
     
    #5 Samprocat, Mar 19, 2017
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you can hear the relay click, then you should be able to find it.

    If you can find the relay and want to test it, you will need a 12V power supply (for example, two lantern batteries in series) and a digital multimeter. The relay is SPDT (single pole double throw) which means that it is a two position switch.

    Pull the relay out of its socket. A small flat-blade screwdriver may be necessary to help pry it out.

    The relay had five terminals, two are for the relay coil. Those two terminals are numbered 1 and 2, and will measure ~100 ohms resistance. That leaves the other three terminals for the two position switch. One terminal, #3, connects to the pivot of the switch while the other two terminals, 4 and 5, connect to the switch contacts.

    When the relay has no power applied to the coil, you should measure 0 ohms resistance across terminals 3 and 4. When 12VDC is applied to the relay coil, you should measure 0 ohms across terminals 3 and 5. If your findings are different then you know the relay is bad and should be replaced.

    Or, instead of testing, you could visit your local Toyota dealer parts department and drop $75 on a new relay, and see what happens.
     
    #6 Patrick Wong, Mar 19, 2017
    Last edited: Mar 19, 2017
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  7. NCJoeG2

    NCJoeG2 New Member

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    Thanks everybody for your help. I've driven it the past couple days, and the blower motor has been fine. I'm thinking that was just a fluke. Maybe that's the weird sound my wife was hearing.

    About the low beam relay, is the same relay used anywhere else in the vehicle? If that's the case, I could just swap them to test it.
     
    #7 NCJoeG2, Mar 21, 2017
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I will leave it to you to find that relay, and compare its appearance and part number to other relays installed in the various relay boxes.
     
    #8 Patrick Wong, Mar 21, 2017
  9. edthefox5

    edthefox5 Senior Member

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    If you are using auto parts store headlight bulbs although brighter than the stock bulbs they won't last long. Given how hard they are to replace go with one that lasts.
    Use the oem bulbs. They last years. Also like me you may have burned up light sockets . I has to replace mine in addition to new bulbs. You can tell as they have burn marks on the white plug.
    If your headlights went out it's Time to rebulb the whole car. Replace
    All 3 bulbs in the headlight and the 2 rear bulbs each. Rears are easy,

    And get ready to replace the blower motor, that's how it fails,......just stops working....starts again......next it just stops. For good. Like my 07.

    Go online for original Toyota parts. For the blower sometimes on eBay you
    Will see a new one cheaper. Don't put in a used fan. It's a hassle to install
    You won't want to go back in there.
     
    #9 edthefox5, Mar 22, 2017
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