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Auxiliary battery drain (overnight!) on dome circuit

Discussion in 'Gen 2 Prius Technical Discussion' started by djimbuser, Dec 8, 2019.

  1. djimbuser

    djimbuser Junior Member

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    I bought my 2007 used with this pre-existing issue. The dome fuse was missing when I bought it.

    Without dome fuse: No power locks, rear hatchback is locked, dead garage door transmitter buttons, VSC error light, rear wiper motor on always, car remembers climate settings.

    With dome fuse installed most everything works perfectly except the system-off power draw.

    It’s not a dome light left on or bad aux battery. I have tested current draw on the dome circuit and it’s quite high with the system off.

    My mode of use for the car has been to religiously remove the dome fuse when parked and reinstall it before powering the car on. In doing this it always forgets the climate settings. Amazingly if I don’t reinstall the fuse before turning the car on again it remembers the climate settings.

    Any suggestions welcome. I’m getting close to wiring a dash toggle switch for this circuit!
     
  2. bisco

    bisco cookie crumbler

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    you might have to. electrical problems can be a nightmare for those of us without troubleshooting and schematic expertise.

    if the climate is acting backwards, maybe the head unit is the problem.
     
  3. valde3

    valde3 Senior Member

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    As the problem is constant it is simple (relative to other electrical faults) to determine. Just check where the current is going with a meter (better with current clamp meter) and wiring manual. With that you will find the part or wire that's faulty.
     
  4. edthefox5

    edthefox5 Senior Member

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    Is your car a touring model with JBL sound system?
     
  5. R-P

    R-P Active Member

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    What is "quite high"?

    I got a defective clamp meter from someone (just a loose wire) as he got a new one from the Chinese seller. It can measure DC current (which many won't be able to do!!!). As Valde3 said, this would really help finding the issue if the current is above 1A or so, as you don't have to break a circuit and put the currentmeter inline but you can just wrap the 'jaw' of the meter round a wire you want to check and it will measure the current.

    Do check and doublecheck if a (borrowed or planning-to-buy) clamp meter can measure DC-current.

    [​IMG]
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    What you can do is disconnect the negative 12 volt battery cable from the body, isolate and clamp it to a wire, run that out across the hatch threshold and down to the ground. Connect a second wire to ground (maybe just clamp it with the negative cable body bolt), and run that wire out similarly. Close the hatch (the wires will just compress into the rubber weatherstripping.

    Wait about 20 minutes, and leave your fob well away from the car. Then connect up a multimeter to those two wires, set it to amperage scale first, then milliamperes, and see what reading you get.

    Doing this with a third gen, I was seeing around 16~18 milliamperes, with spikes every 5~6 seconds to around 40. The spikes did not seem to sync with the blinking security icon in the dash, but maybe it was; it would seem a likely suspect.

    For the life of me I can't remember how I popped the hatch (it requires power). I would suggest: switch the multimeter back to amperes, then pop the hatch, then disconnect the meter, remove all wires, and reconnect neg battery cable to body.
     
    #6 Mendel Leisk, Dec 16, 2019
    Last edited: Dec 16, 2019
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    I'm going to toss my 2 cents into this. Let's see if I get lucky.....

    The DOME fuse supplies power to the Body ECU.
    1. The Body ECU is connected to all the door courtesy light switches. You may want to ensure one of your door bottom lights isn't staying on, even with the door shut. Don't forget to make sure the little light in the hatch area is turned off.
    2. What many people don't realize is the Brake Control Power Supply also connects to the Body ECU. Where you ask? At the same pin as the driver side door courtesy light switch. The BCPS is the black box mounted just to the driver side of the 12v battery. It's full of capacitors that supply back-up energy for the brake system. These capacitors have been known to go bad and start draining the 12v battery.
    3. Check it out and let us know...
     
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  8. edthefox5

    edthefox5 Senior Member

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    Good one TMR I always forget about that little back up power box back there. Its invisible until it kills you.

    I remember a few posts about that BU box circuit going bad one post it was shorted. Take that plug off measure the dc on it if no dc measure the ohm across it.
     
  9. R-P

    R-P Active Member

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    You mean the plug or the box? Not sure if it is just a box of capacitors, but if there is a short, I assume you will indeed just measure e.g. 10 ohms (about equivalent of a 1A currentdraw draining the battery in a day or two).

    Many multimeters will have a fused current-measuring circuit. I know, as my fuse costs 20$... So what I always do is use bananaplugs with crocodile-clips instead of measuringleads. This makes it easy to short the red and the black bananaplug leads ON the multimeter with a very short green bananaplug-lead. This way all peaks, like the central-locking current will not go through the meter and the (expensive) fuse, but will mainly go through the green banana-plug-lead. Once all excessive peaks are gone, I remove the green lead and all current goes through the meter and is then correctly displayed.

    [​IMG]
     
  10. djimbuser

    djimbuser Junior Member

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    I received my clamp meter today. Before using it I measured current draw on the dome circuit with the car off. I know that the initial draw can be high so I kept watching it for at least a minute and it hovered around 0.57 AMPS. Another thing I noticed is when the circuit is active there's a faint sound coming from the passenger side of the engine bay. Here's a youtube video of the sound - might have to turn up your volume to hear it:



    Listening closely it sounded like it was coming from the window washer pumps. I disconnected the right one and the sound continued but then after disconnecting the left one it stopped!!

    I measured the current draw and it fell to just 19.9mA.

    This wouldn't be the pump motor's fault would it? It's not actually pumping any liquid because the tank is still full. Absolutely no problem leaving this disconnected because it's just the pump for the rear hatchback window.
     

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    #10 djimbuser, Dec 21, 2019
    Last edited: Dec 21, 2019
    edthefox5, R-P and Mendel Leisk like this.
  11. edthefox5

    edthefox5 Senior Member

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    Very good troubleshooting there. I have replaced both washer pumps on my 07 so familiar with this circuit.

    Fuse 20 WSH supply’s 12 volts to one side of the motor plug the other pin on the plug goes to
    What’s called the combination switch which is the right side stalk on the steering wheel. The one that turns on the wipers and washers.
    That combo switch provides ground to that pin to turn on the motor.

    So the motor is not bad it’s just getting a ground somewhere to turn it on. I woukd check that plug to confirm. One side has 12 volts then measure the other pin with an ohmeter to ground to see if it’s shorted to ground.

    It may not be dead shorted but just low enough impedance to turn on the motor.

    The repair is pretty straight forward it’s either that combo switch needs to be replaced or the car is a salvage car and the wire is damaged. Maybe rodent damage?

    Or the clock spring in the steering wheel is damaged? Do all the functions including lights work on the steering wheel?

    Bottom line to much work to repair unless it is the combo switch and other things in that switch start failing.

    Good luck.
     
  12. djimbuser

    djimbuser Junior Member

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    Clock spring seems fine. All functions work in random degrees of the steering wheel.

    I measured the "ground" side of both front & rear washer connectors and they measure "0.36" on the 2K setting of the ohm meter.

    I measured the hot side of both front & rear washer connectors and the front reads "0" and the rear reads "12".

    From what Ed said, the ground side is supposed to be floating?

    Since disconnecting the rear washer plug the car is functioning noticeably better:
    1) It's remembering the climate settings
    2) The FOB lock/unlock functions are far more responsive.
    3) It used to make random bleeps & beeps for 3 minutes after turning off the car and now it doesn't.

    Quite pleased so far!
     
  13. djimbuser

    djimbuser Junior Member

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    With the car off, "IG1 Relay" should not be supplying power to "RR WIP", "WSH", or "WIP" so I don't see why I'm getting 12V at pin1 of the rear washer motor. I'll check for power at those fuses & also see if I can locate junction connector "J8".

    PriusWash.jpg
     
  14. djimbuser

    djimbuser Junior Member

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    Powered ON:

    Front washer connector (Black/Lt blue thick) - Both battery voltage
    Rear washer connector (Violet/Lt blue thin) - Both battery voltage

    Powered OFF:

    Front washer connector - Both 0V
    Rear washer connector - Violet 0V, Lt blue is battery voltage

    So voltage coming through the IG1 Relay to the fuses to the motors appears fine. The mystery is how voltage is coming down the thin blue wire when the car is off and why the DOME circuit has anything to do with that.

    Also, the wiper stick (combination switch?) is on the steering column so the clock spring shouldn't have anything to do with it?

    IMG_7131.JPG IMG_7132.JPG
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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  16. valde3

    valde3 Senior Member

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    Does pulling the 15a RR WP fuse stop the drain? If yes then maybe bad rear wiper relay? Very unlikely but very easy to test.

    If no. Unplug the connector for the wiper stick. If drain is still there you can check the voltage at the connector to know if the fault is in that wire or in the other wire that is connected to it with diode. After that (or instead) you can also unplug it at the connector where the diode is.

    Then you will know exactly the peace of wire the problem is in. After that you can look through wire routing to find the spots to check for the actual fault. You can also do simular checks on dome circuit to find the fault location on that if finding the fault seems too hard otherwise.
     
    #16 valde3, Dec 22, 2019
    Last edited: Dec 22, 2019
  17. djimbuser

    djimbuser Junior Member

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    I had "RR WIP", "WSH", or "WIP" all removed and there was still voltage on the Lt Blue pump wire with the car off. I've looked at tracing that Lt Blue wire back to other points but that seems pretty involved to find connectors such as "IA2" (near driver door mirror buried in dash) and (5I/N/H/C aka "Center Connector No. 2 Inner Circuit") .

    By "Wiper stick" you mean the rear wiper motor? I can certainly do that.

    According to the wiring diagrames here's everything DOME powers so chasing that around would seem really difficult: ABS, TRAC and VSC, Air Conditioning,, Automatic Glare–Resistant EC Mirror, Automatic Light Control, Back–Up Light, Clock, Combination Meter, Cruise Control, Door Lock Control, Engine Control, EPS, Garage Door Opener, Headlight, Headlight Beam Level Control, Interior Light, Key Reminder, Light Auto , Turn Off System, Luggage Compartment Door Opener, Multi–Display and Audio System (Built–in Amplifier), Multi–Display and Audio , System (Separate Amplifier), Power Window, Push Button Start System and Hybrid Vehicle Immobiliser System, Rear Window, Defogger and Mirror Heater, Seat Belt Warning, Shift Control System, Smart Key System and Wireless Door Lock Control (w/ Smart Key System), SRS, Taillight and Illumination, Theft Deterrent, Tire Pressure Warning System, TOYOTA Hybrid System, Wireless Door Lock Control (w/o Smart Key System)

    I can't help but consider that other oddity: When the dome fuse is removed and the car is ON, the rear wiper motor is stuck ON... seems like they'd be related.
     
  18. valde3

    valde3 Senior Member

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    So it's not feeding through wiper motor relay and its fuse.

    No I meant the combination switch where you control the wiper and washer. But with the knowledge that rear wiper is on when car is on maybe the problem is that the black wire going from pin 6 of rear wiper relay to A pin 7 of combination switch is touching the wire that is connected to gauge fuse. And it would be back feeding through rear wiper relay.

    Very easy test to do is to turn the rear wiper switch to full speed when the car is OFF. Battery current should go up a lot if I'm right about where the fault is. Or current might go up so much that it would burn something (fuse likely) and then the drain would stop.

    Another possible problem would be in between rear wiper motor and rear wiper relay. You can easily check for that by measuring voltage at the rear wiper motor when car is OFF. No wire should have any voltage.

    After you finally find the faulty wire all you need to do is to find where they are touching. You can make it easier to find the spot by disconnecting the circuit at the connectors in between until you find two connectors that the fault is in between. Also you can (temporarily / hack way) fix the problem by disconnecting that wire from both ends and running a new wire to connect it back together. Correct way of course is to find the exact spot and just fix it.
     
    #18 valde3, Dec 22, 2019
    Last edited: Dec 22, 2019
  19. edthefox5

    edthefox5 Senior Member

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    Pin 1 of the rear motor is directly connected to battery via 20 amp WASH fuse then via junction connector J7/8 to the pin 1.

    Pin 1 of the front washer motor is directly connected to battery via Same Fuse via junction connector J7. to Pin 1.

    So you should have 12 volts on both pin 1's. I know you do because the rear washer motor was running all the time killing your battery.

    Both pin 2 's should show open if combo stalk off. Turn on Combo swx stalk for either and they should show dead short to ground on Pin 2
    when combo on. Off=Open.

    There no floating there either meg ohm open or dead short depending on combo swx being on or off. if you see a short on Pin 2 with combo swx off then start checking the J7/8 junction block for corrosion or diode. See below for diode.

    You can clearly see this in your print including the switch position of the Combo swx for both motors.

    BE aware there is a diode across PIN 2 and ground on the REAR washer motor! Both the junctions blocks J7/8 and that diode called D18 are above the fuse box by your left knee in the cabin just above the left vent. I suspect D18 is shorted.

    If you measure PIN 2 of the rear washer to ground with plug unplugged from motor and the combo swx off and its low ohm I would highly suspect that diode is shorted.
     
  20. djimbuser

    djimbuser Junior Member

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    Hey Ed, thanks so much for your efforts to help me.

    Both Pin 1's of both motors go to 12V when I turn the car on and back to 0V when I turn the car off.. which is normal functionality.

    Pin 2 of the rear washer motor is the problem. When the car is off Pin 2 rear washer is battery voltage (and the front washer is 0V on Pin 2).

    I disconnected the connectors from the combo switch and measured the Light Blue wire and it was also battery voltage with the car off.. but so was the black wire (wiring diagram shows this goes to pin 7 of the combo switch)

    So it would appear that the car would be applying reverse voltage to the rear washer with the car off & motor connected.

    I have seen those diodes on that connector panel above the fuse box. I had to remove that metal plate with the three nuts securing it. There appears to be three diodes. I'll investigate those more.

    One other thing I'd like to note at this time is I did some snooping at the rear WIPER motor in the back. I disconnected the connector to the relay and found battery voltage on Pin 6(BLACK). This seemed consistent with finding battery voltage at pin 7(also black) at the combo switch. When I disconnect the Wiper Motor, the black wire at the relay goes to 0V but the black wire at the combo switch is still 12V. This is just getting more confusing all the time! I took a video of this: