Climate control display inoperative when lights on - Toyota Nation Forum : Toyota Car and Truck Forums
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post #1 of 3 Old 02-19-2018, 03:35 AM Thread Starter
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Climate control display inoperative when lights on

I'm in the process of replacing a switch for the NAV lockout mod in my 2014 Limited. I previously had an unlighted switch installed, with the vehicle speed sensor running though it. Everything worked great. I wanted to install a lighted switch instead, and was getting everything ready (switch and relay). No connections had been made, because I didn't know which 12v ignition source I was going to use yet. I was testing some of the harnesses under the center console to find the wire for the rear DC outlet. I think I found it in a white connector under the rear cupholder by the shifter. I found a dash light source in an unused plug by the "Snow" button, which I think is for an AWD model (mine is not AWD). Anyways, as I was testing the connectors with my multimeter, I noticed with the ignition "on", that when I turned my lights on, the climate control display goes out. When I turned my lights "off", the display came on. Same with the lighted switches to the left of the steering wheel,the traction control, snow, and even the window switches. All other lights work appropriately (including steering wheel switches). The climate control system works normally, but with no display with the lights on. The same with the rear climate control display. Is it possible I blew a fuse somewhere? I didn't arc anything that I know of. I checked the fuses I thought may be linked to it, but have not had any luck so far. Everything appears plugged in. Anyone run in to this issue before? Any help steering me in the right direction would be greatly appreciated.

Dave
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post #2 of 3 Old 02-19-2018, 05:42 PM Thread Starter
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Narrowed it down a little further. The climate control display and switch backlights (switches to left of steering wheel, in front of shifter, and window switches) go out when headlights or parking lights are on, but only when solar sensor "sees" that it is dark. Meaning, in daylight, with headlights on, everything works normally. Cover the solar sensor, and in about 5 seconds, the climate control display and switch backlights turn off. The climate control still functions normally, as do the other switches. They just have no display or backlight. The gauge cluster display and steering wheel switches, with dimmer functionality, are unaffected.
Does anyone have a diagram of the dimmer system and the lighting system that incorporates the solar sensor? What BCM controls this, and where is it located?
I have checked all fuses, and Techstream sees no issues so far. I can play with Techstream a little more to see if there was anything I missed.

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post #3 of 3 Old 02-26-2018, 12:48 AM Thread Starter
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I've been researching this more, even getting a subscription to TIS to look at the wiring diagrams and FSM. My clock display is also out anytime the light switch is on anything but "off", regardless of the solar sensor sensing light, but it maintains time perfectly. All window switches, except the driver's master switch, have working backlights. Looking at the "illumination" wiring diagram, every switch backlight negative (including the illum functions of AC displays and sunroof switches) go through the clock. The positive wiring goes through 2 fuses and the taillight relay, then to the Main Body ECU (BCM), except the clock positive goes straight to the BCM . I've checked continuity from clock harness to harness UF1 (rear console box), which would encompass, I think, most other affected items. The only test for the clock in the FSM is to hook battery power to 2 terminals to see if the security indicator lights. Mine does. I don't know if this tests the rest of the clock's internal circuit, specifically the illum circuit. I have battery voltage of 12.XX volts at UF1's red (positive) wire with ignition on, and about 9.5 + volts on UF1's white (negative) wire. The 9.5 volts goes up by ~.05 volts with each DECREASE in dash dimmer step. I tested it at the UF1 because that is the furthest connector from everything else, so I can assume the rest of the circuit gets it, too (I think).
Does anyone know of a way to test the internal illum circuit of the clock? With my Nissan vehicles, the FSM has very specific testing procedures and specs to test electronic circuits for these things. The Toyota manual does not list one (unless the security indicator one actually tests the entire circuitry inside the clock, but I don't know).
Interestingly, the illum circuit for the switch backlights, clock, and AC displays do not include the dimmer switch in the combination meter. I guess the combination meter dimmer goes to the BCM, and the signal is sent from there (which apparently works, because my voltage changes with each step of the dimmer switch). So I'm leaning towards either the clock or the BCM being bad. I just don't know which one, and would rather not spend a bunch of money on the wrong part.
Techstream reports no DTC's.

Any ideas would be greatly appreciated.
Dave
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