Are tail lights, side markers, and orange side markers in the headlights lighting up when you turn on the headlights?

All of the interior button lights are not functioning? Like ALL of them?

 

Dome/reading lights, trunk lights, bottom door markers, tail lights, and head/running lights all are working. Also the small light in the storage area under the center armrest works.

Any backlight switch on the steering wheel, dash (aside from gauges) climate controls, hazard button, and seat heaters is NOT working.

 

All buttons get +12V from the battery when they should be ON, via Tail light relay, and #4 under-hood fuse. If tail lights work, I'm assuming that all buttons receive 12V as well.

Brightness is controlled by the duty-cycle grounding by the gauge control module. There is no separate fuse for that ground circuit. I would use a test light to check if buttons get 12V and ground.

If ground is missing, you can check the signal directly at that module. If not present, module is dead. It most likely uses mosfet / transistor for switching that ground, and if somebody really wants, it could be replaced if found dead. But that would require soldering.

The gauge control module is simply gauge cluster.

 

They do...Thankfully!

I get a voltage reading when I have the running lights turned on and test the button backlights. This is why I think it is either a bad ground or a problem with the dimmer.


Thanks for that insight. I'm seeing 12V when testing with a multi-meter the RED/BLK wire that goes to all of the backlights, as well as the dash-dimming switch (like I said before which shows 12V going to it through the RED and the RED/BLK wires). Interestingly, the dimming switch (+/-) controls the brightness of the gauge cluster just fine.

When you say the ground is missing, I'm interested in your opinion of where it should go? Are you suggesting the dimming switch is not getting ground? Really appreciate talking through this with me.

 

You wrote "They do...Thankfully!" but actually if they wouldn't it would be a cheaper and simpler fix.

Dimming switch is just a button. All it does is it sends info to the gauge cluster that certain button was pressed. Circuitry that does the brightness control is in actual gauge cluster.
It is most likely (from common sense, experience, and schematics) switched by a mosfet, which is a type of transistor, which is a type of switch. Think about it as a solid state relay that can switch on/off thousands (if not more) times per second.

Operation in simplification: it turns ON for let's say 1ms, then turns OFF for 1ms, then turns ON back again. That would give you 50% duty cycle, and since it switches really fast, you can't really see flickering, and bulbs appear to be at 50% brightness. If it would stay ON all the time, you have 100% brightness. If it stays ON for 1ms and OFF for 2ms you have 25% brightness, etc.

Here is a part of schematic where I outlined current patch for couple bulbs:



Technically missing G501 would cause the issue, but it's very unlikely that something is wrong with that ground. Most likely that "switch" (circle with arrow) failed.
You read 12V on red wire simply because it goes through incandescent light bulbs without load. Bulbs are just resistors, and with no load there is no voltage drop.

There is couple ways of fixing or working around the problem:
- replace gauge cluster - high price but right way of doing it
- fix the broken gauge cluster - not that hard assuming only the mosfet failed. Let's say low chance of working for low price if you can find it and solder a new (similar) one
- cut the "ground" wire going to gauge cluster, and ground it somewhere else - that would make all interior lights on 100% brightness all the time when headlights are on
- cut the "ground" and wire in-series resistor to limit the brightness, but that would also mean fixed brightness without adjustment, and resistor would need to be a decent value... 50W? One would need to measure the current and find resistor that could handle that load.
- rig some duty-cycle or variable resistance circuit to control the brightness independently of the gauge cluster settings

Last thing you could check is if you have ground (or 12V when headlights are ON) at gauge B9 red wire.

 

True - so true.

[QUOTE=peter6;16638001There is couple ways of fixing or working around the problem:
- replace gauge cluster - high price but right way of doing it
- fix the broken gauge cluster - not that hard assuming only the mosfet failed. Let's say low chance of working for low price if you can find it and solder a new (similar) one
- cut the "ground" wire going to gauge cluster, and ground it somewhere else - that would make all interior lights on 100% brightness all the time when headlights are on
- cut the "ground" and wire in-series resistor to limit the brightness, but that would also mean fixed brightness without adjustment, and resistor would need to be a decent value... 50W? One would need to measure the current and find resistor that could handle that load.
- rig some duty-cycle or variable resistance circuit to control the brightness independently of the gauge cluster settings

Last thing you could check is if you have ground (or 12V when headlights are ON) at gauge B9 red wire.[/QUOTE]

I follow your explanation. Since my gauge cluster is just fine, will your suggestions likely work for the main issue, which is all the backlights to other buttons do not work? I just want to make sure we are talking about the same area.

 

I'm not sure what you're asking. I feel like I'm repeating, but "button brightness controller", which is build-in into the gauge cluster, failed. It is internally in the gauge cluster and in normal circumstances is not considered replaceable item. It is not a separate module - just couple of components needed to achieve button dim function are soldered somewhere at gauge cluster's circuit board.

Gauge cluster might appear to be just fine because it works in 99%. Just that 1% is the button brightness control function, which is broken. That means that replacing the gauge cluster will fix your "no button backlight" issue.

I gave you couple other options, since I'm not sure what is involved in replacing the cluster in TL. It might need programming, it might display wrong mileage, and it will cost ~$100 for the used part alone.
At the same time simple mosfet is like $10 for 20 of them, 10 ohm 50W resistor is ~$10 as well.

 

I understand now. Thanks for the insight.

 

I have a suspicion this may be my issue.

 

Brown skid marks on a PCB are never a good sign.

If that is the same part: https://datasheetspdf.com/pdf-file/7...ectric/K1881/1 that is a N-channel mosfet.



To make sure that you have a right component, the right leg should be connected to ground (B10 connector if you look at the schematic), the back should be connected to the B9 red. Check where the traces go (to which pin) and check the plug's wire colors.

I can't really find it, but any similarly rated n-channel mosfet should do the job. For example might work.

 

Thanks a ton for the help. Do I still need that resistor if the mofset is the only thing I need to swap? I may have to get some of that copper wiring liquid (window antenna repair) to fix that connection. Getting a more precision soldering iron is going to cost me more .

 

If you replace that mosfet, you should be good without any extra parts. That is assuming nothing else is damaged, and that mosfet is in fact broken.

What is "copper wiring liquid"?

 

The liquid you can use to fix the rear-window defroster lines. Thats if more than the mofset is the issue. The board looks good otherwise so I'll keep fingers crossed and let you know. Thanks again!

 

I don't think traces are damaged, but if they are I would fix them with copper wire. Not with copper liquid.

By "more than the mosfet" I meant other circuitry, like whatever drives the mosfet, or whatever sends the signal to the mosfet to turn ON.
You could check that by connecting scope to the mosfets left leg, and looking for PWM signal changing depending on requested brightness, but throwing $10 in parts at it is low risk.

If you go to desolder it, heat it up nicely before you pull, so you don't pull it with the traces.

 

So I did a continuity test on the mosfet that looked burnt, and it is pin #10 (ground) and pin #18 and everything appears to be connected. Still no dash-button backlights.



Tried to follow #9 pin and it is going everywhere (in yellow), including a large heat-sink. Can't tell.which component might be causing the issue - not as easy to see as in the diagram.

Im almost ready to spring for a used dash kit for $60-80. I really hoped I could figure this one out. I know you made.other suggestions, but I don't want to have the lights on all the time. Open to any other ideas - I was hoping that MOFSET replacement would better connect the ground

 

Are there any numbers on that big mosfet (besides G6)? Two components on the right should be diodes - you could check them with multimeter diode test mode to check if they are still any good.

Connecting that red #9 to ground would cause dash lights to be on 100% brightness, but only if headlights are ON. If that is not acceptable then start looking for used gauge cluster.

 

Thanks for all the help. I can get an ohm reading off of everything but the one on the far right. Even though I want this to be successful, not sure if it is worth the effort. I went and bought a different gauge cluster, worked like a charm!

 

Problem solved then. Good.

There is only so many electrical threads where somebody actually fix and follow up at their problem.