Radio recieving a lot less power after turning on headlights

[Biorno]

Hey guys, lately i've Been having this issue on my Toyota Yaris TS 2003, whenever i turn on the headlights it seems like power to the radio and most of the displays decreases. The radio also constantly pops as if its losing signal. I've tried to measure the grounds around the Battery but they're fine. Taking out the TAIL 7.5A fuse seems to do the trick but that disables some lights. Hope someone can help me with this issue.

[Stivino]

It could be that it has a "night mode" where it dims the display when you put the lights on.  It might be adjustable using the scroll through menu.

[Biorno]

The displays are not so much of an issue. I care more about the radio and nothing that i've done so far seems to have helped

[Cyker]

I wonder if there is a corroded wire somewhere or the alternator has issues...?

[Biorno]

I was wondering if anyone has the whole wiring diagram for this specific model, would really appreciate it.

[APS]

When does it dim the display? When you turn on just the sidelights, or dipped, or full/hi?

Sounds like a ground issue somewhere. But that somewhere would likely be under the bonnet, where things are more likely to corrode.

[Derek.w]

I start by checking all grounds from Battery.altinator & lights remove & clean is best also take note if you see wire corosion that you suspect then try a flying ground as a tempory wire.

[flash22]

It's a weak Battery voltage only tells you so much, you can get perfect voltage, it doesn't mean it can handle the current, as the current rises the voltage drops if there is not enough capacity you get all sorts of wired faults the lights are a symptom not the cause

Go and get the Battery and alternator checked properly

[bathtub tom]

Is this an after-market radio that could possibly have been connected to the supply that reduces the lighting level when the lights are on?

[flash22]

Silly question, make sure you haven't knocked the dimmer (LH stalk iirc)

[Biorno]

4 hours ago, APS said:

When does it dim the display? When you turn on just the sidelights, or dipped, or full/hi?

Sounds like a ground issue somewhere. But that somewhere would likely be under the bonnet, where things are more likely to corrode.

It dims when any of those you named are turned on, i was hoping it isnt under the bonnet but i guess i'll have to check it. By the way, do you know at least how many grounds are in the ts '03?

[Biorno]

2 hours ago, bathtub tom said:

Is this an after-market radio that could possibly have been connected to the supply that reduces the lighting level when the lights are on?

99% of the electronics in the interior are stock.

[APS]

1 hour ago, Biorno said:

It dims when any of those you named are turned on

Well, that's a bit suspicious. That means it dims even when just the side lights are switched on. Are you sure this is not just 'as designed'? i.e. the radio/trip computer display dimming when you switch the lights on.

I don't have a wiring diagram. Access to Toyota tech docs can be found at www.toyota-tech.eu. It costs a couple of quid for a few hours access but all the content can be saved as downloadable .pdf's

We have a completely factory standard 2003 T-Sport (UK spec, Japan-made). If there's anything you want to compare, just let me know.

[flash22]

I would check the dimmer on the stalk, they get left in the same position for years and can go intermittent or high resistance

[Derek.w]

8 hours ago, flash22 said:

It's a weak battery voltage only tells you so much, you can get perfect voltage, it doesn't mean it can handle the current, as the current rises the voltage drops if there is not enough capacity you get all sorts of wired faults the lights are a symptom not the cause

Go and get the battery and alternator checked properly

The voltage will also drop if you can measure it under load conditions or use a jumper cable to rule out voltage drop of radio ground then live then switched live.

 

[Andrei07]

On 6/20/2023 at 6:49 PM, Biorno said:

99% of the electronics in the interior are stock.

Hi Biorno, 

I have exactly the same problem and I would like to know if you have found the cause of the problem?
 

Thank you in advance.

[Andrei07]

On 6/20/2023 at 2:52 PM, flash22 said:

It's a weak battery voltage only tells you so much, you can get perfect voltage, it doesn't mean it can handle the current, as the current rises the voltage drops if there is not enough capacity you get all sorts of wired faults the lights are a symptom not the cause

Go and get the battery and alternator checked properly

Hi,

I want to thank you very much for your comment.

I also faced this problem for a long time and it never occurred to me that the solution could be so simple - replacing of the Battery.

Afrer replacing of the Battery, the problem disappeared immediately. Thank you again!

P.S. sorry for my bad english, I'm writing this comment with the help of a translator.

 

[Andrei07]

On 6/20/2023 at 2:52 PM, flash22 said:

It's a weak battery voltage only tells you so much, you can get perfect voltage, it doesn't mean it can handle the current, as the current rises the voltage drops if there is not enough capacity you get all sorts of wired faults the lights are a symptom not the cause

Go and get the battery and alternator checked properly

Hello again @flash22,

the problem reappeared after a few days…🤯

I thought that maybe the alternator is not charging the Battery properly, but I checked this and everything seems fine..

Maybe you know what it could be from?
 

[flash22]

at idle do the revs increase as you load the electrical system (lights, fog lights, heater blower on full, and rear defrost turned on?

is it all lights that dim inside and out? or just the inside ones

[Andrei07]

10 hours ago, flash22 said:

at idle do the revs increase as you load the electrical system (lights, fog lights, heater blower on full, and rear defrost turned on?

is it all lights that dim inside and out? or just the inside ones

Unfortunately, it's the other way around, when the headlights, air conditioner or others turn on, the revs drop.. 

Normally the revs should increase, correct?

What could be the reason that the revs decrease instead of increasing?

Thank you once again for your support..

[flash22]

the revs drop as the alternator is under load, does your car have a cable or electronic throttle? what engine do you have?

[Andrei07]

2 hours ago, flash22 said:

the revs drop as the alternator is under load, does your car have a cable or electronic throttle? what engine do you have?

My car is toyota yaris verso 2003, 1.3 petrol with engine code 2NZ-FE and it has cable throtte

[flash22]

I suspect your alternator is not producing enough current - so new alternator required