'22 Corolla Design Dipped Beams Stop Working in the Rain

[Lazarus_42]

Hi, this has beaten the main dealer. 

In heavy rain, with dipped & main beams on full auto, both dipped headlights go out. They always fail together, the dipped beams telltale in the instrument binnacle goes out at the same time and this fault leaves no error codes according to the dealership. I've touched no controls or switches.

If I park and wait they come back on which makes me think of water ingress that dries out with the heat of the engine.

It doesn't happen when I drive through standing water & it's not raining, it's  happened a couple of times at 5mph in a car park in heavy rain. These last symptoms cause me to think it's not getting in underneath otherwise standing water would do it. It's not getting in the front as it's happened at 5mph. I think it must be either the the valence at the bottom of the windscreen where the wipers are attached or down the side shut lines either side of the bonnet.

The main dealer in Ashford had a look for the fault but could find nothing.He said your dipped beams were very low (i'd had a heavy load in the boot) implying that I was so stupid that I couldn't tell the difference between low dipped beams & no dipped beams at all! I said that even if I was that dense it wouldn't explain the telltale on the dash going out when it happens. Then he tried to say that it's condensation "in the cold, damp air" & perfectly normal. I said that cold air holds less moisture than warm air &  LED  headlights run warm, not as hot as incandescent bulbs but warm nonetheless. That's why they need a heatsink. And anyway, it's always both at the same time. Condensation wouldn't be identical both sides. 

He then tried to get me to talk Motability in to changing the car early & he tried to interest me into an all electric new car!

I said i'd paid a £2,000 surcharge for the Design 2 litre Hybrid estate & that i'd factored in 5 year's use of the vehicle for that £2K "So no commission for you, me old mate!"

That's all the pertinent symptoms I can think of. Has anyone come across this before? I signed up to this forum just now to ask this question so "Hi everyone and thank you for reading this rather long question. I wanted to be thorough in giving you the best background information I could."

Apart from this problem I love the car to bits! It's made driving fun again even if I have to use hand controls. All the automation, radar cruise, lane keeping, auto lights etc have left me free to enjoy the handling & performance. When you select Sports mode and that 2 litre lump and the electric motor come in at the same time at full chat it sure puts a smile on my face!

Thanks again!

Laz 😎🚗💨💨💨💨

[yossarian247]

Hi, 

Could you perhaps try having the car parked and running with the lights on, then get something like a watering can and carefully pour some water over the edges of the bonnet near a light. Leave it a few minutes to see if it has an effect, if not move onto the other light, then to the scuttle etc. 

[Lazarus_42]

I suggested this to the dealership. They said they'd put a jetwash down every nook & cranny but couldn't get the fault to appear...

But you're right, I'll give it a go myself. After their squirming I don't trust them at all...

Cheers Yossarian! (That's some catch, that catch 22!) 👍📖

[yossarian247]

In the absence of anyone coming up with any clever suggestions, something else just occurred to me. What if this issue is actually being caused not by water as such, but by the wipers being switched on?

Does it literally only happen when the lights are on Auto and the wipers are on? I think the sensors for both the auto lights and auto wipers are up behind the rear view mirror. Could it be a weird earthing issue perhaps, where the auto light sensor is deprived of power when the auto wipers are on, causing the lights to cut off?

I may be barking up totally the wrong tree, but it might just explain how rain apparently causes the problem without there being any apparent water ingress, and jet washing not triggering the fault? When you park up and the lights start working again, could it be because you've turned the wipers off, rather than something drying out under the bonnet? Just a thought. 

[Lazarus_42]

That's an interesting idea. I'll add to that with a problem of moisture inside that triangular enclosure the freezes in cold weather & plays havoc with the auto dip of the main beam. 

Yossarian always did think outside the box in the book!

Cheers mate! Having moisture freezing in there points to you trouncing the mechanics at Steven Eagell Toyota (Ashford)! I've a service coming up at the end of the month. I'll keep you posted! I'd better let them sort it. Motability  is lease hire at it's heart and they may take a dim view of me romping in there with a hairdryer! 😆

Laz

[Lazarus_42]

Just sent them a link to this thread. It seemed easier than explaining it all to them over the 'phone or typing it all up again.

Plus yosssrian247 gets the recognition for what I'm thinking might be the answer. I could've ambled into the workshop with "I've been thinking, maybe it's... " but I'm not one to steal other people's glory.

🤔<- Actual image of yossarian247 in action! 😉

[yossarian247]

Well I'm very flattered, but it's only pure speculation on my part! I hope you get it fixed one way or the other. 

[Talking Hoarse]

I have a similar 2022 2.0 Design TS.  Sorry I dont have the answer. 

I gave up with auto dipping of headlamps very early on - I  found that, whilst  they usually dipped promptly when needed - eg oncoming traffic etc - that they were slow to return to full beam.  So I do this manually like old days.

However I have noticed in duller weather recently - with headlamps set to "auto" - that they sometimes come on for a while after travelling in shade of trees or buildings etc.  And of course they do not switch on if foggy or very wet.  This has led me to - if in doubt - switch them on manually and leave them on rather than risk being perceived as signalling to other traffic or whatever.

So the auto sensors and systems are far from perfect.  But - assuming that the rain and light sensors are indeed between mitrror and screen - I will have a scrupulous clean and peep next time I wash the car.

Cant say that these quirks stop me from enjoying the almost athletic nature of my car at all though.

[camellia30]

The rain light sensor would be my guess too.

I assume the dipped lights came back on in manual mode?

[Roy231]

at T.H. auto lights are a pain i have the same issue drive under a bridge or a tree shade and the light come on and go off the sensitivity settings make no difference wish the light switch had an off position like my last car, auto main beam same here too slow.

Can these auto settings be turned off with Carista ?