After a rainy season my Han started behaving strangely in a way that tracked the weather. Door handles stuck. The car reported a door not closed when it was shut tight. Cruise control stopped working. Interior lights stayed on. At one point the system believed I was pressing the brake and the accelerator simultaneously, and the brake lights stayed on until everything dried out.
Every one of those cleared up as the car dried. That pattern is the useful part: if faults come and go with the weather, you are probably looking for water and connectors rather than for the components that are throwing the errors.
What happened, in order
The rainy season arrived and the door handles started sticking.
Then things started failing that have nothing to do with a door handle. The car reported a “door not closed” message with the door shut tight. Cruise control stopped working. The interior lights stayed on. And once, memorably, the car decided I was pressing the brake and the accelerator at the same time, and the brake lights stayed on until everything dried out.
I filmed two of them, on 12 May and 12 June 2025, a month apart, both in the rain, because a description of this reads as exaggeration until you see it:
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Nothing loads from YouTube until you press play. If you do, the player is served by Google, which can then set cookies and log your IP address.
The second one is the more useful of the two. The car is telling me I am on the brake while the power meter reads 31 kW going out of the battery at 47 km/h. Both of those cannot be true, and only one of them is measuring anything.
And the order matters, so let me be straight about it: the handle was not replaced until late August, three months after the first of those recordings. When I first wrote this up on Reddit I put the repair before the faults. That was wrong. The faults came first, the part swap came second, and the part swap did not change them.
Not a single one of those is a door handle fault. They are all things downstream of a door handle, on the same electrical neighbourhood.
Why a door handle takes cruise control with it
I am not an automotive electrician and I am not going to pretend to diagnose this properly. What I can say is what the pattern suggests, and it is the same thing any experienced person will tell you: when unrelated systems fail together and recover together, look for something common to all of them.
On this car my working assumption is corroded connectors. That is an assumption rather than a diagnosis, and I want to be clear about which it is. Nobody has shown me a corroded connector. What I have is a set of faults that appeared with water, moved around, and disappeared when the car dried.
The reason it is worth writing down anyway: a service centre presented with “cruise control has failed” can spend a long time on cruise control. Presented with “five unrelated things fail when it rains and recover when it dries”, the conversation should go somewhere different.
Water in the cabin
Separately, about a year ago I found water getting into the cabin.
I fixed the leak myself in the end. The service centre had not found it, and I had pointed it out to them.
I am deliberately not claiming a connection between the leak and the electrical faults, and I have not claimed one anywhere else either. I do not have the evidence for it. What I will say is that if you have water entering a cabin and electrical faults that follow the weather, treating them as two unrelated tickets seems optimistic.
What I would do differently
If your car develops odd electrical behaviour, write down two things every time: the symptom, and the weather.
That sounds trivial. It is the single most useful thing I did, because after a few entries the pattern was obvious, and a pattern is far harder to dismiss than a complaint. “The cruise control is playing up” invites a shrug. “These five systems fail when it is wet and recover when it is dry, here are the dates” is a different conversation.
Photograph anything visible before anyone touches it. And if you can, check the obvious water paths yourself. I found my leak, which is not a boast: it means it was findable.
The part that still sits badly
The handle that started all this went in working. It came back replaced. And the electrical faults it was supposed to account for had been happening for months before anybody touched it.
I have written up that sequence properly in the post about the 12V battery, because the same visit is where the battery ended up flat and where the workshop spent weeks on something an owners’ group answered in a minute.
Five years and 50,000 km, and the car still drives beautifully in the dry. That is what makes this frustrating rather than simply disappointing.
Has anyone else had weather-tracking electrical faults on a Han? Specifically: did anyone get a proper diagnosis rather than a part swap? I would like to know it is possible.
FAQ
Can rain cause electrical faults on a BYD Han?
On mine it did. After a wet season the car reported a door not closed while shut, cruise control stopped working, interior lights stayed on, and once the system read the brake and accelerator as pressed together with the brake lights staying on until things dried out.
Do the faults go away when the car dries?
In my case yes, which is the most useful diagnostic clue available. Faults that appear with water and clear as it dries point at moisture and connectors rather than at the individual components reporting errors.
What causes it?
My working assumption is corroded connectors, and I want to be clear that it is an assumption. Nobody has shown me a corroded connector; what I have is a set of unrelated systems failing and recovering together with the weather.
My BYD says a door is not closed when it is closed. What should I check?
On my car that message showed up in wet weather, alongside other electrical faults, months before the rear door handle was ever replaced. It tracked the weather rather than the repair. Worth recording when it happens and in what conditions before assuming the door sensor itself is at fault.
Does water get into the cabin on a BYD Han?
It did on mine, found about a year ago. I traced and fixed the leak myself after the service centre did not find it, though I am not claiming that leak caused the electrical faults.
What should I tell the service centre?
Bring a log rather than a symptom. Record each fault with the date and the weather. A list showing several unrelated systems failing when wet and recovering when dry is much harder to answer with a single part swap.
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