Auto Headlights always on, light/rain sensor failure? 2018 CX-5

[ruthrj]

Hello all,

I noticed my mother-in-law’s ‘18 CX-5 Grand Touring has the headlights on all of the time when “Auto” is selected (night or day). Just shy of 70k miles on it, and the windshield was replaced by Safelite a little over a year ago. No idea when the issue started, my mother in law just said her backup camera was really dim and her HUD didn’t show up anymore.

Today I took it for a drive and I realized it’s likely because the vehicle senses that it’s dark out. I overrode the HUD controls and can make that display just fine by adjusting brightness up in settings. Backup camera is indeed pretty dim in reverse.

Anybody have any experience with this issue? My instinct is to replace the rain sensor on the windshield. Nothing visibly wrong with it, it’s adhered to the windshield. The wipers also function normally with the auto sensing feature. No other faults I can see other than the vehicle sensing it’s dark all of the time.

Parts to replace? TK78-66-5G0A (sensor)
TK80-66-5G2 (sensor adhesive sheet)

The car also needs the screen lens replaced due to ghost touch issue, plenty of info out there for that procedure but I haven’t found any reports yet for auto-lights being on all of the time.

 

[yrwei52]

Are you sure the headlights on isn’t the DRLs? Verify it by checking out the rear lights which are also on if the light sensor is malfunctioning and turn the headlights on in Auto Mode.

BTW, the light sensor for Auto Headlights is on the top side of dash near the base of the windshield, not the rain sensor.

 

[hsdejong]

BTW, the light sensor for Auto Headlights is on the top side of dash near the base of the windshield, not the rain sensor.

Nope, that is the sunlight sensor for the automatic air conditioning/heating.
The camera behind the rear-view mirror measures the ambient light.

 

[ruthrj]

Are you sure the headlights on isn’t the DRLs? Verify it by checking out the rear lights which are also on if the light sensor is malfunctioning and turn the headlights on in Auto Mode.

For sure not the DRLs. The green headlight icon is displayed on the dash. The rear lights being on was what clued me in.

Nope, that is the sunlight sensor for the automatic air conditioning/heating.
The camera behind the rear-view mirror measures the ambient light.

This is my understanding as well. I found a pic in the owners manual to confirm, it says not to obscure the upper windshield or it will mess with the auto sensing feature.

I’ll likely fix the ghost touch issue first and go from there. The screen wildly going through menus on its own every so often could’ve screwed with a setting. I think that’s an unlikely cause but best to get that sorted first while I research further.

 

[yrwei52]

Nope, that is the sunlight sensor for the automatic air conditioning/heating.
The camera behind the rear-view mirror measures the ambient light.

My mistake, the Auto Headlights are using rain sensor as the light sensor to turn on the headlights automatically.

The High Beam Control System (HBC) uses Forward Sensing Camera (FSC) which also located at the center top of the windshield next to rain sensor to control automatic high beams.

 

[yrwei52]

For sure not the DRLs. The green headlight icon is displayed on the dash. The rear lights being on was what clued me in.

This is my understanding as well. I found a pic in the owners manual to confirm, it says not to obscure the upper windshield or it will mess with the auto sensing feature.

I’ll likely fix the ghost touch issue first and go from there. The screen wildly going through menus on its own every so often could’ve screwed with a setting. I think that’s an unlikely cause but best to get that sorted first while I research further.

Yes, you’re correct. The rain sensor is the light sensor to be used for Auto Headlights. Does the 2018 CX-5 come with optional ActivSense Package which has FSC to be used by HBC、Mazda Radar Cruise Control with Stop & Go function (MRCC)、Smart Brake Support (SBS)、etc.?

Looks like you can change the sensitivity of the auto-light control from settings on the center display. But since the windshield was replaced by Safelite a year ago, my bet is they used an aftermarket windshield which doesn’t have pre-glued bracket on windshield to hold the rain sensor properly. Some even reported the Safelite simply just taped the sensor on the windshield! You can open the plastic cover and check if the rain sensor was installed properly before you spend money for a new rain sensor which rarely fails.

In circle is the infamous T20 Torx bolt which is always loose causing the rearview mirror vibrates (mine is loose again). The rain sensor is the one with the letter “A” which is supposed to clip on the pre-glued bracket.

 

[yrwei52]

⋯ Backup camera is indeed pretty dim in reverse.

When the headlights are on, every display in the cabin will be dimmed?

 

[ruthrj]

When the headlights are on, every display in the cabin will be dimmed?

Correct. I think I overrode the dash and media screen brightness to compensate. All of the screens are super bright at night and have to be dimmed as a consequence lol. I’m thinking the dim backup display could due to its own independent setting, likely messed up by ghost touch.

I think the rain sensor is actually the top left module in that image, not the module with the A. I need to pop the cover off and investigate as you suggested. Bathroom reno is taking up all my time, damn cabinet installers popped the cap off a sink waterline and soaked a bunch of insulation and drywall this morning (facepalm)

 

[hsdejong]

In my 2023 CX-5, there doesn't seem to be a direct relationship between the headlights and the instrument cluster lighting, except that the ambient light plays an important role...

 

[yrwei52]

⋯ I think the rain sensor is actually the top left module in that image, not the module with the A. I need to pop the cover off and investigate as you suggested.

Yes, I believe you’re right. Not sure what is it for the one with an “A” in picture? These pictures are from my 2016 CX-5 GT with Tech Package without i-ActivSense Package. There should be only one rain sensor in there. And looks like the correct part number for rain sensor is TK79-66-570B which includes the pad.

 

[ruthrj]

But since the windshield was replaced by Safelite a year ago, my bet is they used an aftermarket windshield which doesn’t have pre-glued bracket on windshield to hold the rain sensor properly. Some even reported the Safelite simply just taped the sensor on the windshield!

Nailed it. Aftermarket windshield (Fuyao), and there’s no bracket. I thought I saw the sensor through the windshield but it wasn’t attached. Gel isn’t sticky enough to adhere to the glass, and there’s a couple gray sticky tabs that I think were original to the sensor lol.

Going to see if I can procure a bracket and glue it to the glass. There’s a YouTube video of a guy doing that for a CX-3 or 30. I’ll order a new gel layer for the sensor as that’s one time use.

 

[ruthrj]

Giving AliExpress a try for the pictured bracket. As I feared, can’t find a OEM part as it’s part of the windshield. The appearance is consistent with a 2019 bracket I saw in an eBay picture. Wish me luck!

 

[yrwei52]

Nailed it. Aftermarket windshield (Fuyao), and there’s no bracket. I thought I saw the sensor through the windshield but it wasn’t attached. Gel isn’t sticky enough to adhere to the glass, and there’s a couple gray sticky tabs that I think were original to the sensor lol.

Going to see if I can procure a bracket and glue it to the glass. There’s a YouTube video of a guy doing that for a CX-3 or 30. I’ll order a new gel layer for the sensor as that’s one time use.

Actually you can have your mother-in-law taking the case to Safelite and ask them to put a correct windshield on which comes with pre-glued bracket for rain sensor. Aftermarket windshield such as a one from Fuyao they should have the one like OEM windshield with pre-glued sensor bracket. From OEM they have at least 3 different windshields for different trim levels and optional sensors. I believe Safelite simply ordered a wrong windshield originally.

The problem for putting the bracket on by yourself is you may have a hard time to the find the proper position on the windshield, and how long the bracket can stay on the windshield with the weight of rain sensor. The workshop manual even calls a calibration step on rain sensor after the (OEM) windshield has been installed.

 

[yrwei52]

Giving AliExpress a try for the pictured bracket. As I feared, can’t find a OEM part as it’s part of the windshield. The appearance is consistent with a 2019 bracket I saw in an eBay picture. Wish me luck!

No, the sensor bracket(s) comes only with OEM windshield(s), not sold separately by Mazda.

AliExpress is a great place to find something which is hard to find or not available in the US (like problematic CX-5 power seat short and long cables) with excellent price. I just got wiper rubber inserts for all of my vehicles as the prices for OEM inserts from Mazda are outrageous right now. They cost $2 ~ $3 each instead of $10+ each from Mazda, and they all look exactly the same as OEM and fit perfectly. They wipe very clean and quiet during many raining days recently in Dallas area. The only thing I don’t know is the longevity. Only time will tell.

 

[MichalP]

When I was replacing my windshield in cx5 quite a few years ago they just reused the bracket from the old windshield. They did not glue it right the first time and the whole thing just fell off. Took it back and they fixed it for good. But that was small local shop here in Canada. I guess people working at Safelite were not smart enough.

Funny part. I was replacing at the same time windshield in my mazda 3 from 2008 and the shop pointed it out that this windshield despite being cheaper overall came with pre-installed sensor. Both windshields were aftermarket.

 

[ruthrj]

Safelite is a pain in the ass, lol. It’s been over a year (out of warranty), so I’ll go that route if this bracket doesn’t fit right. Seeing how they cut corners this badly with the windshield last time, I don’t want to have them touch the car again.

 

[yrwei52]

When I was replacing my windshield in cx5 quite a few years ago they just reused the bracket from the old windshield. They did not glue it right the first time and the whole thing just fell off. Took it back and they fixed it for good. But that was small local shop here in Canada. I guess people working at Safelite were not smart enough.

Yeh a good small local shop may not have sophisticated but expensive equipment to calibrate those sensors after the windshield replacement, at least they’re trying their best to make things right.

Funny part. I was replacing at the same time windshield in my mazda 3 from 2008 and the shop pointed it out that this windshield despite being cheaper overall came with pre-installed sensor. Both windshields were aftermarket.

That’s good to have the sensor ($$$) pre-installed making sure positioning is correct. Some sensors may need precise positioning on the windshield such as FSC Forward Sensing Camera, but rain sensor may not need that precision IMO. That’s why I didn’t bother to have the dealer doing the calibration on rain sensor like the shop manual stated after my windshield replacement which was also done by a local shop with an OEM windshield supplied by myself.

 

[ruthrj]

Some sensors may need precise positioning on the windshield such as FSC Forward Sensing Camera, but rain sensor may not need that precision IMO. That’s why I didn’t bother to have the dealer doing the calibration on rain sensor like the shop manual stated after my windshield replacement which was also done by a local shop with an OEM windshield supplied by myself.

If I’m reading the shop directions right, it’s applicable if you replace the sensor. Even then it looks like all you do is change the sensitivity away from medium and back to medium? I dunno, haven’t dug that far yet Mazda CX-5 Service & Repair Manual - Rain Sensor Removal/Installation - Wipers

 

[cz5gt]

new sticker is to be used when changing the windshield glass. The sticker is the gel type that makes the sensor work properly. Nothing wrong with the sensor. Its sloppy job by whoever changed the glass.. unfortunately.

 

[ruthrj]

new sticker is to be used when changing the windshield glass. The sticker is the gel type that makes the sensor work properly. Nothing wrong with the sensor. Its sloppy job by whoever changed the glass.. unfortunately.

I also have the adhesive sheet ordered from MazdaSwag. That should be here soon. I’m sure I’ll be waiting longer for the aftermarket bracket from AliExpress. That’ll give me time to choose an epoxy for the bracket