E350 Coupe Parking Sensor Fault - Sun??

[johny5_uk]

My parking sensors have been playing up the past few days but only when its hot and sunny.
My car is black so I guess it kicks off a fair amount of heat (you can see the rays off the bonnet) and I thought its maybe the heat triggering the sensors?They have gone off on their own when it has been raining and I thought that this was normal as the rain would trickle over the sensor but the heat with ultrasonics? would this cause them to randomly beep?
If so, I would hate to own this car in a hot climate! what would be the point of parking sensors.

 

[BlackC55]

I doubt the temp and rain causing the issue. You probably have a one or more faulty sensors.

 

[johny5_uk]

Really? I would have thought when the rain slide/drips over a sensor (or a couple of sensors at the same time) it trips it off?
Surely the sun/heat waves trip them off as well??

 

[whitenemesis]

If this was the case I'm sure it would have been highlighted before now?

Get it on STAR and read the error codes

 

[johny5_uk]

Yes, my car has been in the workshop for other issues so you would have thought the techs would have mentioned something? But then again, how would they tell if it were false triggering?

I am sure the rain and sun/heat rays have an effect on the sensors, hoping someone on the forum has similar results....

 

[whitenemesis]

Well I have parking sensors and have never had issues with hot sun or rain.

Have you checked they are clean and free of wax?

If they go off regularly when it's wet could it be a bare wire or exposed connection?

 

[johny5_uk]

I wonder if its the way the shape of the new e-coupe affects the rain.
For instance when it was raining the front sensors (left or right) would come on when I started braking, so I imagine this was when the water from the bonnet was trickling over them.
I will have a look tomorrow and maybe try with a jug of water.

 

[whitenemesis]

Keep us updated..

I would get back to the dealer and simply ask them to sort it..

 

[corned]

The parking sensor system is de-activated above a certain speed (on the assumption that you re not likely to approach a wall in close proximity at 30mph), is it not?

So if the system is activating when braking - at what speed? If it happens at much above walking pace, then it sounds like a possible electrical problem with the system to me - star will tell you.

 

[johny5_uk]

It is only triggering incorrectly when raining and I pull up to a junction (hence the thought of rain flying down the bonnet channel) and also (more rare) when the sun is belting down and the body of the car is very hot (you can see rays coming off the black paintwork). All other times it seems to work fine.

 

[corned]

Are they detecting a phantom presence, or are they warning of failure? There are two different types of alarm.

Either way, the warranty should cover it. It's for the dealer to sort.

 

[johny5_uk]

Just been checking them by pouring water over the fronts (it is only the fronts that seem to error) and the water has no affect when I pour over them so I take it rain shouldnt affect the sensors at all? I presumed that heavy rain would and thats why there was a button to turn them off but I guess I was wrong?

I went for a ride and sure enough after sitting at lights for a few mins, as soon as I set off the front right and left triggered randomly. When they trigger they come on full with a long beep. Now that I have mentioned it on the forum, this morning they have been going mental! I move forward then stop, when moving forward again slowly they trigger.

I do wax the car, so I have just used a tissue to make sure all the wax has been removed from them and see how it goes. Surely if the wax was affecting them the rears should also kick off randomly after I have selected reverse but they are fine?

 

[johny5_uk]

It is worse in the rain, just went out and the fronts are going off a good en.
When I pulled up the front right LED's stayed on so I got out and wiped all 3 right sensors, this didnt turn the LED's off but tapping them did.
Will call MB and get it booked in

 

[ohmsmowers]

My 10 plate E350 CDI coupe does the same thing in the rain, the front sensors tell lies all the time. The dealer says that this is standard. also flies affect it big time in the summer.

 

[johny5_uk]

I thought I updated this thread as my sensor fault had been fixed but I must have mentioned it in another thread.

Anyway, the fault was due to the number plate housing, it was mounted upside down!
Both the front and rear number plate carriers are like a plastic housing that pops open up and down and then the number plate sits inside it so no screw holes.
This mounting due to it being installed upside down actually affected the line of sight for the front sensors. It was raised only by about 10mm.
If you look at the housing it should have a thicker plastic band at the bottom but this was at the top. They mounted it the right way round and rain (heavy or not) and shine the sensors work perfect now.

If you don't understand the above, I can take pics. The sensors should work no matter what and since the housing was corrected (which I was sceptical about) mine have been perfect.

 

[Clogdiver]

I thought I updated this thread as my sensor fault had been fixed but I must have mentioned it in another thread.

Anyway, the fault was due to the number plate housing, it was mounted upside down!
Both the front and rear number plate carriers are like a plastic housing that pops open up and down and then the number plate sits inside it so no screw holes.
This mounting due to it being installed upside down actually affected the line of sight for the front sensors. It was raised only by about 10mm.
If you look at the housing it should have a thicker plastic band at the bottom but this was at the top. They mounted it the right way round and rain (heavy or not) and shine the sensors work perfect now.

If you don't understand the above, I can take pics. The sensors should work no matter what and since the housing was corrected (which I was sceptical about) mine have been perfect.

Randomly found this article because my E350 does this in the rain. I noticed that my number plate mounting is loose so thanks for the tip. I will check it tomorrow. I was going for more expensive diagnostics but you have have just saved me !!

Thanks