Rear Parking Sensors - Yet Again

[101RRS]

I have had my Mitch Hitch on for over 2 years and like just about every one else with one had issues with rear parking sensors. I have read just about everything on the topic and decided to go with the clear furniture protectors with 1/3 cut out which shields the side where the tow bar is but allows the sensor to work on the side away from the hitch.

I also read (and I cannot find the reference) that the outer sensors only have a short range (about 1.5m) and beam out to the side of the car and the centre sensors have a range of 2m and beam back and down so the real range is from the center sensors. I am also away of simply blocking the center sensors and rotating them away from the hitch but decided not to do this as the beam may no longer point rearward as it did.

I have had two instances last week where I have bumped things just as the alarm sounded and last night I collected my wheelie bin which I had put out it little too close to the driveway. Again the alarm sounded just as I hit the bin handle with the passenger side rear light cluster which has punched a small hole in the clear outer cover.

Today I tested the range of each of the sensors - as predicted the outers only have a short range and also cover the sides as well as behind. To my surprise the centers with the clear plastic covers with the cutouts only had a range of about 12" so the plastic covers, even with the cutouts.

So has anyone either swapped the inner sensors with the outer sensors (and their wiring) as the current outer sensor pattern is more suited to the inner position when a Mitch Hitch is fitted?

Or even more relevant has anyone just moved the inners further out on the bumper so the beam clears the hitch. Yes I can rotate them and I know how to do that but am interested in hearing of other options.

Oh - I suppose I have to buy a whole new rear light fitting rather than just getting a new clear outer cover.

Thanks

Garry

[shining]

I will also be interested in hearing what is possible.

[Graeme]

From the WSM...

After the initial detection of an object, if there is no decrease in the distance between an object and the central sensors, the time delay between the audible warnings remains constant. If an object is detected by one of the corner sensors only, the audible warnings stop after about 5 seconds if there is no change in the distance between the object and the corner sensor.


I would not swap inner and outer sensors however moving inners outwards will only affect the distance (calculated by triangulation) so you could learn to live with the variation, in the absence of being able to reprogram the module with the new spacings.

[SBD4]

I wonder...

one of the fixes for the rear wheel carrier was install a smooth material following the curve of the tyre to shield it from the sensors. I am guessing that because it was smooth none of the radar waves were reflected back to the sensors.

So, I wonder if a similar approach applied to the hitch would work.Perhaps a flat piece of metal installed at 45/135 degrees to the hitch and bumper in relation to the sensors would reflect the radar outwards rather than back at the sensors?

[Graeme]

Also from the WSM in case it helps with the design of a barrier.

Detection Calculation

When operating in the combined transmitter and receiver mode, the sensor outputs a number of ultrasonic pulses and receives the reflected echo signal. The parking aid module amplifies the received echo signals and compares them with a preprogrammed threshold to calculate the distance to the object. This is achieved by determining the elapsed time between the transmission and reception of the ultrasonic signal.

When operating in receiver mode, the sensor receives echo signals transmitted by an adjacent sensor. This mode is used to improve the accuracy of the system.

The detection cycle consists of the parking aid module operating one sensor in the combined transmitter and receiver mode and transmitting a number of ultrasonic pulses. The module then switches the transmitting sensor and the adjacent sensor(s) to receiver mode. After a short time delay, this sequence is repeated using a different sensor to transmit the ultrasonic pulse and continues until all four sensors have output an ultrasonic signal. This sequence is completed in 100ms. The module uses several measurements of the same sensors to remove errors from the calculation.

If the object is directly behind a sensor, the distance is calculated using the time between the transmission and reception of the signal. If the object is positioned between two sensors, the parking aid module uses both signals to determine the correct distance using triangulation.

To perform the triangulation calculation, the parking aid module must know the distance between the individual sensors in the bumper. This information is stored in the module memory. From the received distance from each sensor and using the known distance between adjacent sensors, the module can calculate the minimum distance from the vehicle to the object.

When approaching several objects, the module recognises the distance from the vehicle to the nearest object.

[101RRS]

Also from the WSM in case it helps with the design of a barrier.

Thanks Graeme - not sure I follow all that but reaffirms that stuff on landies often is more complex that it needs to be - I have a cheap $60 Chinese parking sensor system on another car and it works as well if not better than the one on my RRS.

What you posted does highlight that maybe the inner sensors should not be turned or covered as is the current practice when additions are provided on the rear end.

Cheers

Garry

[George II]

Sorry to come back to this topic , but have just taken delivery of my new D4 and am in process of swapping my Mitch hitch over from the D3 to the D4 - yes Have ordered the fitting kit from Mitchell Bros & done the 16mm upgrade . On the D3 I seem to remember that the inner sensors needed rotating 60 degrees (bit hazy on that as it was at least 5 yrs ago) . They worked fine at this angle for me esp as I tow a lot & backing up to trailers was still very accurate . (The solid tone meant you were within about 2cm of the hitch) . Only had a few out of character beeps when the ground went up at the back , like backing down a driveway & then up onto a road.
The D3 sensors were proud of the bumper ie raised ones. I notice the D4 sensors are a recessed type .
so what is the solution favoured by mitch hitch users on a D4 ? (I couldn't find mention of the clear furniture protectors elsewhere ???)
Has anyone got any pics of any modifications to address the parking sensor issue.
Thanks Again
Looking forward to doing battle with the top bolt for the M-Hitch when it arrives !!

[George II]

Fitted my Mitch Hitch onto the new D4 successfully a few days ago , Mitchell bros say in their fitting instructions for the D4 that you need to rotate the sensor 10 to 20 degrees . But the Sensors on the D4 are different to the D3 , you can't just cut another slot for it to fit into . The D4 sensors fit bodily into a housing that appears to be plastic welded to the inside of the bumper . Be Ok if you could just rotate the housing but doesn't look like you can.

Has anyone sorted this out for a D4 or RRS ?

I tried putting tape over part of the sensor - didn't work .
Tried making up a guard between the sensor & the towball (using a half section cut out of the top of a bucket ) - this had limited success but was very much in the way.
Removing the tongue & ball does work but again for someone who tows a lot its a pain.
I would like to do the small rotation if anyone can provide the tips on how to do it.

thanks
(Beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep !)

[d3viate]

As per past post on the subject, I have the Kaymar duel wheel carrier and Mitch Hitch, tried the adjusting sensors and the shields under the tyres submit to metal fatigue after a gazillion corrugations.
I fitted the black chair leg protectors to the sensors and it stopped my problems and the advantage for me is that the sensors still work when reversing in as I do everywhere I park, the sensors still sound approx a foot from whatever is behind.
The packet cost a few bucks from hardware stores.
I have my rear window covered in and no reversing camera, something I have been thinking of for years, but I rarely tow so I rely on the sensors and they have never let me down with the black chair leg protectors fitted for me.
They have stayed on for a couple of laps around Oz, seen the snow and tons of dust and corrugations but they hang in there.
They just cover the centre of the sensor.
Give it a go.

[pohm66]

Just had another member email me about my setup so thought I might as well share.

I used a mastic tape called coax tape Coaxial Cable Sealant Tape - 150mm Strip

[IMG][/IMG]

As it is malleable I was able to partially black out the sensors next to the Mitch hitch and has travelled really well over the last 3 years.