My (new to me) car has those little round sensor things in the rear bumper but I’m yet to hear any beeping when I reverse. Would anyone know if they could just be blanking plugs in the holes?
Thank you.
They should work if there, it was an option so not dummy sensors.
Perhaps they are working but the sounder has become unplugged. Check behind that black plastic trim panel in the boot. All the gubbins for my sensors on the last NC were positioned behind the left and rearmost panels inside the boot, the rear panel being the one with the boot light attached.
Thank you. I’ll have a look in there tomorrow.
It maybe that the sensors installed are no longer connected or the controller is faulty, they may well be after market ones; I’m not sure if they were ever an option from new.
You should be able to follow the wires coming from the sensor i.e. from under the rear of the bumper then into the boot area, maybe there is a clue at the end of the wires?
After market sensors are pretty cheap, indeed I have just bought some from Hawk Alarms for around £25 and they seem simple to fiit pending it not being so wet and cold when I will fit them. I have used Hawk products before and they are pretty good in my view, MX5 Parts also sell similar. See Hawk link below:
Roy
So I took some panels off in the boot and found this. I haven’t found the actual system yet. Should this red wire (currently disconnected) be connected to the yellow/red one where the tape was?
Thank you!
It looks highly likely that’s the problem. Looks a shoddy piece of cable connecting.
Just trace where those wires go to, guessing the red/yellow is the reverse light circuit and the red should be tapped into that.
Well it’s been a frustrating afternoon. I took the time to reconnect those wires properly to find that the thing beeps constantly when reverse gear is selected. Obviously tested with nothing behind the car. I was unable to find the unit itself as it goes way past the sides, past the petrol pipe and beyond. I didn’t have the time to take it all apart. Any tips here appreciated.
Having put the plastics back together I noticed the driver’s side reverse light is not coming on. I was going to say “I hope it’s the bulb” but if I’ve understood correctly I might have to take the light unit out to find out …
I bought the car off a dealer hoping there would be no problems with the car but so far it’s not proved to be a worthwhile added expense. Some would say I should take it back to get it sorted but I just don’t trust them. I already had to go back to complain about the unmatched tyres and the poorly attended stone chips which I ended up sorting myself. Lessons learned.
They only have one reverse light, that’s left side. That position in the light cluster on the driver’s side is for the rear fog.
Ah Ok. Thanks for that. I’m learning by the minute. The right side looked clear to me. I imagine there’s a red bulb in there?
MickAP is correct for UK car about the fog light, bigger bulb than the reverse light too.
The reversing sensors work by bouncing an ultrasonic signal off something. If the echo is less than so much it beeps, really close is continuous. If one is faulty then beep is likely to be continuous. On my kit each one has a “waterproof-connector” to plug into the black wired loom outside the car, and then the loom has plugs for the individual sensors going into the control box inside.
Here is how I installed mine and the pic show the usual type of control box and its typical connections and where Mazda expect it to go, I later moved the beeper closer to my ears.
The red/yellow wire is for the reverse lamp, black is it’s ground (apologies if you know that). If the red wire is for the sensors, have you checked that colour match under the bumper?
Here is a link to the US spec cars wiring diagrams - you need back up light. [Wiring Diagram - Body Accessories]
My thanks to everyone who replied. When the unit is connected there is a continuous beep when selecting reverse. As suggested there seems to be a fault, possibly a sensor. It has been too cold to work on the car so for now I have disconnected the red wire. Next job will be to see if I can determine if any/which sensors are faulty and also track the location of the unit which needs all of the panels to be removed. It may be easier to purchase a new unit.
Found a picture of the control/junction box for my old NC reverse parking sensors. You’ll have something similar hiding behind the panels. The numbers 1-4 are obviously the individual sensor positions at the box.
This is great! Thank you. Last night I got as far back past the petrol pipe and still didn’t manage to get to the unit. I need more time to take all of the panels out. I have at lease confirmed it’s dry there 
See link below and take a look at the HRA 6400 Series Installation Manual i.e. the one I referred to in my earlier post. Most makes work roughly the same with connections as per below and shown in the attached Hawk Manual
Unit power - Gnd + 12v from the Parking light wire.
4 Sensors - probably just a cable for each sensor that plugs into the controller.
Speaker - 2 wires as normal speaker.
For all the fiddling you need to do it may just be easier to remove the old system and replace with say a Cobra unit as per MickP, Hawk unit or similar from MX5 Parts that way you know what you are dealing with.
I recon your fault could be any of the sensors or the control unit, probably by unconnecting each sensor at a time you will get to work it out.
Roy
Thanks for that. A new unit will be on order later today ready for my next free day to install it. You’re right of course. The cost of complete new unit is relatively low and easier than repeated delving and fault finding under there.
You do still need to fully disconnect the old unit however in order to make sure it or it’s wiring does not cause other issues, especially with view to the fact that the installer simply twisted the wires and just used insulation tape.
It might pay you to hold back on your order until you have looked at the control unit and wiring, it could just be a dodgy/shorting connection based on the installed connection method???
I like to solder connections and use 2 layers of Heatshrink Sleeving (Heatshrink the first then slide the second over the top then shrink that), works for me.
I live near Gatwick, where are you? will you go to the East Sussex Downs meeting on the 29th in Bury?
Roy
Yes agreed. I have tidied that mess with a proper connector and also kept the sensor red wire disconnected. I’ll hold off doing any more till I have proper time to get behind the panels and find the existing unit.
I hadn’t noticed the Bury meet but have now put it in my diary and hope to be there. Really looking forward to meeting some members.
You need to book for the meet, best email ‘Chris Unstead’ and tell him you will be going and ask him for details if you don’t already have them. His Ownets Club email to use is as follows if you don’t already have it:
Roy
I didn’t answer your question - I’m in East Grinstead. Not far from you. Been thinking I might be best suited in the Sussex group.
