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Aftermarket Parking Sensors

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Gordon Colquhoun, Jul 14, 2018.

  1. Gordon Colquhoun

    Gordon Colquhoun New Member

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    Hi folks, more to this site so please be gentle. :)
    I'm looking for some help with an electrical issue I've come across whilst trying to fit front parking sensors to my 2018 GLA. I managed to get them fitted and used the fuse box under the passenger footwell as a power supply from one of the fuses, they work great, until I start the engine, then they just beep randomly like Morse code. I've used a relay to bypass any canbus issues and it still does it. Tried using different fuses and also running a power wire direct from the battery to power the relay but again, still sounds like Morse code. Is the electrics on new Mercedes not able to accept an aftermarket parking sensors kit? Thanks in advance.
     
  2. Westheath

    Westheath Senior Member

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    Empty garage, awaiting new toy :)
    Always use canbus friendly sensor kits.
    also ..............
    Make sure the sensors are fitted within the installation parameters range.
    Or ................
    They maybe picking up interference from another electrical source nearby whilst the engines running.
    If so .............
    Isolate the sensor wiring with extra earthing braded shielding or re-route the wiring run and sensor box.
     
  3. John Laidlaw

    John Laidlaw Senior Member

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    I didn’t think even poverty spec Mercs of 2018 vintage wouldn’t have front parking sensors ! Seems standard on most cars these days
     
  4. M80

    M80 Senior Member

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    Are these the type you might also fit to the rear?
    I've fitted the kits that are for front and rear with eight sensors. The fronts are supposed to initiate for 20 seconds after pressing the brake peddle (a flippin' nuisance of an idea), is it this type.

    If the first type then how are they initiated, as when fitted to the rear they would only be powered when in reverse. If yours are powered continually it's likely that the sensors are randomly picking up an obstacle.
     
  5. OP
    Gordon Colquhoun

    Gordon Colquhoun New Member

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    Parking Sensors that can be used for the rear can be used for the front. All you do is piggy back off a fuse and run a wire to a switch to power them on and off. Regardless if I use a relay to bypass canbus I'm still getting the Morse code beeping.
     
  6. M80

    M80 Senior Member

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    You seem to understand the canbus issue more than I can.
    Having gone straight from the battery, unless this kit is RF sensitive I don't see how the car can be causing interference bleeping, unless the senors are picking up an obstacle or faulty.

    I used a simple rear type kit for the front of Larisa'a Gr Cherokee. I favoured powering through a countdown timer, a couple of quids out of China. Reverse triggers the timer to supply the kit through its own relay. Larisa's is set to a 20 second countdown but can be adjusted up or down to suit. I can put in a switch to trigger if she feels it would be beneficial.

    Hot 12V DC Delay Relay Delay Turn off Switch Module with Timer 9934840552805 | eBay
     
    Last edited: Jul 14, 2018
  7. geraldrobins

    geraldrobins Senior Member

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    Reversing cameras seem to be more common on many new mercs with the omission of the sensors all round.
     
    John Laidlaw likes this.
  8. OP
    Gordon Colquhoun

    Gordon Colquhoun New Member

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    As explained earlier, the sensors all work fine with the engine OFF, so for them to go haywire when the enghine is running is very strange. It could be that the control unit for the sensors need to be as far away as possible from anything electrical. I can't think of anything else it could be.
     
  9. crippo2

    crippo2 Senior Member

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    you say you are using a relay. The relay should (will) have 2 power sources. One will drive the relay and the other will, through the NO and common relay contacts drive the load.
    Which are you taking from the battery? and what is the other supply you are using?
    try running the Sensor control box (SCB) from the car battery directly. If you still get interference when the engine is running, then there is a problem with the car battery supply, in/with the SCB or the connections to the bumper mounted units. Disconnect each sensor in turn. Does the noise go away? If so it is probably the battery supply to/return from the SCB box. To check this run the entire SCB and sensor system (suitably fused) from another battery. If that works then connect the 0v terminal of the second battery to the car chassis. Does this produce interference? if not then car battery +ve supply to the SCB is noisy. If interference returns either see your local vehicle electrical expert or install a noise suppression filter in the DRL box supply lines and try again - your car needs better suppression.
    I am assuming throughout that you have no separate display, just the beep speaker mounted in the SCB, that your SCB system is isolated electrically from the car, except for the +ve power inputs and chassis return and that all joints are properly made using cable of adequate capacity
     
  10. OP
    Gordon Colquhoun

    Gordon Colquhoun New Member

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    Thank you to eveyone who has ansered this post, it's given me some good points to consider. OK so here's my theory. Since the power connection I have made seems perfectly fine with the engine off and only causes issues with the ignition on I think it's safe to say the connections are all fine and the issue is possibly electromagnetic interference when the engine is running and all the electrics are powered up and in action. Since I have run a simple 2 core speaker type wire through the firewall from the fusebox under the passenger footwell it runs past the battery, fusebox with relays etc and an ECU before it reaches the control unit for the parking sensors. So here's my thought. If I replace the power wire that comes from the fusebox, through the firewall, past all the electrical components under the bonnet to the parking sensors control unit with a sheilded wire this should eliminate any electromagnetic interference coming from all the electrical components under the bonnet caused when the engine is running. Does this sound plausible? Am I better off extending the parking sensors wires into the cabin instead? Could each of the parking sensors wires be troubled with EMI aswell? What's the best solutiuon to have all the wires sheilded from any possible EMI? Thanks again folks.
     

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