Got an alarm? Got a dog? Get some tape!

The optional alarm in a Sprinter is OK, but it’s hard to remember to turn off the motion sensor each time you lock the van. If your dog is asleep in the van, it’ll wake up and stretch while you’re away, making you unpopular with everyone around you.

The answer’s pretty simple – electrical tape over the motion sensors.

The factory alarm is set-and-forget. Once you lock the van with the key fob, the alarm activates. It has vibration sensors, a towing sensor, door opening sensors, and inside the van there are motion sensors too.

You can turn off the towing sensor and the motion sensor using buttons on the console above the rear view mirror. But you have to do this each time you leave the vehicle. You also have to do it just a short time before you lock the doors.

Sprinter alarm sensors and buttons

If, like us, you sometimes leave your dog in the van*, then it’s inevitable that you’ll fail to disarm the motion sensor at some point. The dog’s movement will set off the alarm, which will probably scare the dog, causing it to move around some more. Not a good situation.

We decided that since we’re disarming the motion sensors most of the time anyway, it would be better to just have them not work at all. The alarm still protects the van pretty well from break-ins because of the other sensors.

The low-tech way we did this was by cutting little squares of electrical tape, and sticking them over the motion sensors.

In our 170″ wheelbase van, there are three sets of sensors. One is in the console above the rear view mirror. One is immediately behind the cab area in the headliner, and one is by the rear doors pointing forward. Each sensor panel has either two or three motion sensors in it. They appear to be optical rather than radio frequency. The sensors are ultrasonic, but if they are blocked off with tape, they can’t detect any motion, so they’ll never trigger the alarm.


*Before anyone decides to send hate mail about leaving pets in vehicles, this van is better insulated and has better climate control than some houses. We also live and travel in temperate climates.

2 Replies to “Got an alarm? Got a dog? Get some tape!”

  1. Recent purchase of a Roadtrek on MB Sprinter. Starter battery went dead when not started for 2 weeks. After recharging took the RV into MB service to find out what was drawing down the starter battery. According to their diagnostics the mid and rear motion sensors were damaged or cut when Roadtrek upfitted the Sprinter. MB will not disconnect the system. So, naturally they expect me to go back to Roadtrek, which is not possible as they are currently in Receivership. They are probably located behind or above cabinets. Removing the cabinets and replacing the sensors and taping them would potentially alleviate this issue of draw down on the starter battery?

    1. Lois, it’s always sad to hear about upfitters cutting corners like this. Assuming that indeed the wires were cut (and let’s be clear, MB service is making an assumption there based on their diagnostics rather than on actually seeing the wire ends), then yes replacing the sensors *may* resolve the issue.

      The wires from the sensors run through the main wiring loom on the driver’s side of the vehicle at roof level. You’d need to work out whether Roadtrek just stuffed the sensors into the ceiling space above where they normally sit, or whether they cut the wires at some point between the sensors and the loom. My guess is, if they are in the business of just cutting stuff out, they wouldn’t have bothered to go any further back in the circuit than the loom itself.

      It’s also worth considering that Roadtrek may have wired something else entirely different into the starter battery circuit, and that this thing is the culprit for your power draw down. One way to see which aftermarket parts are running from the house battery and which are running from the starter battery is to disconnect the starter battery (connector by the accelerator pedal) and then check what does and doesn’t work in the Roadtrek part of the vehicle still. If they installed an aftermarket stereo, check whether that works without the key in – another potential source of constant power draw.

      I don’t know how the house batteries are charged on your vehicle, but it’s probably also worth checking whether the charging system is in any way attached to the alternator (and thus starter battery). RV companies often use cheap isolators which still draw current even when they are “open”. That would be a more likely culprit in my opinion.

      And obviously, until you’ve worked out what the problem is, a trickle charger is a good way to protect your starter battery from damaging levels of discharge.

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