Technical Parking Sensor Fuse Blowing

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Technical Parking Sensor Fuse Blowing

Heccie

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I've got a 2018 Doblo Maxi Pro 105. I recently took it in for its first MOT, which it passed fine, however on the way home I noticed a yellow warning triangle up on the dash. When I investigated it I found it also came up with a message "Parking Assist Unavailable". I could not confirm if the message was there when
I immediately started the van after the MOT was complete, so cannot throw it back at the garage and tell them to sort it out. I phoned them up and asked nicely if they could have done anything during the test that might have caused this problem. They denied that they had. Naturally.

I eventuall tracked down Fuse 49 (5 Amp micro fuse), under the dash, to have blown. Being an electrician by trade I have checked all wiring around the sensors and I found the parking control unit hidden behind the panel in the offside wall of the rear compartment, above the wheel arch. There is no sign of any damage anywhere that could have caused a fuse to blow. I replaced the fuse and it fixed the fault for a short while, but blew again as I stopped at a set of lights and applied the handbrake. I put in a slightly larger fuse (7.5A) to see if that helped. It lasted longer but still blew after a couple of hours.

I found a link to an online list of all the different fuses in the vehicle and it list F49 as supplying the following: Int. power for control panel lights, parking control unit, tyre pressure detector control unit, electric door mirror motor, rain sensor, electric top control unit, My-port infotainment socket. The van doesn't have most of those items, but the electric door mirrors still work with the fuse blown!!! so they are fed from elsewhere.

So, the question is: Is there anything else supplied by Fuse 49 that could be causing the fuse to blow, or is it only the Parking Sensor System? I noted that a new controller is well expensive and want to look at all options before trying to get one.

Also, anyone out there know if there is actually anything that an MOT test centre might have done to cause this problem, or was it just a bad coincidence?
 
After further investigation I found that the fuse also supplies the SatNav socket in the dash, but seems not to be related to the fault as I only found that out after a couple of weeks of not having it plugged in. What I did confirm, however, is that pulling the handbrake on is definitely what causes the fuse to blow. If I go on a trip and replace the fuse at the start it survives the whole trip, until I arrived and put on the handbrake a d it pops immediately. Time to get the van on the axle stands and get underneath!!
 
After further investigation I found that the fuse also supplies the SatNav socket in the dash, but seems not to be related to the fault as I only found that out after a couple of weeks of not having it plugged in. What I did confirm, however, is that pulling the handbrake on is definitely what causes the fuse to blow. If I go on a trip and replace the fuse at the start it survives the whole trip, until I arrived and put on the handbrake a d it pops immediately. Time to get the van on the axle stands and get underneath!!

I don't think any part of the hadbraket warmit system is under the car car
The switch to activate the lights in on the hand brake lever and nothing to do with the brakes them self's
You'd probably need to start looking under the centre console/ dash
 
My thinking was that the handbrake cable, or part of the mechanical handbrake system, may be chafing on the wiring underneath. My reasoning for this is that with the fuse having blown the handbrake warning light (and beep) still works fine, so it does not seem to be powered from that fuse. But I will check under the console/dash too. Thanks.
 
I think I found the problem, thanks to Chris. I unclipped and removed the handbrake boot and saw a small cable loom resting on the handbrake, right by the ratchet mechanism. A quick patch up and rerouted the loom and the fuse seems to be holding fine now, after 30 to 40 times of removing and reapplying the handbrake. Will monitor the problem long term.
 
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