BruceM Posted October 12, 2017 Share Posted October 12, 2017 Having followed with interest this thread http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Ducato-drivers-window/47975/#M542466 about a driver side electric window staying open there was a certain irony when today having opened my A Class’s driver side electric window it failed to close. Some quick diagnostics revealed a blown 10amp fuse. My concern is that it blew at all. I’ve opened and closed the window and the door several times after the fuse change and everything is working consistently. So hence my question, do vehicle fuses eventually wear out? Currently that’s the only explanation I can come up with. If they don’t then I need to investigate some more. Link to comment Share on other sites More sharing options...
Tracker Posted October 12, 2017 Share Posted October 12, 2017 Fuses don't wear out as such but continual vibration, like door shutting or slamming, engine running, suspension bumps etc. can take their toll over time and shake the contacts enough to break the circuit. If it blows a second and third fuse only then would I investigate further, meanwhile always carry a spare fuse or two! It might pay to check for security and potential internal corrosion of any connections in the circuit. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 12, 2017 Share Posted October 12, 2017 I think the metal used in the fuse will affect how it performs over time. There have been many documented occasions were fuses have failed for no reason, and once the fuse is replaced doesn't blow again. Some fuses take next to no current and others will run hot as they may be up near their current limit. This constant heating and cooling must have some effect on the metal strip. As Tracker says some of the fuse metal strips are very thin and must be prone to weakening from vibration. But having said that, a door electric motor is prone to quite variable electrical loads as the vehicle ages and the mechanism 'drags'. Or at least it has on all the old vehicles I have owned. On my last car, I had to make a conscious effort to pause after lowering the Drivers window before sending it back up or the 'load' sensor would temporarily trip. Link to comment Share on other sites More sharing options...
BruceM Posted October 13, 2017 Author Share Posted October 13, 2017 Thanks both, your observations are useful. The one item I’ve not serviced is the electric window mechanism. When we talk about the mechanism ‘dragging’ might we be referring to a lubrication issue causing the motor to be put under a greater load and consequently drawing an increased current? Also, I’m unfamiliar with how a load sensor would operate. Is this a mechanical device that cuts the power if the window meets an obstruction or is it an electronic device monitoring power consumption which presumably would rise if the motor stalled due to an obstruction? Link to comment Share on other sites More sharing options...
Alanb Posted October 13, 2017 Share Posted October 13, 2017 As Allan has speculated above the answer can be yes. My first MH dated from 1990 and was fitted with "Continental" torpedo shaped fuses. I did find one fuse which must have been operating close to its rating. These fuses have an element which runs along one side of the ceramic? body. This element had lengthened over time so that it arched away from the body. This lengthening could only result in a reduction of the csa, and hence the current carrying capacity of the fuse. Failure would be progressive. I have no experience of such failure on more modern blade style fuses. My experience was many years ago, and I do not wish to cause alarm. Subseqent to my discovery I read a letter in MMM which reported a fuse holder cover giving off smoke when the vehicle was ascending Norwegian passes. In this instance it was the fuses supplying the engine cooling fans that had failed. I conjectured that if the fuses had been fitted with the element visible under the cover, it was possible for the deformed and hot element to touch the plastic cover. Alan Link to comment Share on other sites More sharing options...
keninpalamos Posted October 13, 2017 Share Posted October 13, 2017 I can remember the torpedo type fuse, Awful design. Quite often the caps that fitted over each end of the the ceramic holder could wear with heat and vibration and they could be fiddly to fit correctly. Oh for the days of the glass tube fuse. ;-) Link to comment Share on other sites More sharing options...
Alanb Posted October 13, 2017 Share Posted October 13, 2017 BruceM - 2017-10-13 9:31 AM Also, I’m unfamiliar with how a load sensor would operate. Is this a mechanical device that cuts the power if the window meets an obstruction or is it an electronic device monitoring power consumption which presumably would rise if the motor stalled due to an obstruction? I have some diagrams for X244 Ducato. The window controls route via an electronic control unit "ABI or M135" on the diagram. I believe that it is this unit that contains the electronic load sensor. This sensor normally functions if the closing window jams against a trapped object, or when the window reaches the end of its travel on auto operation, i.e. when you hold your finger on the button for a longer time. My apologies to Allan for pre-empting his reply. Alan Link to comment Share on other sites More sharing options...
tonyishuk Posted October 14, 2017 Share Posted October 14, 2017 I seem to recall that DC fuses could fail over time as the electron flow was in one direction and took with it, electrons from the metal and thinned the fuse wire, Could be old mechanics tale ! Rgds Link to comment Share on other sites More sharing options...
Tracker Posted October 14, 2017 Share Posted October 14, 2017 tonyishuk - 2017-10-14 3:49 PM I seem to recall that DC fuses could fail over time as the electron flow was in one direction and took with it, electrons from the metal and thinned the fuse wire, I've just had all the plumbing taken out of the house and turned and refitted to make the water flow the other way to even out the wear in the pipes. Our plumber said it was a good idea to do this every 50 years or so rather than allow the water to wear a hole in the copper tube from always flowing one way! Link to comment Share on other sites More sharing options...
Geeco Posted October 14, 2017 Share Posted October 14, 2017 Rich, you are probably correct in reversing your pipes. As you no doubt realise south of the equator water drains in the opposite direction ( clockwise from memory) to the northern hemisphere. This I suspect is why most plumbers here like to fit kitchen sinks made for the northern hemisphere to even out the wear! Link to comment Share on other sites More sharing options...
aandncaravan Posted October 15, 2017 Share Posted October 15, 2017 Bruce, yes the mechanical effort on the Motor seems to increase with age. I think more so because of 'Drag' on the runners rather than the Arm/cable mechanism. Spraying Silicon spray down the Glass sliding Channels seems to help on my old vehicles. Link to comment Share on other sites More sharing options...
kevin hawkins Posted October 15, 2017 Share Posted October 15, 2017 Fuses get tired with age and blow due to electric current flowing through them, this was explained thoroughly when I was a apprentice electrician 50years ago. If it doesn't blow when another fuse is fitted it's ok. I won't bore with the details but on 3phase systems when one fuse blew we always replaced the 3 because you could bet one of the other would blow within a week, (^) Link to comment Share on other sites More sharing options...
Tall_Mike Posted October 16, 2017 Share Posted October 16, 2017 Think they do, - Either by vibration, most vehicle fuses get a good shaking, or by constantly heating and cooling, - not to the extent that they trip but under loads they heat and cool. - Our pack of spare fuses cost about £3.50 and I suspect they are made of cheese. When one fuse blows, odd things happen and current may flow in unexpected ways, - Also the fuses here most probably put in together, so they age together, - bit like light bulbs, - once one blows, you can be sure more will follow, - my theory anyway. Saying that in my car, in probably 30 years of motoring, only a couple of fuses have ever blown, and they have been my fault, - doing something I shouldn't have with the battery still connected 8-) On a system that's working as it should be - it's a very rare occurrence. Link to comment Share on other sites More sharing options...
BruceM Posted October 21, 2017 Author Share Posted October 21, 2017 The fuse blew again, same symptoms as before. So I rigged up my trusty watt meter to measure the current flow whilst the window is operated. I did this by pulling the 10 amp fuse and making the watt meter source ‘+’ the fuse holder 12v in, the watt meter load ‘+’ the fuse 12v out and commoned the source and load ‘-‘ to the chassis. The wattmeter started up fine, showed the battery voltage, but when operating the window it did not show any current drain. So I’m at a bit of a loss to understand what 's going on. The fuse incidentally also seems to protect the rear view camera display. I’m beginning to wonder if the fuse might actually be providing power to some switching relays hence the undetectable current drain? Link to comment Share on other sites More sharing options...
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