 | Home > Maintenance & Modifications > Front electric windows - motor removal? |
 
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| Marlin.45 Member Since: 20 May 2014 Location: Llangadog, Carmarthenshire Posts: 54   
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Today I noticed that the electric pass window was not working. So first check - the power to the motor plug toggles +/-12v at the terminals when the switch is pressed up/dwn - so that seems fine. Fault appears to be the motor?
Looking at the location what's the best way to get it off to check it for seizure etc.? Unscrew the four torx heads on the underside motor or.....? That is probably what it is as the surface of the motor body has signs of corrosion. 2006 TD5 90 County 1961 MF35 |
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22nd Jan 2022 4:36pm |
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| Marlin.45 Member Since: 20 May 2014 Location: Llangadog, Carmarthenshire Posts: 54
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Now fixed!
Despite the potential being correct at the motor plug when disconnected I thought I would do a continuity check on the cables from the bulkhead to the door. The blue one had a high resistance. So just enough to allow the voltage to rise to the required level but with the resistance under load that would have dropped off to nothing! Replaced the cable and all is right with the world. Just goes to show - do a continuity check over checking the volts!  2006 TD5 90 County
1961 MF35 |
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23rd Jan 2022 3:01pm |
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| dorsetsmith Member Since: 30 Oct 2011 Location: South West Posts: 4554 |
top marks
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23rd Jan 2022 3:31pm |
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| LandRoverAnorak Member Since: 17 Jul 2011 Location: Surrey Posts: 11324 
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Yes, unfortunately a wire can still allow voltage but no amperage if it's damaged, essentially creating high resistance. It can be fine when tested but as soon as you put a load on it (the motor in this case), there's not enough current getting through to do anything useful.
You can test the motor by applying a direct 12v feed and seeing if it runs. Whilst it's possible that it's failed, it's far more likely to be a wiring fault as they're notorious for breaks in the link to the door. Darren 110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak "You came in that thing? You're braver than I thought!" - Princess Leia |
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15th Aug 2022 6:03am |
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| MattHerts Member Since: 14 Aug 2022 Location: Hertfordshire Posts: 5 |
Thanks Darren, I had read plenty of threads where everyone said the wires are known for failing in the door grommet, so thought it was the end of it when I found a rusty looking old repair. I'll replace the both the red and blue with new. I guess the connectors cant be reused if they are crimp fittings.
Now just got to figure out how to disconnect the white connector by the A frame without breaking it, cant see how they clip together. Cheers for the advice |
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15th Aug 2022 10:52am |
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| macfrank Member Since: 05 Nov 2015 Location: somewhere in the north Posts: 1081  
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Welcome  Ok, first, voltage doesn't flow Current does. In an electrical circuit voltage, current and resistance depend on each other by Ohm's law: current = voltage / resistance, or in symbols I = U / R.
Units are Volt, Ampere, Ohm. The voltage "provides a potential" for a current to flow. The resistance limits that flow. On a disconnected car battery you can measure 12V, but there is no current flowing between the terminals. Why? Because the air between them has a high resistance (12V / "very big Ohms" = 0). To get a current flowing, you could increase the voltage. Think 100 million Volts, it's called lightning 
Or you decrease resistance. One metre of a 1 mm^2 copper wire has a resistance of 0.0175 Ohm (we say 17.5 milli Ohm). If you connected such a wire directly to your battery terminals, you would get 12 / 0.0175 = 685 Ampere. Please don't. A car battery is able to provide that Amperage (for cranking), but it would instantly burn our poor, tiny 1mm^2 wire  Good experiment for a school class, though 
Home work: a) Measure the resistance of a spanner long enough to connect the terminals of a 12 V battery. b) Calculate, using Ohm's law, how big the current would be, in case anyone dropped that spanner onto the terminals. c) Write an essay on why it is a good idea to always be aware of sufficient insulation, be it battery terminal covers, gloves, wire sheathing, or distance. hope it helps Last edited by macfrank on 15th Aug 2022 3:30pm. Edited 2 times in total |
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15th Aug 2022 12:03pm |
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| MattHerts Member Since: 14 Aug 2022 Location: Hertfordshire Posts: 5 |
Thanks for the reply Macfrank. I recall some basics from GCSE physics but have almost no experience of practical application. I'd better stop bandying around technical terms like "flow" and "current" when I don't know what I'm talking about!
Have tested resistance across the wires from A frame to motor and both giving 0.2 ohm readings so unfortunately not the usual damaged wire in door opening that so many other people on here have experienced. Will check the wiring from A frame back to switch...otherwise I guess it's a new motor. Next question is how to get to the motor. As the window is stuck in the up position, I can't access the clips to detach the window regulator from the glass. If I tape the window up to stop it dropping down, can I just unbolt the inner door card to expose the regulator and motor dangling off the bottom of the window glass and detach them then? Does anyone know a simple method to lower the window so I can disconnect the regulator from the glass and slide it out the usual way? PS if a new question should be started in a new thread, please let me know and I will repost Cheers Last edited by MattHerts on 15th Aug 2022 5:03pm. Edited 1 time in total |
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15th Aug 2022 1:06pm |
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| LandRoverAnorak Member Since: 17 Jul 2011 Location: Surrey Posts: 11324
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Do test the motor with an independent supply before you commit yourself. Darren
110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak "You came in that thing? You're braver than I thought!" - Princess Leia |
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15th Aug 2022 1:29pm |
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| MattHerts Member Since: 14 Aug 2022 Location: Hertfordshire Posts: 5 |
I definately will check it Darren, just can't get to it atm as window is in the closed position so I haven't worked out how to get the inner door card off. Will try connecting a battery to the connector by the door just to see if it runs.
Think I have found a poor connection/continuity on the red wire from A frame to switch. The multimeter jumps around from a nice healthy 0.2 ish ohms to no connection and back so Im guessing cable damage behind the dash somewhere. Going to have a browse round here to see if I can find a guide to accessing and replacing that section of wiring. Cheers |
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15th Aug 2022 5:34pm |
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