 | Home > Td5 > Defender td5 110 y2k. Brake light fuse blowing |
 
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| munch90 Member Since: 26 Oct 2013 Location: guildford Posts: 3558  
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I would say its nothing to do with alternator itself
if fuse goes when pedal pressed then say its got to be a short somewhere has it got high level brake light if so check wiring to that was it blowing the fuse before other work done ? |
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24th Mar 2014 9:37pm |
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| deaftonewonder Member Since: 20 Sep 2012 Location: plymouth Posts: 3  
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Hi thanks for the quick reply!
Thats what i thought & i spent sat & sunday tracing all the wires in the rear loom and all look fine, no chafes and perfect continuity. As i say, when its at idle on the driveway the brake switch operates fine but under load driving down the road it will blow when the brake switch is pressed -thats why i thought is it when the alternator kicks in to charge the battery? it is only since the rectifier & brushes have been changed My wagon is pretty famous for spurious electrical gremlins & really kicking myself for buying a td5 now... |
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24th Mar 2014 10:04pm |
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| munch90 Member Since: 26 Oct 2013 Location: guildford Posts: 3558
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what's the voltage when charging?
perfect continuity but is there any leak to earth? if alternator was overcharging bulbs would blow not fuse |
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24th Mar 2014 10:12pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20612
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Sounds like a possibly damaged live feed wire, test for continuity between live and earth with the battery disconnected but the brake pressed. If you get any reading there is a short, possibly might not show if it's intermediate.
You must disconnect the battery though. 
Regardless of the above the next route is wire tracing which is the next stage but can be difficult. Look for any signs of damage of wiring and wires visible at the very least. Are your front sidelights affected at all? Also disconnect the lights then operate the brake and see what happens. If it still blows then it's a short if it doesn't then it could possibly the the light fixture" Also check the connectors. Chillin In The Backwoodsπ¬π§πΊπΈ β½οΈπ’οΈβοΈπ§°πͺ |
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24th Mar 2014 10:24pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20612
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It might also be that a short is caused on the road simply because it's an intermittent short caused by the slight movement from being in movement.
The extra alternator voltage also makes the voltage a touch higher also so is even more likely to blow the fuse even faster. The extra voltage also means the short will jump just that little bit further through possibly damaged insulation. Chillin In The Backwoodsπ¬π§πΊπΈ β½οΈπ’οΈβοΈπ§°πͺ |
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24th Mar 2014 10:27pm |
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| deaftonewonder Member Since: 20 Sep 2012 Location: plymouth Posts: 3
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Hi guys
Bit of an update: Been going through fuses like crazy getting to & from work this week but they're free so 
Downloaded a copy of rave & printed out circuit diagrams / headers of interest so will be an interesting weekend.... tore my dash apart thisafternoon and couldnt find any chaffes in the loom. I Borrowed a fluke from work & tested a few wires but lost the light so will investigate more tomorrow One interesting thing though: i tested the voltage across fuse 6 with the engine running (i know its not great for the multimeter but its free) When i pushed the brake pedal i got 17+ volts! -any thoughts? Thanks for the above replies, i'll be working through the suggestions tomorrow! Edit: Forgot to say, sidelights are ok and no other systems effected (touch wood!) Doesn't even blow when in reverse, just when the brake is pedal touched (intermittently) |
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28th Mar 2014 8:54pm |
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