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Old 03 January 2011, 10:09   #1
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200 Optimax Wires melted??

Went down to the boat this morning hoping to go for a cruise. Had not been started in about 6 weeks and with all the cold weather knew the batteries would be worse for wear. Sure enough they were only reading about 11v and not enough to turn the engine over, I took the battery from the Discovery and swapped it with the starter battery. Tried turning it over (maybe for a 30 secs or so) then I saw smoke coming from the cowling?? Disconnected it immediately and lifted the hood. The insulation on the cables around the alternator were melted and the air filter was almost on fire?? Also noticed the positive on the solenoid was melted.
Hopefully just a few wires to replace but im baffled as to how it happened?? Battery was 12v and wired in correctly (+ and -) checked this a few times afterwards to make sure I hadnt crossed the battery cables?? and the Aux battery was disconnected.
Didnt think the rating was much higher than the normal starter battery.
Anyone any ideas??
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Old 03 January 2011, 10:13   #2
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The motor would only take what current it needed.
By all means rewire it but find out what caused it before you try starting it again.
11v on a 12v battery is knackered.
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Old 03 January 2011, 10:20   #3
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I could well be wrong but I think I once read that starter motors and maybe alternators can create a short circuit when they are seized.

11v should've turned the motor over, my opti will although it won't power the ecu at the same time. If you put power to the starter and it can't spin then that can be a short (I think) and maybe same applies to the alternator.

Just a thought
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Old 03 January 2011, 10:50   #4
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Batteries themselves won't cause any problems with melted wires providing they are the same voltage and you simply swapped the two over. If you connected the negative to positive and visa versa then I would expect there to be built in protection to the outboard to protect it's self. So that just leaves the starter motor and alternator.

You said you tried to turn it over for 30 seconds. Was the starter not cranking the engine?

If this was indeed the case then it could be either a case of seized engine or faulty starter, both conditions that could draw more current from the battery (starter motor under heavy load or shorted) and so heat up the "weak link" in the wiring and melt it. There are not normally in line fuses on such power cables.
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Old 03 January 2011, 11:05   #5
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There's a fused link between the alternator and the slave solenoid which would pretty much eliminate an alternator issue, another finger pointing at your starter.
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Old 03 January 2011, 11:18   #6
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Thanks for replies guys, always great to get others thoughts.
Engine was turning over but it was like it wasnt drawing enough power to start, Voltage on the smartcraft gauge said it was 11.5v although the battery had come from the landrover and was definitely well above that. Starter motor was spinning fine just not enough to turn engine over (engine not seized). Never had a prob with the alternator before and was working just fine up to 6 weeks ago on my last trip, temp dropped down to about -16 C and rarely came above freezing during past few weeks so that would explain batteries but surely this wouldnt affect the wiring???
Still baffled??
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Old 03 January 2011, 11:37   #7
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Quote:
Originally Posted by Waterman View Post
.... Starter motor was spinning fine just not enough to turn engine over (engine not seized).
Erm... something odd, this is not how the starter motor functions. If it's spinning but not engaging the engine there's a starter motor/solenoid issue. If it's engaging the engine and the engine isn't turning but you continue to hold the ignition start on, then it's not surprising you have melted the cable. A static starter motor will draw hundreds of amps with consequent heating. While cranking even a proper starting engine, the battery volts will drop close to 9v.
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Old 03 January 2011, 11:38   #8
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I thought some landrovers had 24v batteries. Or are these all on pre 1960 models?
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Old 03 January 2011, 11:42   #9
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Quote:
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I thought some landrovers had 24v batteries. Or are these all on pre 1960 models?
They were usually ex MOD FFR (fitted for radio). Not sure if they used 24v batteries or two 12v?

Even pre 1960 ones were 12v.
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Old 03 January 2011, 12:02   #10
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Erm... something odd, this is not how the starter motor functions. If it's spinning but not engaging the engine there's a starter motor/solenoid issue. If it's engaging the engine and the engine isn't turning but you continue to hold the ignition start on, then it's not surprising you have melted the cable. A static starter motor will draw hundreds of amps with consequent heating. While cranking even a proper starting engine, the battery volts will drop close to 9v.
Sorry, my mistake I should have said it was engaging and slowly turning the engine over, just not enough to start it. Looks like I may have caused it myself by keeping it turning over for too long, although I have definitely turned it over for longer before without this happening.
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