Very annoying electrical problem

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Co-Pang-Yang

Co-Pang-Yang

Well-Known Member
Posts
2,930
Location
Colchester, Essex
Hi, my Disco's electric problem is really starting to get on my wick lol, so i'd thought i'd turn to the forum for help.
Been having an intermitant problem with batteries not charging and loosing power.
After findingthat the cover on the back of the alternator was arcing on the terminals, removed that and it was fine for a bit.
However after a couple of hours the battery was being drained again. Headlights dim, heater fans slow and something else that i hadn't noticed before.
Heard a clicking noise coming from behind the dash, it would speed up for a couple of seconds and then full power was restored for about 5 minutes then start to drain again to the point where i lost everything including the rev counter, then power fully on again. Also on one occation (that i noticed anyway) the immobilzer light was flashing slowly, about once every 5 seconds or so.
Was wondering if a fault with my immobilser could be stopping the alternator from charging the battery?
Please help i'm very confused lol.

Cheers Chris.
 
What Disco do you have?

Sounds to me like your alternator is screwed....or your battery is on it's way out. I've had it before where the battery has a faulty cell and works fine sometimes but other times causes intermittent issues. Winter normally brings these battery or alternator issues out...
 
Sorry, its a 300tdi manual. Yer it is a possiblity, we've charged and tried 4 different batteries on it and they've worked for a bit then died. The alternator is off a 200tdi doner car i've got, we changed the pulley over and re-wired it to fit the 300's loom and it seemed fine, defently worked on the 200tdi.
Is there anyway of testing a alternator? Really don't want to fork out over £100 on a new one until i know this one is at fault.
 
Co-Pang-Yang said:
Sorry, its a 300tdi manual. Yer it is a possiblity, we've charged and tried 4 different batteries on it and they've worked for a bit then died. The alternator is off a 200tdi doner car i've got, we changed the pulley over and re-wired it to fit the 300's loom and it seemed fine, defently worked on the 200tdi.
Is there anyway of testing a alternator? Really don't want to fork out over £100 on a new one until i know this one is at fault.
Click to expand...

Might be a possibility that the earth circuit for the alternator back to the battery -ve terminal is faulty.
Does the car start easily?
Have you ever checked the two earth strap connections to the chassis?
They form the earth path, bad connections - poor charging.
Also have you checked the +ve cable connection to the alternator is tight?
 
Haven't closely looked at the earth straps tbh, i will do that in a bit when i venture out in the snow to the workshop.
When it has power it only takes a couple of turns of the starter to fire, however when i dies you have to jump it off another car and have the cars connect for a couple of minutes before there enough power to get the turning over.
All the alternator cables are tight but i will check them again tonight.

Not sure if its related but a couple of weeks ago the starter motor wouldn't engage off the key, just heard relays clicking but nothing else. As a temperary fix i have a loose wire connected to the + on the starter that i touch to the + of the battery to start it. Dunno if the loss of ignition connection has anything to do with it or not.
 
unfortunately that doesnt test an Alternator - you need to be able to test it under load and check for Ripple current. Look in the Q's and A's bit - or take it to Halfrauds or similar, who can test it for nought.
 
when i was at a garage i mentioned battery problems and they came out with a device that tested my battery and alternator for me for free, just ask em.
 
Halfords tested it and it came back as 13.6v, the young spotty Halfords lad reckoned it was the alternator, but i'm still not 100%.
Can the spider unit have any effect on the charging?
Its been fine the last couple of days then tonight it stopped charging, got really low and caused the doors to lock with the keys in it and engine running. After about 10 minutes the power came back and it unlocked itself.
Thats really confused me.
 
what did he test it with? A multimeter?

he should have used a Bosch BAT121 tester which tests the battery on load/no load - He can also test the alternator with the same kit.

Take it back and complain.
 
Last edited:
get him to test the battery and show you the readings (yu can get a printout). When testing the battery it is done at no load and engine off.
The alternator test is done with the engine on and then with the lights on to load the system, so two tests.
make a note (or get a printout) for the batt and alt tests and let us know what they are.
 
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