Strange electrical issue

Okay, bear with me here this might get long winded .......

2002 GU 3.0 converted to TD42

Was driving earlier and my oil pressure gauge dropped to zero (was installed yesterday) so naturally pulled over and had a look. Checked the wiring out and noticed the negative terminal on the battery was cooking hot! Couldn't touch it! Tried to start it back up and turned over like I had a flat battery, I looked over some other wires and tried to start again and it cranked over like new and the oil pressure gauge worked..... for 300 metres.

When I got home I checked battery, was at 12.6v, fired it up and was still 12.6v nothing from the alternator (2 days old).

Next step was to clean battery terminals and connectors as they had a fair bit of corrosion. Once I done that I reconnected the battery and now when it's running the central locking constantly turns on and off by itself and with it tripping the radio out, the dash lights out, essentially everything that runs off the ignition. And the alternator still ain't charging 😞

Has anyone experienced anything remotely close to this or have a good idea of where to start looking? 😂

Thanks guys

Disconnect the oil pressure gauge completely and go for a drive. Alternator does not charge off idle. Start from the last thing added.

Why did you put a new oil pressure sensor in? A new replacement or second unit? Earth getting hot suggests dead short.

Hey mudrunner,

Disconnected the oil pressure gauge but still the same issue. I put one in as a second unit so I know what the pressure actually is.

I feel like somehow disconnecting the battery earlier has messed up the central locking somehow and it needs resetting, it has an aftermarket alarm fitted to it as well. It literally just constantly turns on and off by itself and tripe's everything else with it!

I checked the voltage at 3000 rpm'ish and it went to 12.94v so alternator is doing something I guess.

Your Alternator should be min 13.8 at idle.

Usual reason for a hot battery terminal is corrosion, unless they are both hot then it means a massive load.

If your Alternator is not delivering charge (min 13.8) and the Fuse etc are OK then either the Alt is shagged or there is a massive current drain exceeding the Alternator rating

Your aftermarket alarm will be complicating the issue with the gremlins, you need to sort the Alternator/current drain issue first.

So I checked the battery negative and one is running to the intake manifold which is ok (not ideal) and the other one was running to a random bracket, I felt like this one wouldn't be doing much so I moved it to a factory earth point on the inner front right guard and hey presto, no more dodgy central locking and 14v at idle.

I only just purchased the car the other day so going through a couple of teething issues, turns out the autosparky it was with last wasn't too crack hot 😂

Thanks for everyone's help 🤟🏽

Great result!

Nice one mate, yeah dodgy earths can do some pretty trippy things lol. .

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Welcome! Nice one.