R32 Gist, Battery Light On Continuously

[sheldonmcg14]

Hi all,

Late last year I took my R32 to Queensland raceway for a morning session, after several warm up laps I noticed the alternator/battery light was flickering on the dash.

I pitted and popped the bonnet to inspect, upon inspection I noticed that the B+ wire off the alternator was coming loose, I removed it, sanded the terminal down on the wire and refitted.

After several more laps the light came on for good and I pitted only to find the thread the B+ wire bolts onto had actually shorted out through the plastic casing in between the alternator housing causing the alternator to fry itself.

I called it quits and had the car towed home. Removed the alternator and sent it to my sparky to inspect/rebuild. They rebuilt it for me and said all was good to go.

I fitted this new alternator, tested it and then made my way to the next QR morning sesh a few weeks later. Once again the first few warm up laps went ok and then the light came back on, this time it didnt flicker and just went solid.

Immediately pitted and read a reading of 17-19v through my Power FC (Yikes), popped the bonnet and now the starter loom B+ wire had melted and gone brittle, the alternator was stinking and hot.

I called up my sparky and told him what happened, cracked the shits big time with the car and towed it home once again, not touching the POS for 7months.

My partner finally convinced me to get it working again, so I stripped the engine loom, starter loom and alternator from the car to inspect/get repaired/replaced.

The engine loom had zero signs of melting/hotspots/brittle, the starter loom had about a foot of melted B+ wiring and the alternator was funky as.

I took the alternator back to the original sparkies for them to check, they remembered my last conversation with them from when I was at the track. They replaced the unit with a brand new Bosch unit and repaired my damaged starter loom. They said they had never seen an alternator so discoloured and heat affected before.

Went home and fitted the repaired loom and new alternator they supplied, the car had been sitting around for so long that the battery was flat, we trickle charged it for the day and when we connected the battery terminal to start it up, I noticed that the Battery light was on, albeit the key not even being in the ignition and the ignition being in the off position.

Started the car and the light stayed on, Power FC read just under 13v, now I have no idea whats causing the light to stay on, I left the car and am now at a point where I want to get this fixed once and for all.

So Im here asking for advice, what the heck could be causing this? I have not taken the car for a drive yet as I want to find out what is causing the light issue before I could potentially cause more damage to this new and expensive Bosch alternator.

The car has the following

RB25det ser1 conversion

RB20det loom

RB20det power FC

Z32 AFM

6boost, td06, 50mm gate and makes a little over 400rwhp.

I have pulled the cover off the Apexi Power FC to check it wasnt damaged from overcharging which was lucky.

What else could I look at?

I am a mechanic by trade but was never too into the electrical diagnosing side of things.

Im currently away for work for 2weeks but my partner is at home and she is experienced with cars etc so she will be checking issues for me that are suggested.

Any help would be greatly appreciated, I want to get this very expensive garage ornament running smoothly again.

[89CAL]

I forget what the exact numbers are but the battery light comes on below 12.8v and above 15v from memory. This could explain why it's on.

Have you checked actual voltage at the battery/positive terminal on the alternator? The power fc isn't always 100% right.

Check that and see if it's got enough charge because 13v is too low

[LTHLRB]

alternator voltage output on most cars is 13.8 to 14.1v or thereabouts. any less than that (which it most likely is) its going to be an alternator. Any higher it will most likely be the alternator regulator.

easy as to test, get yourself a multimeter, test the back of the alternator where the power cable bolts onto.