Defender 300 TDi electrickery

[clankilpatrick]

Afternoon All,
I hope someone may have encountered this problem and can set me on the path to fixing it.
The other morning I turned into work rarther sharply and the oil pressure light and alternator light came on. Not too much of a problem I thought maybe just a little low on oil that sloshed up to one side of the sump going around the corner. (The alternator light had been coming on occasionally when I lifted the foot off the accelerator and just coasted when going into town). I left it for the day and when I went to go home both lights were still staying on AND the temperature gauge was way off the scale even when the engine was cold. As I have a littleblackbox hooked up as an engine watchdog it was going off every 5 seconds. Bloody annoying. So what have I done to try and fix this?
1. Charged the battery fully
2. topped up with oil
3. pulled the dash out and checked all the connections on the gauges to the Little black box.
4. Followed the temperature gauge sender wire from the thermosat back as far as I could to check for any insulation missing or shorts.
5. checked the expansion tank for correct coolant levels to make sure LBB float was covered.

I haven't taken it for a run yet but I did start it and it looks like the oil pressure light and battery light are no longer on BUT the bloody temperature gauge is so far over to the right its nearly off the scale. The odd thing is when I rev the vehicle it moves back over to the left briefly. i also failed to mention that when I took it into town yesterday before pulling it apart, the gauge did spend some of the time where it should be sitting, but did jump up off the scale most of the time and refused to stay in one spot.
So I have disconnected the LBB for the mean time so I can drive without the buzzer screaming at me and am hoping that someone out there can point me in the right direction.
Many thanks in advance.
cheers
Dave

[dullbird]

is there a regulator at the back of the dash to all the guages?

[lardy]

maybe your alternator is packing up and it just so happens that the temperature sender unit is dying wierd'er things have happened any relays to go on that not sure haven't looked

[clankilpatrick]

Regulator?? Mate there may be but I honestly couldn't say. What does it look like/where is it situated? its a Dec 96 TDi 130 if thats any help at all.

[clankilpatrick]

Thats a possibility I guess. I will have a look at what the alternator is doing tomorrow. I hope the sender hasn't packed it in as it will be a bugger of a job to replace.

[Chucaro]

What is voltage reading ? 13.9 volts with the lights off?

[p38arover]

is there a regulator at the back of the dash to all the guages?

I can't see one in the Defender wiring diagram (they were used on older cars with Smiths instruments). The instrument power feed is via a white wire from the ignition switch through fuse F1 then to the WG wire to the instruments.

The ignition feed comes from the alternator NY wire through a diode, then a YN (not NY) wire to a 24 ohm resistor then, as a white wire, to the ignition switch. The one side of ignition light is fed off the YN wire, the other end off the WG wire feeding the instruments.

If those NY or YN leads were dicky, it might affect all instruments and the ignition light.

What happens to the temp gauge when you unplug the lead at the sender?

I think (not sure) that the gauge might read high if the sensor wire is grounded.

[clankilpatrick]

Gidday Ron,
Mate thankyou for the input. I will have a go at disconnecting the sensor tomorrow and get back to you tomorrow evening.
cheers
Dave

[Blknight.aus]

most temp sensors go high on a short circut and low on open.

and AFAIK all the shed class rovers and the D1's do the same thing.

[justinc]

Sounds like Poor eathing, from battery to chassis, and battery to body. Hook up a jumper lead from neg battery terminal to seat box or a good bulkhead earth and see what happens then. There are also 2 earth wires from the RH side of the transfer case to the main wiring loom to the rear of the vehicle, in addition to the main battery earth that comes out of the seat box, straight to the chassis where the crossmember bolts on and to the transfer case LHside. ALL these can give trouble like that if any are loose or corroded.

JC