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

[clankilpatrick]

I
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.

Ron, discnnected the wire from the sensor before i drove to work this morning and no change. It seems to be acting as a rev counter. Put the foot down and the needle goes up off the scale, ease back on the revs and the temp gauge returns back to normal operating temp.

Will try some of the earthing suggestions this evening.
cheers
Dave

[p38arover]

Blknight.aus has confirmed what I thought about the sensor/gauge.

I think I'd start looking at ground wires behind the dash after you've had a look at JustinC's earthing suggestions.

[clankilpatrick]

Good evening All,
many thanks for all of your input. Unfortunately I couldn't check the earthing suggestions this arvo as I got home late and the light had gone. Will have a look at lunctime tomorrow when the motor is a bit cooler. I did have a look at all of the gauges earth wires and they seem all intact. I have a car sparky mate who is going to put a dc voltage clamp on to check the alternator for me as well. I am sure the solution once found will be simple. it's just finding it that's the difficult bit.
Thanks again everyone, I will keep you updated
cheers
Dave

[clankilpatrick]

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.

Black Night,
AFAIK ??? Mate don't know what that acronym stands for. And For All I Know???? possibly. And whats a shed class rover?
Got to keep up to date with these things I guess.
cheers
Dave

[rick130]

AFAIK = As far as I know
shed class = Series and 90/110/130

[JamesH]

I never had any trouble with the warning gauges but i did with temp gauge and fuel gauge to a lesser extent.

We always thought it was earthing but the sparky tried different combinations of straps here and there and the only solution that worked was to leave them all on. So apparently I have earthing points all over the shop.

Seems good now. The rising temp gauge on hot days with aircon on is not nearly as bad - and what I know now is that it's real and a recore will be due soon.

Earth everything everywhere seems to be the go for Defenders.

[rick130]

FWIW I fixed the earthing problem with my Temp gauge by fitting a VDO mechanical one :D
Problem solved.

Our Patrol has the same issue with the fuel gauge when the spotties (Super Oscars) are turned on, and I used a genuine Nissan loom for them :rolleyes:

[clankilpatrick]

AFAIK = As far as I know
shed class = Series and 90/110/130

Aha. Thanks for the eureka moment.
cheers
Dave

[clankilpatrick]

Good evening All,
firstly many thanks for all of your help. Slowly working my way through everything and it looks like that the alternator may be at fault after all. My question to all of you with much more knowledge about these things then I is
"What is a good alternator upgrade option" If I have to fork out for a new one I would rather pay for a Bosch or similar that apparently has more grunt and has replaceable brushes and regulator. Has anyone done this upgrade before and have a part number handy? I have found a few mentions in previous posts but only for the 200 tdi not the 300 and there was no detailed info.
once again,
many thanks in advance.
cheers
Dave

[justinc]

Good evening All,
firstly many thanks for all of your help. Slowly working my way through everything and it looks like that the alternator may be at fault after all. My question to all of you with much more knowledge about these things then I is
"What is a good alternator upgrade option" If I have to fork out for a new one I would rather pay for a Bosch or similar that apparently has more grunt and has replaceable brushes and regulator. Has anyone done this upgrade before and have a part number handy? I have found a few mentions in previous posts but only for the 200 tdi not the 300 and there was no detailed info.
once again,
many thanks in advance.
cheers
Dave


Dave,
We use the 300Tdi disco 100mp alternator as a defender upgrade.
It is a straight bolt on, but may have to change pulleys if you have a pre 1996 model with the larger diameter alternator pulley, as the new ones usually have smaller ones and this makes the belt slack.(Or leave the pulley on, and fit the later belt, part number ERR5911, which is 1580mm long as opposed to 1595mm long for the early one.)
It hasn't been my experience that the brushes and regs are a problem with these Denso or Marelli alternators, plus don't forget that by the time the brushes etc are no good, you really should be looking at slip rings and bearings etc anyway...

JC