Hi all I hope someone can throw some light on this for me. I recently bought a P38 4.6 1996 automatic & it broke down on the way home. Rev counter & speedo fluctuations & engine holding back, the car wouldn't restart after turning off so I fitted a new battery & car drove home fine. The car wasn't charging & fuse box smelt hot and initially had no battery light until I fitted the new battery. I replaced the alternator and the car is now charging but goes flat over night. I checked for current drain 0.05amp. Charging battery relays 18 & 19 got hot. The result from the electric sticky tests are
Engine off full load 30sec 11.31v, voltage across battery at ldle no load 13.87, voltage across battery 2000 rpm no load 13.86,voltage across battery 2000 rpm full load 13.37, voltage at alternator 2000 rpm 14.31, voltage drop ody & battery neg 0.18, voltage drop alt pos & battery pos 0.8, voltage drop battery neg & 1st ground 0.06, 1st ground & block 0.10, alt housing & block 0.00, alt pos & alt housing 12v? Surely that can't be right? I'm confusing myself now.
Is alternator faulty & what could have caused my initial problems? Also srs light is on but I suspect that's a separate issue but just in case thought I'd mention it. Oh and there is battery voltage on the brown & yellow wire to the alternator, is this from the becm? If I connect a bulb from the terminal on alternator this goes to and poss terminal of battery the bulb illuminated until engine started then goes out, once turned of it comes on again.
Sorry if this reads rushed but I spent ages typing it out just now & the system timed out & I lost everything & had to start again.
Mark ( newbie)
Hi Mark, glad you found your way here. Something is odd here and as I mentioned on the other forum (no, lads, not that other forum, but another one), hot fuse box and relays being held in when they shouldn't could suggest someone has replaced the fuse box with the wrong one. Fuseboxes, particularly the early ones, did have a habit of burning out. They can be rebuilt is you are handy with a soldering iron (see http://www.rangerovers.net/repairdetails/electrical/fusebox.html) but if you've got the wrong one all bets are off.
The voltage drop between battery and alternator suggest that there's a dodgy connection. Maybe where the two cables are joined at the starter or just corrosion inside the terminals. Do they look good or are they a bit on the green side?
Battery Goes flat over night............what's the voltage on the battery in the morning?
Need to be finding what's pinching all of the current.
Is your suspension moving at all overnight? if so or not sure, pull the suspension delay timer relay out and temporarily replace it with a standard relay. Delay timer relay is under passenger seat. Take plastic surround off. It's the tall relay. Cant miss it. If your battery stops draining, you've found the problem.
I had battery drain on mine when I got it and an EAS leak was the cause. Delay timer was waking the BECM up all the time. My battery was also caput though as the previous owner had just kept charging it and knackered it. You have just fitted a new battery so the health of it should be good. Worth a look at that delay timer though.
Post the part number from the fuse box and someone will confirm if it's the correct one for your car.
Another good one for battery drains is rogue RF signals waking the BECM up. Everytime the car sees one, it gets ready to unlock the car as it thinks your coming. RF receiver is in the boot on the drivers side under the parcel shelf support trim.
Not sure if your year p38 is the one that people put a direct wire from the battery to the alternator. Gilbert will know.
The 96 is likely to have the long cable run from battery to alternator via starter motor, so if it hasn't been done already put a new additional cable (pref around a 25mm2) direct between battery +ve terminal and large alternator +ve. You don't have to remove the original section between starter motor and alternator, but it's one less bit of old cable hanging around if you do.
Correct fuse box for yours is this one:
http://www.island-4x4.co.uk/fuse-petrol-9497-genuine-amr6405-amr3375-p-4134.html
Gilbertd wrote:
Hi Mark, glad you found your way here. Something is odd here and as I mentioned on the other forum (no, lads, not that other forum, but another one), hot fuse box and relays being held in when they shouldn't could suggest someone has replaced the fuse box with the wrong one. Fuseboxes, particularly the early ones, did have a habit of burning out. They can be rebuilt is you are handy with a soldering iron (see http://www.rangerovers.net/repairdetails/electrical/fusebox.html) but if you've got the wrong one all bets are off.
The voltage drop between battery and alternator suggest that there's a dodgy connection. Maybe where the two cables are joined at the starter or just corrosion inside the terminals. Do they look good or are they a bit on the green side?
Hi all & thanks for your input (Gilbertd from the other forum too!) it is much appreciated and gives me plenty to work with for now. I will check them out over the next day or two as I'm working today & tomorrow.
Interesting to hear about the suspension relay too as the previous owner said he had disconnected it all but eas light comes on initially & the air bags are still fitted but the system has the manual valves in line. This was something I planned to sort out further down the line. I will check out & come back to you all.
Mark
Suspension delay timer won't stop lights coming on or suspension working. Its only function is to self level the car after you've got out and periodically wake the becm to make sure it's still level. A bizarre feature in my view. I personally am not that anal to want my car perfectly level everytime I look at it out the window. Clearly the designers thought this needed to be a must have feature and a selling point. Lol.
Not sure why the feature is there but it is unlikely to flatten the battery overnight by waking up for 2 minutes every 6 hours. It does give you early warning of a leak although I suspect that isn't why it's there. Mark's main problem seems to be that he's got relays 18 and 19 permanently energised, even with the ignition off, and that isn't good. That is almost certainly why the battery is going flat, one of them powers the engine ECU. That's why I suspect the fusebox has been changed for the wrong one. It's a '96 car so the fusebox was originally an AMR3375 which was superseded by the AMR6405 which is presumably an updated version that would be more reliable than the original. £105 from Island 4x4, so not the end of the world.
I recently reinstated the air suspension on a car a mate bought which had also had 4 Schrader valves fitted under the bonnet to allow each corner to be inflated individually. He found that without the automatic lowering at speed, it felt decidedly unstable at anything over 60 mph. He got an O ring kit for the valve block and a rebuild kit for the compressor, did those then I fitted them and checked it over. There was a couple of leaks where the air lines had been mucked about with when the valves were fitted but some decent quality joiners and a couple of feet of air line and it now works perfectly. Total cost for the lot? About £60.
First off, as Gilbertd says - check the fuse box is the correct one for your vehicle..
Second, as Orangebean says - see if there's a cable from the alternator direct to the battery, if not, then I'd look at adding one. It provides a more direct charging route, rather than going via the starter motor - which ends up being about another 2m of cable for it to go through before getting to the battery - which can cause issues especially if the starter connection gets grimy and horrible! And also can corrode internally.
The voltage drop on both the positive and negative battery cables is fairly high - you should be seeing a MAXIMUM of about 100mv drop, with a good system (with new cables etc) it can be down to like 30mV. The higher the voltage drop along the cables then the less charging current that will get from the alternator to the battery.
Having good clean battery cables, and shortest runs possible will give the best possible charge at the battery - with the least voltage drop.
If there's a battery drain issue there as well, then that won't be helping matters either - just means you're on a downward spiral to a flat battery!
Thank you all for the input so far. I thought I'd give you an update of the current status. I have removed and cleaned all the earth cables and checked the fuse box as suggested which appears to have the early original part number on it. As the alternator was still getting warm I decided to refit the old one and see what happened. The battery light has worked every time since I refitted it & the fuse box relays are behaving themselves too. The car is charging at 13.97 volts at the battery and 14.4 volts at the alternator. I will replace the positive lead as also suggested over the nex couple of days and see where we go from here. It looks as if the after market alternator is not compatible ( I know it's been said numerous times before but due to the price differences I hoped it would be ok). I have a volt meter wired to the cigar lighter for now to monitor the alternator for a day or two. I'm just a little dubious at the moment to know if it's a glitch or whether it will behave itself.
the old saying is "buy cheap, buy twice". Big alternator on p38's. I was lucky enough that the previous owner of mine treated the car to a brand new bosch one about 3 weeks before he sold it.
Seems you may have fixed your problem by simply cleaning the earths. Can't see how the original alternator would have fixed itself.
You checked the voltage drop since?
Fingers crossed you're sorted.
Hi yes the voltage drop is 0.04 v but the bonnet was open then
I would suspect the dodgy earth was showing a lower voltage than expected (if the test done was to measure the voltage across the battery it would suggest a faulty alternator) so it hasn't fixed itself, there was nothing wrong with it in the first place. If the new one you got had a short circuit rectifier, it would cause the battery to go flat and would also back feed the ignition switched circuit (via the sense wire) and cause the two relays that should be ignition switched to be permanently energised.
"Seems you may have fixed your problem by simply cleaning the earths. Can't see how the original alternator would have fixed itself".
That was my way of saying I don't think there was anything wrong with it.
Gilbertd
I think you are probably right & it just shows how easily it is to be led up the wrong path. Maybe I was looking for a bigger problem than first thought too but having worked in the trade for 32 years it was rare to find an earth fault cure a problem but of course as I previously mentioned I hadn't had much experience with the P38.
I have to say though I do love the car & hopefully we can start using it with confidence now. It's good to have support from fellow owners too and this particular forum has been fantastic with the responses.
Problem with electrical faults is there is nothing you can see going up and down or round and round. I've worked with electrics and electronics all my working life and sometimes you get faults that seem to defy logic until you find what the actual problem is and can then work out why it showed the symptoms it did. Most people would just stick a meter across a battery, look at the voltage and, if it is low, immediately blame the alternator. It's only when you check between ground and the alternator itself you see the true picture.
Just a quick update to say it's running well now so time to enjoy. Thanks all for your help
Mark
So all you have to do now is meet up with OB somewhere and get the SRS light turned off.
Where are you from Mark-H?