View Full Version : Tech (auto) problem solving

26th Aug 2011, 20:39
OK, light Friday evening entertainment. Here in the UK, a retired friend has a non-pc but very well cared for Range Rover 4.6 HSE. However, it developed a fault in that it would regularly discharge its (new) battery after 2 nights in his garage. Trips to auto electicians/workshops failed to reveal anything, meters, alternators, etc nothing discharging.
So what was it? and I have a bonus question for the correct solution.
(No giigling!) but I reckon JB folk are a breed apart

26th Aug 2011, 20:56
Plucked nostril hair shorting out the fag lighter?

26th Aug 2011, 20:59
Glove box light switch failure ?

Spunky Monkey
26th Aug 2011, 21:02
My Father's BMW has a similar problem. Caused by the alarm and some of the background electronics.
It is a problem made worse by the poor battery.
It was only 12 months old.

Battery replaced and problem not quite solved but in a liveable equilibrium.

Check that the battery is good and that it is being properly charged in the first place. As all the electtrickery bit will drain the battery.

flying lid
26th Aug 2011, 21:02
Battery Drain on a Range Rover 4.0/4.6 (http://www.rangerovers.net/repairdetails/electrical/batdrain.html)

Range Rover P38/4.0/4.6 Common Problems and Fixes (http://www.rangerovers.net/newrremedies.htm)

Battery drain on my P38 Range Rover 4.6 HSE auto - Land Rover Zone (http://www.landyzone.co.uk/lz/f10/battery-drain-my-p38-range-rover-4-6-hse-auto-27875.html)

overnight battery drain (http://forum.landrovernet.com/showthread.php/81344-overnight-battery-drain)

Hope these help


26th Aug 2011, 21:04
Not leaving the gear shift in 'Park'?

Takan Inchovit
26th Aug 2011, 21:05
Battery internally shorting - replace the new battery


replace car with suitable Japanese manufactured unit.

26th Aug 2011, 21:05
OK, quick thread, and I guess Mr Lid has been researching.
Electronic smog is indeed the answer, his newly installed weather station was sending 1 minute humidity readings over air, they in turn were trying to activate his central locking ..:D

For a real prize, what specific item caused my Ferrari owning friend's alarm to activate around three times a year?

26th Aug 2011, 21:21
A riced-up Impreza driving past? :p

27th Aug 2011, 15:28
For a real prize, what specific item caused my Ferrari owning friend's alarm to activate around three times a year?

Squeaky bedsprings when making love to his wife (as opposed to his girlfriend ?)

Lon More
27th Aug 2011, 16:21
Hope they've solved it before I pick up my new Evoque

27th Aug 2011, 16:29
The Memsahib's VW Polo had the same problem.
We'd got a new battery from Halfords due to previous
one leaking.
The NEW battery also leaked!!!!
Took it back and got another one. That's been fine, up to now!!!

Thorough wash carried out under the bonnet!!!!

27th Aug 2011, 18:39
Greasing the (metal) battery compartment or putting in a plastic liner isn't a bad idea for those who still have car batteries filled with liquid.

27th Aug 2011, 18:50
If the receiver for the central locking wasn't such a crap one (but they ALL are!) the central locking would probably not have noticed. So that the system can be as cheap as muck, the receivers are around 700kHz wide and the transmitters are somewhere in that bandwidth. This actually led to German car manufacturers attempting to get all other Short Range Devices (SRD) banned from the 433 MHz frequency range. They did get somewhat short shrift on that at the CEPT (European Conference of Posts and Telecommunications) committee.

Some 20 years back, I worked in the group that made a load of the integrated circuits for them. The car manufacturers just refused to pay for anything but the minimum performance - they were even upset when the use of superegeneritive receivers (which radiate interference like the clappers) were banned.

Might be some fun round Weymouth during the Olympics - there will be some transmissions on the frequency during the sailboat racing.

27th Aug 2011, 19:22
On my beemer it was the "final stage resistor". A french made part (Valeo) that caused massive amounts of trouble. It was a simple part to swap out. Check that the ventilation fans aren't constantly blowing - a simple bit of toilet tissue "blowing in the wind" over the air vents, after everything is switched off will tell you quickly if it's the rouge part.

27th Aug 2011, 21:11
On my beemer it was the "final stage resistor".

Exactly the same thing on my mate's BMW. It was slightly more subtle because it did its thing intermittently after he'd checked everything was off and locked the car up. Only discovered what was happening after he'd linked up a recorder overnight to monitor the voltage/current draw.

On my wife's Clio the overnight battery drain was traced to a worn through ignition circuit wire intermittently shorting out against a metal brake pipe. bit of tape and some cable ties sorted that one out!

27th Aug 2011, 21:24
a simple bit of toilet tissue "blowing in the wind" over the air vents, after everything is switched off will tell you quickly if it's the rouge part.

Only if you use pink toilet paper :ok:

28th Aug 2011, 11:25
I didn't mention that the unlocking/locking radio receiver shouldn't draw any more than 5 milliamps. That means (if it hasn't any current saving circuitry built in) it should take 8 days and 16 hours to deplete the battery by 1 amp-hour.

28th Aug 2011, 14:43
Turning off the RKE (Remote Keyless Entry) receiver isn't usually easily possible. Bit self defeating, too.

28th Aug 2011, 15:41
Has anyone suggested boot light?

28th Aug 2011, 18:29
Let's assume a 40 AH battery. If it runs down overnight, in say 10 hours, we're looking at a continuous drain of around 4 amps. That's 48 watts, so there's some appreciable power drain going on. Or the battery isn't getting a full charge in the first place. Now you can have a bigger or smaller battery, but unless it's a lot different, you aren't going to change the current into something insignificant.

I'd try measuring the current when everything is off, and also checking the battery volts under load after a run to see how well it has charged.

good spark
28th Aug 2011, 20:44
go to maplins ( the electronics pepes ) and buy for around 9 quid a blade fuse plug in digi meter, with all lecky stuff switched off replace each fuse in the fuse box with this jobby and watch the screen, when it shows current your cookin w gas simplex

29th Aug 2011, 00:39
Some years ago the remotely controlled door on our garage stopped working. A change of batteries in each remote, a check of the matching of (dip?) codes between remote & receiver, even a check of normal mains voltage at door motor did nothing to cure the problem. It turned out that a front door bell button, wirelessly operated, had been stuck in and caused interference with the garage receiver/sensor until it's own batteries died allowing the garage receiver to work normally again.

In another garage my car, with security alarm installed but not armed, routinely parked beside the ducted vacuum cleaner would discharge it's battery overnight giving me an unpleasant surprise next morning. Swapping sides in the garage cured the problem and, strangely, caused no inconvenience to the other similarly equipped car.

Despite bandwidths being allocated for various uses, or more correctly various uses being separated by bandwidths, there is significant crossover in the real world and much of it not understood.

Loose rivets
29th Aug 2011, 11:19
A quick question please.

Honda Accord I worked on tirelessly some weeks ago is displaying the ABS warning light. Honda say the brakes will work, but with no ABS.

I changed the fluid wile doing the brakes but I don't know if it goes through the ABS system. That seems to have a separate filler which was up to the mark.

I'm 100 miles from the car, but when I handed it over, the area around the wheel detectors seemed fairly clean.

Any known items that causes this fault that are common on this or any other car come to that?

The logistics are a pain.

Oh, BTW, this is the very same ABS system that saved a toddler from certain injury or worse. Seeing the child so near made my right leg nearly bend the pedal. Nothing would have made it release. The system sang out its merry howl, and worked beautifully. The lad that crashed into the back of me didn't have ANS.:(

Most anxious to get it right.

29th Aug 2011, 13:55

In Europe, RKE systems, together with tyre pressure monitors, are mainly in the band 433.05 to 434.790 MHz. So are a whole load of other generic SRD (Short Range Devices). Under the EU 'Short Range Device Decision', SRD on any frequency (there are a lot of frequencies for them) must not cause interference and must accept any interference. Many of the receivers in cars are about 700 to 900kHz wide to allow the use of SAW resonator transmitters which drift like Kon-Tiki with temperature and have a poor initial accuracy anyway. As SRD's are 99% cheap and cheerful devices, the performance is at the lowest level they can get away with, and as a result, they readily jam and are jammed by other SRD.

I don't know what bands they use in Oz, though, but the cheap and cheerful (i.e. basically sell crap) approach will be the same.

I have a hard time understanding how the current drain of an RKE receiver can magically be enough to pull so many ampere-hours out of the battery, though. So I suspect something else, and good spark's advice is something I totally agree with.

29th Aug 2011, 14:39
Offered in the thought it might help someone:

My Mercedes-Benz diesel once discharged it's fully-charged battery in a very short period - a few hours - while parked and as an engineer I couldn't understand where the energy had gone, leaving no trace.

Subsequently found to be a glow-plug relay stuck on: the glow plugs are one of the few things that CAN deal with a heavy discharge without "burning up" - way back in those far off days it sometimes took a minute of pre-heating in winter before the ol' cast iron lump would fire (but it always did, in the end).

DB changed the relay and the glow plugs, never happened again. These days diesels start instantly.......................