Glyn

Nik, lots of good advice here especially about the amp meter, if you use a volt meter the battery will always give the full 12 volt reading right up until just before the battery is completly dead, starting the engine and getting a 14.2 volt reading does not indicate your alternator is OK, the amp output is the important reading. The 12 volt car system is not really 12 volts, the alternator will output 15 volts or more, it has to, to get charge into the battery, think of the voltage as a sort of pressure, if the alternator pushed 12 and the battery was 12 it is a sort of stalemate, the push from the alternator has to be greater in order push charge into the battery. The switch over from battery power to alternator power is to the user invisible but all the time the electronics measure voltages, the alternator powers your car and pushes voltage into the battery when the output from the alternator exceeds 12.7 to 13.3 volts, output depends on rotational speed and load - ie what have you got switched on, the alternator is a complex device it has a series of diodes, (A diode will only allow current to flow in one direction) if a diode goes bad the alternator can draw current and try to behave as if it is an electric motor (it will try to turn itself) this will flatten your battery. There are 3 fields in the alternator all diode controlled, one can fail but the output with a volt meter connected to the battery will give the impression all is well, what is happening is that a pulse of charge is set up as one of the three fields is not working, voltage will look fine but the amperage output will be severly reduced, typically the starter motor will draw in excess of 150 amps when engaged - ohms law in which watts equals amps times volts - 12 volts times 150 = 1800watts - a lot of power drawn, also typically the battery is 80 amp hours (all batteries have a rating of amp hours) this means the battery will deliver 80 amps for one hour before it is flat, therefore drawing 150 amps to start would flatten an 80 amp hour battery in half an hour (if nothing else was powered by the battery - but other things are powered such as ignition and other circuits), however if the engine is cold, the oil thick the starter will exceed 200 amps and that is why you could not turn the engine in the real world for half an hour. Because of the initial draw of power to start, voltage is reduced to other areas of the car, this is counteracted by voltage stabilisers, most of the electrical equipment in the car is regulated to voltages between 5 to 10 volts so they contine to work when voltage is reduced - you dont want your water temperature or fuel gauge to read lower when the battery becomes discharged. (this is why i say the 12 volt car system is not really 12 volts) To get back to your problem, im not sure what equipment you have to test the system, a simple way is to remove the obvious - take out the bulbs in the two boots, fully charge the battery put a clamp meter over the positive lead (no need to disconect anything) the clamp meter will indicate what amperage is being drawn by the car, the reading should be very low, just milliamps, if above this disconnect one fuse at a time and recheck the meter - you will then be able to identify what is drawing the current- If this still does not find the culprit disconnect the electrical connection to the alternator - this will test the condition of the diodes - if they have failed and the source of your current drain. Sorry about the long winded reply Glyn

Spot on, i am in the UK, I didn't know there was a difference for something as innocuous as a cig lighter, why do they have so many specs? Glyn

The beam spread of lights between is different between left and right hand drive, On a right hand drive car the the nearside (left hand side from the driving position) headlight should throw a beam of light towards the nearside to highlight kerbs etc, the same is true for the right hand side for left hand drive cars, if you use the wrong type of unit the car will fail its annual MOT, A UK car being used in a country that drives on the right we have to fit defusers to change the beam spread. The light unit will look almost the same but internally they will aim the beams differently Glyn

The cig lighter only has power when the key is in the ignition, i have a satnav system hard wired and a road angel hard wired directly to the connections on the back of the lighter socket, so i can still use the lighter socket as well Glyn

Just to make sure everyone understands why the coolant would leak when only the cap was faulty. Water boils at 100C every one pound of presure raises the boil temperature by two degrees, all caps have a preset force when they will release excessive pressure, typically 15 pounds, this means water will need to be at 130 degrees before it boils. If the cap is damaged and no cap force then the water boils at 100c and expands, the expansion is vented underneath the car. Glyn just trying to be helpful, not showing off :clapping:

Never heard of that problem before so i would consider this is not a tendancy at all, Before you shell out have a look at the gearlever pivots (underneath the gear knob gaiter) they are just a plastic type material. give it a quick spray of WD40 and try again, if this corrects it then go back to the pivots and work some grease into them to make a longer lasting solution (WD dries up prety quick) Glyn

The hiss you describe i suspect increases with speed not revs, it is likely to be either a stone stuck between the brake disk (think you call it a rotor in the US) and the steel backplate, or wear in the bearings allowing the disk to deflect excessively When you stear to either side the disk deflects a little due to the forces acting on it and wear within the wheel bearings allow a little more movement, this does not mean your wheel bearings are shot, just lightly bend the back plate (splashguard) away from the disk a little. All disks run out of line a little and the hiss, hiss, hiss you describe is spot on for this problem, it is common with the boxster to get small road chips stuck close to the disk Glyn