Now what?

Charged the battery last night, don’t know to how much other than 11.8v coming off the terminals according to the multimeter.

Today, I’ve put the coolant system back together as the new parts aren’t coming until Tuesday, this way I can check that the inlet manifold repair is good.

Battery wasn’t dead, central locking unlocked this morning, good news. But must be draining somewhere, but again I don’t know how charged it was last night as couldn’t attempt to start it without an intact cooling system.

So, coolant back, booster pack on, turn key = vroom. Voltage off alternator terminals = 13.8V, pretty constant even with revs, same voltage at battery when motor running. Ran it long enough to get coolant+flush stuff hot, good news, no sign of water leak from inlet manifold :woot:

Bad news, battery dead, I mean not enough to turn starter. Have I just been unlucky and have a short-life battery and all the other things masking it? Would a short somewhere show in some way with the multimeter. I’m going to now remove the new electrical stuff, the subwoofer and unplug the stereo ISO leads, and then try again. I kept my last battery as I wasn’t 100% sure it was dead, that has the battery charger on it at the moment.

Before I put the steel toe caps on and play football with the car in frustration, any ideas?


The 13.8v at the terminals seem to suggest it’s charging OK. Either it’s a duff battery or you have a current drain somewhere. Try disconnecting anything on a permanent live feed individually to see how the battery holds power. If its only started recently, could be the new sound system drawing too much from the battery and the alternator can’t keep up. Similar to using the heated rear window, heater, wipers, etc in winter, but only doing short journeys.

new stereo unplugged, going to get LED lights for the interior.

Battery with -ve disconnected = 11.8v but almost dead, connect -ve and watch the voltage drop. Going to try it with the fully charged spare tomorrow.


If the voltage is dropping with everything turned off you’ve got a drain somewhere in the system.

My old Reliant (yes, completely different kettle of fish I know) had a drain somewhere - it would charge fine with the motor running, but when I turned the engine off the voltage was constantly dropping. I had to disconnect the alternator wire from the battery every time I got out as that stopped the drain… never did get to the bottom of it before the car had to go.

cheers for that :bondage: :haddock:


If it drops when the -ve is connected it could be an earth connection corroded somewhere. Check the various earth connections to the body, especially in the engine bay.

overnight test, one fully charged battery into the car, the one I removed and replaced with the new battery as I thought it was dead. Three weeks later I fing the receipt for it, less than 18months old :lol: could still be dead, but seems to be holding charge. The self indicator thing hasn’t gone green though, but I guess it’s beer o’clock again and see what happens in the morning. The alarm, clock and stereo are expected to pull a little, the subwoofer and amp are disconnected. Can see any corrosion on the engine bay earths, wondering about the reverse switch, so removed that connection as well, even though it doesn’t go live until ignition set II.

Tomorrow is another day, if she starts, she’s going through the Woodley ford a few times now we’ve had some rain, might clear off the mud so I can have a decent look underneath :smiley:


If it’s losing charge overnight, it will only be something on a live feed or duff battery. Used to have a customer whose battery would go flat overnight which turned out to be the battery discharging when it got cold. Fault in the battery itself. Kept it in the garage overnight to prove the point.

During my army days I was in charge of the battery charging shop - the symptoms you describe were fairly common - the battery posts and clamps become high resistance - whilst running the engine check the voltage at the clamp and the post - poke them with something pointy to break the surface , if they are different, the conductive surfaces of the posts and clamps need to be abraded back to shiny lead and coated with Vaseline or similar - the dull grey surface can become a relatively high resistance mixture of lead oxide and lead sulphate or other combinations depending on the contaminants, this effectively increases the ’ internal resistance’ of the battery greatly reducing both the charging and discharge currents (basic ohms law) . the self indicator thing as you put it, is a very simple hydrometer, it bobs to the top when the correct S.G. is reached - if you cant see it it isn’t charged - taking for granted there is enough acid in it - top up if possible with distilled or deionised water only the liquid MUST cover the plates.

cheers Mortlake, I’ll give that a check

If the battery seems OK, take the battery negative wire off and connect an ammeter between it and the battery negative post (don’t try to start it :chuckle: ). Idle current will normally be less than 50ma. If it’s more than this, selectively pull fuses until you have found the culprit circuit.
It could also be a diode in the alternator :(- seen this one before.

result fully charged battery left in overnight, walked out this morning, car unlocked, battery voltage unchanged and started first time.

So now to start plugging things back in one at a time, I’m guessing it’s the “made in China” app that’s on the sub, so I’ll just add a seperate switch for it. Going to give the terminals a clean as per Mortlake post as well, must be due that anyway at this age of motor :slight_smile:


The 700w sub I fitted to pinky had a separate control feed to turn it on which operated a relay inside the amp to shut it down, does your sub have anything similar ?

yes, the magic blue wire on the stereo that should mean it only pulls when the stereo is on, not convinced. But that is now two runs out with the battery I removed when a brought a new one, that I charged to max. I’m guessing a slow drain somewhere that I’m simply never going to find. Now I know I have two good batteries and they last a while each, it’s a five minute swap over - sound familiar? :wink:


:idea: all you need now is a relay to have the batteries in a parrallel circuit so that one charges whilst the other is draining :Plot: de ja vu?
oh and you have to learn to drive witout headlights but everyone else will have there on so just use there light