Removed and cleaned pos battery lead a few weeks ago and it cured the "light on"problem,but its just happened again It seemed to occur when I switched on the A/c Is that coincidental or an issue to be concerned about? I ran the engineers test and battery level 11.2v no increase with engine revs,light remains on Is it worth cleaning lead again? Thanks for your help...

 

You could try cleaning the leads and then run engineers test again. If it isn't up to voltage then it would sound like alternator replacement time.

 

11.2 actually could be a bad battery, as well. Have you had it load tested?

 

11.2 is near dead.

 

After full charge,battery reading 12.2v After operating starter motor dropped to 11.8v,then recovered to 12.2v again

 

If you are only getting 12.2V after a full charge then your battery is goosed. What voltage are you seeing at the battery terminals with the engine running.

 

Do not have facility to test voltage across terminals,figures I gave were from Engineers test result

 

Replaced battery,it was borderline...Tested voltage across disconnected battery,12.6v...Tested it running about 3000rpm voltage dropped to around 12.1v or less, and battery light remains on....could that be bad pos battery lead?

 

If you're seeing 12.1V with the engine running then it's time to get a new alternator. That is why the light is on, it should be around 14.1V with the engine running.

 

You are not going to be able to successfully troubleshoot this problem without a multi meter. The voltage at the battery for a little after starting should be around 13.5 volts to restore the battery after starting draw.
With the vehicle running you need to test the output of the alternator at the main post output. With the voltage dropping from 12.6 to 12.1 the alternator should be putting out in excess of 13 volts.
If you can determine that it is then the voltage drop is in the cable. If it isn't then the most likely is the alternator is bad and needs to be replaced.