Hi, my name is Mike.

I have a 2007(57) plate fiesta 1.2 Style with 84000 on the clock. Its mainly a spare car for me and my family so it doesn't get used very much.. About 6 months ago the red battery light came on, shortly after that the battery died. I bought a new battery and after a couple of weeks the same thing happened. Now have a permanent red light on and the battery runs flat after a couple of weeks. Interestingly if I run it up to 2500 revs for a few minutes, the light goes off and the engine revs immediately increase to over 3000rpm. Come off the throttle and a minute or so later the red light comes on again.

Using a OBD-11 tester it only shows a P300 (H02S) Heater Control Circuit fault. Don't know what this is or how to rectify it, but.. is this the cause of the problem I'm having?

Hi welcome

12 minutes ago, Winkle Bill said:

Hi, my name is Mike.

I have a 2007(57) plate fiesta 1.2 Style with 84000 on the clock. Its mainly a spare car for me and my family so it doesn't get used very much.. About 6 months ago the red battery light came on, shortly after that the battery died. I bought a new battery and after a couple of weeks the same thing happened. Now have a permanent red light on and the battery runs flat after a couple of weeks. Interestingly if I run it up to 2500 revs for a few minutes, the light goes off and the engine revs immediately increase to over 3000rpm. Come off the throttle and a minute or so later the red light comes on again.

Using a OBD-11 tester it only shows a P300 (H02S) Heater Control Circuit fault. Don't know what this is or how to rectify it, but.. is this the cause of the problem I'm having?

The flat battery problem sounds like an alternator problem to me.

Measure the voltage across the battery terminals using a multi-meter. With the engine running, you should get around 14 volts (13.8 to 14.2 is what I would expect). If you are not getting this, then the alternator & wiring needs further investigation.

The heater control fault could just be down to the battery going flat, triggering a fault code. Check & sort out the alternator/battery problems, then clear the code and see if it comes back.

In addition to above, as your new battery has gone flat, would be wise to charge it back to full capacity using a 'smart' charger for at least 12 hours so proper diagnostics can be carried out.  If you don't have a charger, we can recommend a budget one if you ask...

4 hours ago, Winkle Bill said:

Now have a permanent red light on and the battery runs flat after a couple of weeks.

The alternator has failed.