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EP3 Battery light on, headlights dimming at lower revs

Topjacket

Topjacket

Messages
96
Hi all

About 2 months ago the battery light came on in my 55 Plate EP3. It was on every time I drove the car. Then around 2 weeks later the light just went off and has not been back on since. When the light was on I tested the battery with a multimeter both when the engine was and wasn't running. All the numbers were absolutely spot on where they should be (according to a youtube video I watched).

Although its good that the light has now gone off it is annoying as I there was clearly a problem but can't think how I have a hope of finding out what it was. There are 2 issues that I seem to be left with now, when stationary if I rev the engine the lights will get brighter and then dim when it goes back to idle (I dont remember this happening before and my other car doesn't do it). Also the passenger door doesn't always unlock. I would say it works about 80% of time.

Does anyone have an idea of what might causing this or have experienced the same? The battery is only a year old and the alternator seems to be working as it should. From reading other posts online the dimming lights could be caused by poor earthing. Does that sound right? Does anyone have a view as to whether an earthing kit could be worth a go in this situation?

Thanks in advance for any advice.

Cheers

Jim
 
What's the voltage reading you're getting at the battery with the engine running with all loads (lights, heater fan) off and loads switched on (lights on inc. full beam, heater fan motor on full speed)?


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Hi mate.

Thanks for coming back to me. When everything was on, full beam, heater, radio, it was reading 13.7. When it was just idling without anything else it was reading 14.4.

Cheers

Jim
 
Well your voltage readings are absolutely fine so we can assume the alternator is working correctly.
It does sound possibly like a wiring/earthing issue. Does all the lights including interior lamps and instrument back lighting dim and get brighter as you rev the engine?


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The instrument panel does dip but doesn't seem as extreme as the headlights. The heater fans are also affected.
 
Hi,

You should check the ELD (Electrical load detector). A faulty ELD would cause just the symptoms you describe. Also if you have aftermarket audio equipment (or any other bigger electrical load) connected directly to the battery, the ELD doesn't know about those and can't boost the charging to compensate. Always a good idea to check the ground cables as well.
 
Thanks Eddie

Is there a way of checking the ELD or would it just be a case of changing it and seeing if that fixes the problem?

Cheers

Jim
 
I think there's a checking procedure in the work shop manual for the ELD but it's cheap and easy to replace.
 
From what you say what you are observing is perfectly normal and can be seen on almost all cars. An alternator cannot produce its full rated output at idle speed so if you stick on a 50amp load to the battery (headlights, heater and rear screen) the voltage drops and the battery takes the strain. As the revs increase the alternator output increases in current and it starts charging the battery again. If the headlights get brighter and brighter as you increase engine speed above 1500rpm then the voltage regulator is fried. Sounds like your car is behaving itself to me.

crowds
 
Thanks Both, I really appreciate you coming back to me.

I think I will just get myself a new ELD to make sure as they seem cheap and easy to change. My other car definitely doesn't do this so it does make me think something isn't 100% right.

Cheers

Jim
 
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