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Battery, alternator, volts or lack of them...


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I have a VDO volt gauge in my 300tdi which reads 13v when running and never seems to go any higher, I would have thought 14+volts would be more like it.

I changed the alternator about a year ago – at that time the volt gauge was not fitted.

I changed the battery about 1 month ago but this has made no difference at all.

In the morning when I turn the ignition on but before it hits the starter position my gauge only reads 11v and I know I am not loosing and power when it is sitting as it often sits for two weeks when I am away to work. Still 11v.

Any thoughts – another new alternator or up rated alternator or a new regulator for the thing.

I do have a lot of power hungry items – light bar with 4 spots, two driving lights, winch and eberspacher but have not been using any of these while testing for voltage.

I may fit two batteries as what I thought was a faulty battery may not have been.

I did read somewhere on here that a Mondeo alternator may fit and provide 80 + amps, my alternator is standard as far as I know.



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Starts fine, usually on first turn. No I have not had a multimeter on it yet but will do in the morning.

It shows 11v before the starter is turned.

Exactly what mine shews....I wonder if that's because of the heater plugs and the stop solenoid

Funny I've not noticed it before.

What does it shew if you turn the key to accessories only ?

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Jason110 & Sirocco you were both spot on, nipped out to the garage and checked with a multimeter.

1. Ignition off = 13.5 volts, Gauge reading 12v

2. Ignition first click = 13 volts. Gauge reading 11.5v

3. Ignition second click and glow plugs on = 12.68 volts. Gauge reading 11v I thought the drop here would be more ?

4. Ignition to starter turning = 12.25 volts. Gauge reading just under 11v

5. Engine running = 14.25 volts. Gauge reading 13v.

Well just goes to show I was worrying for no reason really. The drop in voltage or poorly calibrated gauge was just a bit misleading to say the least.

Voltages were taken from my Anderson plug on the outside of the battery box.

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Wire the gauge directly to the battery, if it shares any wiring with other circuits (especially power hungry ones) the gauge will under read due to voltage drops, the greater the current flowing the greater the voltage drop. The gauge itself will take hardly any current so the wiring doesn't have to be heavy.

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As far as I remember I think I did the same as you, just connected to a white wire, Now I know it reads about 1 volt low I can live with it but if I do remove the raptor dash at some point I will run some new wires straight to the battery. As for the winch I have it wired through an isolater, which is turned off when not in use.

I was just looking at the x charge system which I may get at some point if my old battery fits in the box with the new one. Just for peace of mind and also to save wasting a good battery.

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with your winch battery voltmeter wired from the output of the isolator, you'll only see batt volts when isolator is on, I can see my winch batt volts while winch is isolated & engine is running, here's how the relay is wired, the text is how my old warning light was wired.


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