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electrical gremlins


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Good afternoon.

My long serving CSR has decided to test me. with a intermittent fault. (Then permanent).

No output from the Alternator Digital Volt Meter indicates 12.6V at battery terminals and at power output terminal of Alternator.

When the key is turned to on position No battery symbol is displayed and the oil pressure symbol comes on momentarily then extinguishes at this point the car can be started on the button and runs without hesitation.

Is there a drawing available so that i can trace there common point.  

Is there any connection with the ante theft fitted by Caterham.

Your thoughts please.



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Did the ignition warning light work OK until recently? On with ignition ON and then OFF as soon as the engine starts?

How many wires are connected to the alternator, and what colour are they?

What's the voltage across the battery at 3,000 rpm?

Any recent work on the car?


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Ignition light has always worked until this fault occurred. On with ignition ON and then OFF as soon as the engine starts.

Raising engine to 3K dose not alter the output 12.6V steady.

The symptom of the oil pressure symbol going out within 1 second without the engine running is the strangest point.

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"Raising engine to 3K dose not alter the output 12.6V steady."

That sounds as if either the alternator or its wiring is duff.

I don't know what was fitted to CSRs, but I'd start by checking all of the relevant wiring and connections including the engine earths. Inspect, wiggle, disconnect, clean, reconnect. That should identify the thin wire to the warning light and whether there's an exciting wire.


PS: Has the battery ever gone flat? And do you charge it whenever it's back at base?

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Thank you for your suggestions, The test of the supplies to Alt power in has been tested and the unit removed and mechanically driven with a proven winding voltage. This gave a output of13.66/14.02 volts output ( Alt is therefore serviceable) 

It is the lack of supply (12v) to the unit when fitted in the car that appears to be the problem. Its this source that i am attempting to pin down.

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The failure of a constant supply to the Regulator within the Alternator, was the cause of the intermittent charging and likewise the erratic light  indication on the dash. (battery symbol) 

The pair of wires (ing feed to Regulator and dash indicator). Pass between the Supercharger and the block,although the readings appeared within tolerance. Once the harness had been removed there was evidence of a fatigue fracture close to a fixing point. (replaced wiring in harness) 

As to the oil light symbol going off before the engine was started a lose connection on the multi plug was problem.

I placed a D.V.M. connected to the power socket and monitored the voltage during a 20 Mile trip.

Battery volts engine off 12.7V

Tick over 900 RPM       13.72V

3000 RPM                     14.10V

3000 RPM Head Lights 13.21V

Thank you for your help.



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