Alternator weirdness

[Luvmeadeadpedal]

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Alternator weirdness
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Alternator weirdness
Postby Luvmeadeadpedal » Sat 07.01.2023, 08:33
I got my car running yesterday after the previous owner let it sit for 3 + years and all seems well except for the alternator light.

The car shows just under 14v on the gauge and I put a meter on that battery terminals directly and reads the same. I turned on that lights, fan, ac and volt meter still read 13.85 colts so definitely charging.

Does anyone know at what voltage the light in the instrument cluster activates?

Now other factors to consider

I started the car still torn apart from blowing out the fuel line and swapping the fuel filter and the convertible top lid was propped open while I checked for leaks ( not that it would matter but who knows ) Could a loose battery terminal cause this?

Let me know if you have a thought here on this.

Next up I tackle refreshing the brakes.

[Saltire]

I got my car running yesterday after the previous owner let it sit for 3 + years and all seems well except for the alternator light.

The car shows just under 14v on the gauge and I put a meter on that battery terminals directly and reads the same. I turned on that lights, fan, ac and volt meter still read 13.85 colts so definitely charging.

Does anyone know at what voltage the light in the instrument cluster activates?

Now other factors to consider

I started the car still torn apart from blowing out the fuel line and swapping the fuel filter and the convertible top lid was propped open while I checked for leaks ( not that it would matter but who knows ) Could a loose battery terminal cause this?

Let me know if you have a thought here on this.

Next up I tackle refreshing the brakes.

Well . . . The ‘no charge’ light (as Lotus calls it) doesn’t activate at a specific voltage as such. It has two connecting wires. One comes from the alternator, and one is driven by a 12volt ignition controlled supply via an instrument panel connector. Both cables therefore supply a positive voltage to the light. If there’s a difference between the two voltages (as would happen if the alternator failed), the light illuminates. Conversely, when the two voltages cancel out, the light extinguishes.

Have a read of the Electrical Manual (see the “Manuals” link at the top of any forum page), specifically section MJ17, page 36, which relates to the alternator. Wiring diagram 2, further on down in the manual, shows the cabling. Also have a read of this thread, which discusses the alternator in more detail.

Without seeing the car, it’s hard to be sure, but I suspect the regulator pack on your alternator is on the way out. Simon_P on this forum does (or used to do) an alternator service pack for our cars, which may well solve the problem if I’m correct.

Good luck!

[Luvmeadeadpedal]

Thanks for the reply.

Will carry my jump box and see if it sorta itself out or if I need to just swap out the alternator. Seems either way rebuilding or replacing will be the same labor.

Dave

[peteoddcar]

Does the alternator light illuminate with ignition on - engine not running?

[Tuga2112]

Does the alternator light illuminate with ignition on - engine not running?

i wouldnt rely much on that light.

mine goes off when you put the seatbelt on.... and remains off even tho the alternator aint working.
just another one for the to do list on mine.

[peteoddcar]

Does the alternator light illuminate with ignition on - engine not running?

This is important for the function of the lamp - if it does not illuminate on ignition on with engine not running then this indicates a field diode or regulator problem - so the light does have a proper function if yours goes on and ofc with the seat belt something is up in your cars wiring or instrument pack