caterham weak electrical system

[twobone]

I bought a voltage multi-meter yesterday.

Battery shows a steady 12.4 volts.

At 1500 RPM+ the alternator is feeding 14.5 volts to the battery.

With the headlights on high beam the charging voltage as measured at the battery drops down to about 12V

 

However, when I turn on my headlights, I get a marked decrease in my idle and the car labours a bit. I have a new coil so that's not the problem.

 

I will clean up the headlight switch connection next in case it is loose or dirty.

 

I'm a bit surprised that the headlights would have that effect as there is nothing else being powered within the system other than ignition.

 

I fear that my distributor arm might be on the way out

[turboeric]

Let the Lucas jokes begin!

 

Seriously, there's volts getting to your battery and lights, but not amps. (gross oversimplification). Sounds like you may have a dodgy ground in there somewhere, or your alternator belt is slipping.

[Klasik-69]

Lucas jokes aside, I agree with turboeric regarding the ground. Make sure your car has a heavy gauge ground cable that runs from the engine block to the frame, and from the battery ground to the frame or engine. My ground cables are from the battery ground to the engine and from the engine to the frame, each being a heavy gauge cable. If all the grounds are good, and the connectors on each end are good, make sure your battery is also good. A weak or marginal battery may be causing the alternator to work hard enough to put an additional load on the engine and slightly lower the rpm. 40 amps @ 12 VDC equals 480 watts, or 0.64 horsepower. I don't think a drop of voltage is reducing the ignition capacity in any way, more of a load being applied to the engine.

 

One more thing to check is for a short inside the headlight. On my 04 Caterham, one of the wires inside the right headlight had become chaffed and was grounding out intermittently on the attaching mount. Hit a bump, blow a fuse. Also had no ground on the front turn signal lights. Fixed that and now all my electrical functions work. But if this is a Lucas system..............how long will it work ?

 

Mike

[TheDingo8MyBaby]

In addition to the suggestions above, have a look at the alternator wires/connections. The heat from the header on a xflow tends to degrade the wires/connections over time.