Crossflow and electrical questions

[robert green]

A few queries about my car - I have just fitted a Caterham supplied altenator which differed from the original having only conections for the three main wires at the back. I therefore had an additional wire which I have been told might be a trigger and I have taped it up. The ignition light functions and goes out on start up - is this ok I think the altenator supplied is a 55amp hour unit, although caterham told me it should be a 45amp hour and that is what I have been invoiced for - is this ok or may I be putting too much current through the wiring?

 

Finally, I notice I have a slight weep on one of the welds on my sump. Is this something that will require immediate attention or can I just keep an eye on it and oil levels and wait until I next change the oil in order to remove the sump and weld it up. Ie is it likely to make itself worse rapidly???

 

Thanks and sorry for what are probably silly questions!!!

[Graham Sewell]

Alternators supply current as needed - so although yours CAN supply 55A, it is unlikely to supply more than 10A most of the time.

 

Provided the weep is minor - leave well alone. The oil is a rust-prevention for the engine bay.

 

If it uses more that 0.5l (half the dipstick hashed zone) per 1000mile then get it looked at.

 

Low tech luddite - xflow and proud!

[Chris W]

Robert

 

A good check to ensure your alternator is working fine is to measure the battery volts with the engine OFF (~12.5v) and with the engine running at low revs (~14v). Start the engine but don't rev up, just let it tick over. The ignition light should go off and around 14v should appear across the battery as I said. Then get someone to rev up to say 3000 rpm while you monitor the battery voltage again. It should stay substantially around 14v.

 

If the alternator passes all these tests, you can bet it's doing its job 100%.

 

Don't worry about its being a 55Amp jobby, The only time that it has to supply any significant current is just after you start the car in order to replace the charge lost (probably around 15A) and when the headlights/sidelights are on (again around 15A). So it rarely has to supply anything even close to what yours can supply. The wiring will be just fine as the cumulative current (ie: the sum of all the currents needed by the various devices) only has one common cable, viz: the very thick red cable going to the battery.

 

An alternator supplies ALL the current needed once the engine is running, NOT the battery. It would be only in an extreme case where there was so much load on a smaller alternator that it could not supply enough current that the battery would have to start supplying the deficit.

 

Chris

 

2003 1.8K SV 140hp see it here