P38A Alternator not kicking in right away

Hi all,
When I start my 97 P39 (4.6 petrol), the alternator is not kicking in right away. The ignition continues to run off the battery, causing the voltage to progressively drop (probably not doing it much good). After a minute or so it kicks in suddenly and begins recharging the battery. I can't hear any belt squeal. Any ideas what it could be?
All the best,
Sam

Check battery & alternator connections are tight & clean.
Check belt is in good condition & correctly tensioned - it may slip but not squeal. (My RRC has done this occasionally)
If all else is OK most likely to be sticking brushes or a voltage regulator on its way out.

Sorry can’t answer your question but how do you know I’ve the alternator is kicking in or not mabey you can answer mine

5am. The alternator is unlikely not to be going round (unless you're telling us it doesn't....) you could pop the belt off and rotate by hand, just to be sure . I also vote dodgy VR. Had no end of trouble with wife's Audi due to the VR... but 4.6 much less sophisticated get a replacement VR for less than 20 quid. Search mobiletron on here, I did a post a while back with the part number you will need if you have the magneti marelli alternator.

Pete - if you watch the voltage drift down from 12 after you start then you can assume the alternator is not doing it's job - if it then jumps to 13.5- 14.5 then it is...although the 13.5 is low-end of the range. If you haven't already, grab yourself a cigar lighter voltmeter for less than a fiver off ebay. Worth it's weight in gold.

Or a multimeter set to volts DC across the battery terminals.
Check voltage with engine off then start & see what happens.