2001 Toyota corolla fielder charging light.

Charging warning lamp has come on, have tested voltage at battery with car off approx 12 volts, car running 13.5 volts. Have been using car for past week including at night with no issues apart from charge light staying on. Have also tried swapping alternator with one from a dismantlers and same deal, light remains on. Does this warning light which looks like a picture of a battery have some other function apart from indicating charging system / alternator malfunction. Model of car ZZE 124, engine 1ZZ FE , 1800cc VVTi.

wiring diagramm would be needed. also serial codes from diagnostic port with tis-techstream or other oem level diagnostic tool might hint at a clue .
a fault in the wiring system or something could make the battery light glow on dash also its why you would look on a wiring diagramm as to where the wires go and what they do.

areffer- My first thought was dodgy battery or dodgy alternator.
Given you have swapped out the alt then Im thinking look at battery terminals.make sure they are secure (tight) and nothing you can see is broken.
Once you have done that then do you have the option of swapping the actual battery even for a couple of minutes.?
Youll find that as a temp measure even a battery with opposite pole position will still JUST get positive and negative terminals on.
Start the car and see if the light goes out.
beyond that simple stuff then Im with intrade. It needs wireing diagram

Thanks for the replies. Will try swapping battery for a known good one and check terminals etc. Does anyone happen to know if I unplug the connection terminal from alternator ( the one with 3 wires ) should the warning light go out then? My understanding is it should.

Don't unplug it while the engine is running. Alternator might go "open loop" meaning it will try to output max voltage and current. Doubt that the rest of the cars electronics could handle that.

You need to do some volt drop tests. The alternator might be working fine, but if the wiring can't carry enough current to the battery then of course it wont charge properly. Also had the same problem caused by loose bolts between the alternator and the engine block. (not enough current could flow in the ground side of the circuit).

well i own a 1992 fiat 1.7 diesel and it has the charge light glow at times the problem is the wire on the alternator goes direct from the alternator to dash cluster to turn off or on the charge light. The therminal seems slight loose corroded so since i knew what the problem is i have just ignored it . It has no computer on a old diesel and only 1 wire makes the engine stop or go. the fuel shut silanoid, on a petrol with computer it could be the same way wired or it could be feeding in to the main engine computer and the computer then turns the light on dash cluster on or off older toyota are quite simple. with newer cars this light goes to a minimum of 2 computers whom all make desitions to turn the light on or off and on smart charger like2005 nissan ford etc this signal goes to the transmission and loads of other computers as it must turn the alternator off while battery is full and when you demand full power and try and charge it on down hill overrrun .
that all wont be the case the most it can be that it feeds the engine ecu and the engine ecu turns on the instrument light on a old toyota,, its why i said you want to see the wiring diagramm , and of course you need to learn how to read a wiring diagramm.

should the warning light go out then? My understanding is it should.

your wrong the light is out when the alternator tells the wire its charging on older alternator. poor contact on my fiat alternator makes the light on dash glow, i wriggled it and it came right but i dont want to fix things that still work fine , you can get away with stuff like that only on old cars only.
modern car would go in limp home with that problem or a minimum a check engine light be permanent on on a 2005 nissan ford with smart charger.

Thanks for your input intrade. I have no problem reading wiring diagrams, may have more of a problem trying to find one for a jap import. Will have another look at car tomorrow and try good battery etc. Also will unplug terminal on alternator and identify which of the 3 wires does what, from what I understand 1 will be the sense which is permanently 12V , 1 will be fed 12V through ignition, and the other will be the warning light wire, will use a test lead with bulb in circuit to identify. I could be completely wrong in my thinking as I am more used to dealing with older vehicles without all the modern electronics.

Check the fuse labelled 'ALT S' located in the fusebox in the engine bay. If this is blown or faulty then it will cause the battery light to light up on your cluster but the alternator could still be working perfectly. I had this problem on my '06 Toyota Aurion the other week when I was trying to diagnose an unrelated problem and accidentally put that fuse back in the wrong place, which caused the battery light to come on. Even if you just try swapping it with another fuse it's worth checking before investigating further.