I would guess the alternator is trying to run a maximum capacity, thats
usually why they get hot, if you put the alternator on, take it back to
the parts place you got it and have them warranty it, if you had a shop
do the reapirs a year ago, you should still have warranty on it.. ps
the light may flicker if its overcharging as well as undercharging.
usually the regulator internally is bad.
Good luck.
Badly, the diagrams and additional specific information about Jaguar models is less that so much people thinking. I suggest look some Haynes manual os visit the local library to find some Workshop manual.
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Your alternator responds to demand. 13.5 is a normal charge rate. 12 seems low. Charge rate is governed by the voltage regulator but it responds to what the battery is requesting. Make sure that the wiring going to the alternator is not loose and that it is actually receiving a good connection between it and the battery (B+ wire). Also load test the battery to make sure it does not have an intermittent open connection inside. Your problem could be either a bad connection, a partial disconnect internally with either a diode or the regulator, or a battery problem.
Always test with a fully charged battery. Test with all accessories on and again off. Compare your results. At no time should charging voltage go below 12.5 and it should vary between that reading and 13.9. When running for fifteen minutes, it should not progressively drop off below the low number.
Bench testing sometimes is good to get an idea of if the unit is mechanically sound but in car testing reveals more about how it operates in "real life". How it operates after a rebuild often also depends on exactly what was replaced during the build. End bearings, regulator and all other removable internal components should be replaced. Some shops only replace what they see as failed.
Without personally being there to test what you have, I've attempted to give you some direction.
Hopefully by checking what I've mentioned you will find the solution.
Any alternator can test good and still not put out a charge. one of two things can go wrong. Poor connection(s) or a defective diode in the alternator. Do a test with this on the car. Start the engine and connect the volt meter to it to check the voltage. It should read good as you had stated. Next remove the volt meter and set it to the AC mode. Now connect the meters probes as so..... the negative probe of the meter to the positive battery terminal and the positive probe to the negative battery terminal. If you receive the same reading the diode is at fault. Diodes keep the voltage running one direction which is for direct current. If bad it will alternate instead as a result in this test. Thus if alternating no charge will become to the battery
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I should have added that this is the second regulator. Also the alternator is not at max capacity (behaves the same whether everything is on or off). My biggest hurdle is trying to troubleshoot without any kind of manual or schematic since I cant seem to find any resources online.
Having issues the my alternator. Replaced the regulator twice and then had the entire alternator rebuilt. What has happened is that after installing new rebuilt alt. it seems to work fine for the first few weeks. Then the charging voltage drops (12-13.5 volts). I'll replace the reg. and then back to the same thing again (works well a few weeks and then drops off) I'm thinking maybe I am not getting the right signal from the 2 pin plug that the alternator plugs into, but without a schematic I'm not sure what to expect. I've measured both connections and get 12 volts on both (is this correct? ).
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