Triumph Repair: alternator, lucas alternator, battery voltage

Question
I hooked the battery up backwards.

The ignition light is staying on so I expect the alternator is damaged.

Is it fixable or should I just get a new one.

It is a 79 Spitfire.

Thanks

Answer
Hi Steve,
You may have damaged the alternator but run a test before you purchase one. Check the wires to the alternator first.
Turn the key on and note if the "Ign" light is on. If so put a volt meter across the posts of the battery and read battery voltage. Then start the engine and note if the "Ign" light went out. Also set the idle at about 1500 RPM and read battery voltage again.
If the "Ign" light went out and the 1500 RPM voltage is 13.8 to 14.5 volts the alternator is OK. If the light didn't go out and the voltage at 1500 RPM is close to what no run voltage was you did damage the alternator.
Connecting up a battery backwards can damage an alternator diode pack and/or a regulator. Most alternator shops can overhaul a Lucas alternator.
Howard