My 1950 GMC, model 253 with 228 engine and 6 volt system. Voltage regulator was not working so I replaced it this morning with a new standard VR -18 regulator, now it shows a large discharge when the key is turned off. And yes I polarized it. The old regulator was not charging the battery ( generator putting out 7 volts but from regulator to battery was .5 volts) and showed a small amount of discharge when key was on and no discharge showing when key was off. Is VR-18 the wrong regulator? And if so what would be the correct one? Or did I do something to cause this?