Everything works fine with the key in acc. position, but when I start it every thing stops working. No lights, no radio, no heater, no nothing. Any thoughts?
it could be your problem with alternator (charger) circuit to battery or your switch problem.. try to change your switch to generic one (buy one from local shop) cheapest one but please do not throw away your original switch first.
disconnect your battery, change switch with original cable intact with same position on switch, connect the battery, try that.
if the problem still occurs, try to remove every cable on acc try just one cable like lamp first, start again. if the lamp can be turn on, than then the problem comes from the rest cable on acc.
usually old car have problem with electric being jumped by another cable or short circuited.