also see upkeep and performance hints on our message board at board.mgclub.org
Q: I have an electrical problem with my 1973 MGB roadster. I have no electrics at all. I thought I had a bad battery so I purchased a new 12 volt Duralast battery from Autozone and still have no electrics. I purchased a new ground cable, cleaned a new spot on the battery frame and bolted the cable to the frame. Still nothing. I took a set of jumper cables and clamped one cable to the negative side of the battery and the other end to the car and still no electrical. I have no head lights, horn will not blow, wipers will not work, etc. I tried clamping the cable to a lug nut, the leaf spring, bumper support, etc. and still no electrical.
I have checked all fuses and do not know what to try next. I am open to all suggestions.
Try putting a meter on the cable where it connects to the starter to ground and see if you have power there. If no power, the positive cable is probably at fault.
If there is power, the cable should be good. So next, try putting a jumper on the starter between the ignition switch connectors (the 2 small blade connectors on the solenoid).
If the starter turns over, the problem is likely in the ignition switch itself. The switch is itself is small device on the left side of the steering column/back side of the lock inside the plastic column cover. This is prone to mechanical wear and the casing loosening-up over time.
Once this happens, the contacts fail to connect and the car has no power. In the extreme, the plastic back cover comes off the metal case and the switch falls apart.
Replacement units are available from the catalogs, though these have one wire less than the original unit (I think it had been for the ignition lock-out from the seat belts), but it works.
I hope that helps you. Let me know how you make out. Good luck.