So fiddled with the aeriel some more today, disconnected the alternator and ran the engine, checked the wiring on the igniter noise filter, all seems fine but still good signal engine off, rubbish engine on.
Disconnecting this plug makes a difference, the signal is rubbish engine on or off! So I cleaned up the terminals and it made no difference, decided to take out the aeriel and see what was going on with it.
Turned out to be a big job, had to take out the air con evaporator, heater box, heater blower etc to get the cable out through the bulkhead...
Many rotten connections. Cleaned up the connectors and all the earth, then did the thing which I should have done first, checked for continuity between the mast and the connector which goes in the radio, there was none.
Tried to clean up the mast and connections in the mast, but no use, then broke the tube trying to dismantle it, turns out the tube with cable is about the only piece you can't get seperately.
Cut the cable up and found the break in the wire.
Somewhere in here, typical. The electric antenna is wrecked unless I can find a replacement tube with cable but it doesn't look likely as it's a special shape at the top with the coax connected to it.
Going to go to mole valley and see what they have tomorrow, if not might get a toyota antenna from eBay and make something up.