1988 XJSC Cabriolet V12 (Mfg. 11-87)

Taking off from my other thread on this subject.

I changed the thermostats to jiggle pins, topped up and bled the system. Previously I found that my overflow tubes and line to the tank in the fender well were clogged up. So I guess it was a pressure cooker though nothing vented from the caps either. Got all that cleaned out last week and went for a flawless 50 mile test run.

The next morning on the way to work I was at 3/4 hot again. WTH

When I jiggled the relay the fan would come on so I took the cover off the relay. The spring had come off the top of it. I reattached it and taped the cover back on. Ran the engine til warmed up (3/4) again and no fan. Suspected the thermo switch so I ordered a new one yet to arrive.

SIDE NOTE: Without the cooling fan running (jumper wire for now) the speedometer acts perfectly. Once the wires are jumped, speedometer jumps around. Before I got started I could jiggle the wiring harness and the fan would come on and the speedometer acted fine. A real pain in the *** to have to do every time you drive or park.

Uncovered the wiring harness and no visible signs of a short. Got a new relay which instantly blew the fuse (15 amp) which takes out the horns too. Tried all the way up to a 30 amp fuse and it blew that as well. Put the old relay back in and all is as it was.

TODAY: While working on all these issues simultaneously. My old fan switch decided to start working on it's own for once. From cold it didn't kick on til the engine was 3/4 hot. Still going to replace it anyway. When I topped up the system after flushing the radiators' core and fins as well as the engine, I bled the system enough to waste about 2 gal of mix anti-freeze.

At least now when I jiggle the wiring harness the fan doesn't kick on but the speedometer is still screwey. Did i miss anything?