I've got a +Turbo'd 1992 740, with chipped ECU and EZK boxes. My electric fan has been refusing to shut off after the car engine was off (doesn't shut off after 5 mins, could run for hours if I let it). I've been disconnecting the batter for a 10 secs and reconnecting it to shut the fan off, but all of a sudden the fan stopped working completely. The only time it would work is if I tapped the fan controller relay (the one next to the battery), and it would come on without the key in the ignition.

So, I replaced the relay today, and now the damn fan won't shut off at all. The 10 second disconnect of the negative battery cable doesn't work either, it stays on 100% of the time on the low speed setting (goes to high speed with engine warmed up) unless the battery is disconnected.

The radiator I have is a plastic endtanked one with auto tranny cooling lines. There is no thermostat in the radiator or cooling hoses, there never was. The fan is a stock fan, came with the car and is not an addition.

What do you guys think? I'm not sure, I thought my chipped computers could be sending a faulty signal but if the key isn't in the ignition and the fan is still on it's got to be a short or something. I have no idea.