1995 Discovery TDI electrical problem with air con. Fans come on with ignition, ac switch has no effect.

 

Do they even come on when the engine is stone cold?

 

Yes. Fans come on immediately the ignition is switched on. I had extensive work done eg new head and suspect something has been hooked wrong but I can't find it.

 

Take it back to the shop that did the work, they messed it up they should correct it.

 

head work really shouldnt have damaged the switch.. But thats probably what it is.. The switch.

 

Work was done abt 2000kms away therefore impractical

 

Well then it has to be a bad switch or sending unit.
If the ECU thinks the engine is overheating it will turn those fans on.
If the ECU thinks the A/C is on it will turn those fans on.
I would turn the key on and the A/C off and then with the fans running unplug the engine temp sensor, if they shut off replace that.
If they stay on plug that back in and then unplug the A/C compressor.
If they once again stay on then I am out of idea's.

 

Thank you Spike. Following your advice I eventually found that the person who replaced head etc had reversed the two similar sensor plugs below the thermostat. When I pulled one the fans stopped. I changed them over and , bingo, everything was back to normal. Thank you again. colanne.

 

Thank you for posting fix.
Now if someone else has a similar problem and they do a search maybe this will help them.