I had the same problem, turned out to be the water pump, it would only blow warm at top speed, as the pump had only a few 'paddles' left and hence poor water circulation. if your's car is at about 90k you will need to change the pump.
Mark
May 2005
This is a common fault on the 90's Laguna, it's the resistor pack blown, hence only the highest speed (which bypasses the resistors) works. You can reach it by removing the glovebox, it's about £50 for the part. It'll last about 18 months before you need another if mine was anything to go by...
Colonel Blinky
April 2005
on my car it was coz the blower fan bearings were shot....get it fixed asap else fan will jam, thermostat will send more and more power to try to spin the fan, then the wiring loom will burn out....bout 1.5 grand to get put right..hundred quid to replace fan NOW
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