Heater/AC fan not working by quebecplatoon

Hi all i have a rover 75 2.5 v6 with a heater/ac fan not working on any speed atall,iv checked all the fuses and relays, all are ok but still no heater iv been told it could be the transistor and iv also been told it could be the heater motor aswell ?
any advice would be welcome

Posted 05 Nov 2012, 08:11 #1 

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It's probably the fan packed up. You will have to strip out the unit and then put a Volt-meter on the supply wires. If you have 12 volts on the supply then the motor will need stripping down to find out whether the brushes are worn down. If so, replace them. If no 12v to motor supply then the control module has blown.
Some times the plug on the PCB (Printed Circuit Board) board of the control module can cease to contact due to corrosion, the copper turns green; release the plug and clean the edge of the board contacts with electrical cleaner (carbon tetra chloride) and refit it. It has worked for me on many an occasion.

Posted 08 Nov 2012, 16:23 #2 

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I assume you mean the fan INSIDE the car, not the one in front of the car?

Do you have Automatic Temperature Control (digital display) or manual air conditioning?

In a 75 it's probably ATC (Automatic Temperature Control), so check the fuse link 10 in the underbonnet fuse box. The brown blue wire then takes power to the blower itself, check this as suggested above but it will only be live when the ignition is on. If theres no power it could be the fuselink, or a relay in the passenger fusebox. It could be a wire from the ATC controller to the relay. This is all unlikely, but check it first.

If that's OK, check the voltage out of the other side on the plain brown wire. If this is all OK, the main supply and connections to the blower are OK. The brown wire connects to the power tranisitor, which also has a big black ground wire that should be checked.

There are two control wires from the tranistor module to the control unit itself. It's unlikely to be these, but worth checking anyway that the wires are still plugged in.

Finally if none of that, it's worth checking the fuses to the ATC control. These are fuses 4 11 and 33 in the passenger if you have the older grey fusebox, 11, 27 and 34 on the newer red boxes.

Posted 08 Nov 2012, 19:48 #3