Last update:

08/03/2005

  A/C Thermal Fuse

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Cars affected: All Scorpios  with A/C ( not fitted with Climate Control)

Symptoms: interior fan (blower) runs in switch position 3, it does not operate in positions 1 and 2.

Fault: thermal fuse defect

In my case, my blower was working normally in positions 1 or 2 and then suddenly it would only work in position 3.

Fault description: On non CC fitted cars, the blower is controlled by a set of wire resistors that drop the voltage for two of the positions (1 and 2) which results in the blower fan operating at reduced speed. The resistors are bypassed in position 3 for full speed operation. In addition a thermal fuse is fitted to prevent overheating of the resistors should the fan motor stall. In my case the thermal fuse in the resistor-pack was at fault.

Solution: I purchased a new thermal fuse from a spares shop for domestic electrical appliances such as coffeemakers and hot water boilers and soldered it in place of the old one.

Cost: about 1,50 (1.00)

Where can you find it and how does it look like?
Under the bonnet in the engine room near the windscreen in the middle, you will find a round cap about 15 x 5 cm in size. See photo (left hand drive car)

Pull it off, you will then see three connectors. Make a note of their positions (strange behaviour of the blower fan will result if you mix them up).

Pull off the connectors and unscrew the two screws.

You can now remove the module from the car.

Have an ohm-meter and check the resistance of the thermal fuse. It should be around a short circuit (less than 1 ohm) indicating that the fuse is intact.

If it is not, then short-circuit the fuse with a piece of wire and check whether the blower works with the switch in position 1 and 2. If it does not then remove the short-circuit and search further because the fault is somewhere else. Check the condition of the wire resistors and inspect for breaks etc.

If the fuse has broken then replace the fuse by a new one. I found it with the spare-parts shop for domestic electrical appliances.
Cut the old one out but leave some length of wire to attach the new connections too. Also be careful not to destroy it with the heat of the soldering iron. Ideally use a small pair of pointed pliers to grip the lead to keep the fuse cool when soldering the wires.

If the resistors themselves have blown you could make new resistors as follows.
 
Buy some resistance-wire of about 2 ohms a meter. Cut off 0.5 meter (the end to end resistance should be 1 ohm and wind it around a pencil or drill or something similar. You can now solder the replacement resistor in place using a heavy duty soldering iron. Note that the current through these resistors is pretty high (around 6,5 amps) so the wire should be thick enough to carry at least 8 amps.
 

Thanks to Ben in the Netherlands for this page

 

 

 

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