Heater Motor on High Speed Only

Asked by Jan 08, 2015 at 12:27 PM about the 2003 Mercury Grand Marquis LS Premium

Question type: Maintenance & Repair

Earlier the resistor was changed due to no fan at all worked for 4 months now fan motor blowing on high only. Could it be the switch or resistor or motor not sure can you help.

5 Answers

10,590

Usually if the fan only works on high, it is the resistor.

3 out of 3 people think this is helpful.
30

has new resistor still only works on high

2 out of 2 people think this is helpful.
30

has new resistor still only works on high fan

1 out of 1 people think this is helpful.
10,590

The most common cause here is a bad resistor, but since you are confident that isn't the problem, it is likely the switch. However, I did have a situation once in a dodge caravan. The fan motor itself was causing a voltage problem and ruining the resistors.

1 out of 1 people think this is helpful.
10,590

You can use a simple test light. Unplug the wire to the resistor. Should have a 5 or 6 prong plug. Turn the key to the run position. Probe each pin with the light as you change the setting on the switch. If it lights up at each setting that means it is working and the resistor is bad. If not, then the switch. If the resistor is new and not working, or if there are any melted connections, then the fan motor is the likely culprit.

2 out of 2 people think this is helpful.

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