Part 1 How To Test The Blower Motor Switch Ford 4 0l Test 1: checking continuity of the blower switch fan speeds. as stated in the previous section, the blower motor switch's job is to ‘bridge’ two separate contacts together. keeping this in mind, we're gonna' use a multimeter (in ohms mode) to check to see if two specific terminals are ‘bridged’ together. 1. disconnect the blower switch from its harness connector and turn the key to the on position (but no need to start the engine). note: all of the tests in this section are done on the blower switch's harness connector and not on the switch itself. the photo above shows the front view of the female metal terminals of the connector.
Part 1 How To Test The Blower Motor Switch Ford 4 0l On this ford f 150 the blower only worked on high even after i replaced the resistor. this is how i tested the blower resistor and switch. this will work on. If power is supplied to the blower motor through the speed switch and blower motor resistor: disconnect the electrical connector at the blower motor. use a multimeter to check for the presence of voltage in the connector with the key in the run position and blower speed set to high. you should see battery voltage (12 ). Step 3: replace the relay. with the key still in the off position, plug the relay back into the slot. turn on the key and try the blower. some relays may not activate until the car is running and have a built in delay so you may need to start the engine and wait a few seconds to see if your repair was successful. When you slide the mode switch away from the off position the blower motor switch is then energized. putting the blower switch on high bypasses the blower motor resistor so assuming your fuse is good, ac mode switch is good, blower motor speed switch is good and all wiring, you should get 12v at the blower motor connection.
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