Just bought a 1991 F-150 4.9L. Blower motor doesn't work. Need fuse diagram to check the fuse. Would appreciate the help.

 

Use your test light and check all the fuses

 

tested all fuses, ok. still not getting power to blower.

 

Dash switch or the resistor pack (under the hood, on the heater housing, rectangular plate, has a plug with several wires).
Also test fuses in the power distribution box under the hood near the battery.
Blower motor will be a bigger one - 20 or 30 amp I think.

 

I replaced blower motor resistor, still no power. Will check fuses in distribution box. THNKS.

 

Check the grey/yellow wire for power with the key on (it's @ the ignition harness in the column. This supplies your blower/accessories with power. If you have power there then check the HVAC selector connector on the back to test for power in and out.

EDIT:
You may also want to ensure that all of the vacuum lines on selector are in good shape, I believe that's how the system differentiates from OFF/Max/AC/Vent/Floor/Defrost. If the vac lines are bad or not getting vacuum it won't signal that it's been switched from off to a work setting. It may also be controlled with a guide wire, haven't ever dug into a 87-91, make sure that the wire is moving the selector that should be behind the glove box.

 

used test light on plug in to fan switch. no power. could the ignition switch be bad and not sending power to fan switch?

 

You basically need to track it back until you find power, it could be many things and you could end up replacing the entire system before you find the actual cause of the problem. You don't have power at the blower plug, so check the back of the climate control cluster. If still no power check the grey/yellow wire I mentioned earlier. If you have power at that wire then ignition switch isn't the problem. You just need to narrow down the point at which the power transfer stops.