How to find why there insn't power to the blower.

So blower has POWER at plug? Is ground good too?

Since there is no power to the blower, you need to trace the power supply back until you find where power is lost.

First check the blower motor activity on HIGH. If it only runs on HIGH the blower motor resistor is bad.

If it still does not work, check the following:

Check fuses #8 (7.5A) and #17 (30A). They supply power to the blower motor relay. If they are good, remove the blower motor relay and use a testlight to check fot power at the relay socket (two of the recepticals in the socket should have batery voltage---the other two should not).
If voltage is there, switch the relay with an identical one (should be at least one more in the same fuse box). If the blower now works, replace the relay.

If not, check for voltage at the blower motor YEL/BLK wire with the key on and the blower speed set on HIGH.
I no voltage check for a short in the YEL/BLK wire.

If blower still doesn't work check the ground circuit between the blower and the blower fan switch. To do this use an ohmmeter and with the ignition OFF place on ohmmeter lead into the blower motor's BLU/RED wire and the other lead on a good ground (bolt or bare metal). Reading should be 0.0 If so the ground is good.
Get back to me on this.