Ok here goes:
-the car is an '87 IROC which originally had an LG4
-a carbed zz4 was put in and most of the electronics were either hacked or disconnected
-the current engine we're trying to get to work properly is a '92 LO3 (TBI) from an RS
-We're using the dash harness from the IROC
-We're using the engine harness from the RS

-Almost everything matches up enough to get the car on its way (it needs to run to be sold)
-We've so far encountered a couple problems where wires fit in a harness but their function doesn't match that of the wire on the other side of the harness.

-The current one that's bugging us is the blower motor circuit
-It is popping every time we put a fuse in under the dash and set the car to ignition.
The motor is grounded properly and the power to the blower is connected to the correct place for a manual heating system as described in the '88 shop manual we are using

-We've been through the schematic a couple times and found other things wrong and fixed them, but now I'm just wondering:

DOES ANYONE HAVE ANY IDEAS ON WHAT'S CAUSING THIS FUSE TO BLOW?

-Any thoughts would be appreciated If you need more info I'll be glad to supply what I can. Thanks guys

 

ttt

 

Are you sure the blower motor itself isn't locked up or bad ?
If all the other wiring is correct to the best of your knowledge, the motor or the blower speed resistor would be the next suspicious culprit on my list. But, that's just me.. I could easily be wrong.