'92 Amigo, S model...
The AC fan will only work on high(4) when moved
to 4 or 3 the fan doesn't work.
Any help/thoughts with a solution..?
Is it the switch, a relay and which ever it is...do you FIX it or REPLACE it?
If fix...HOW? If REPLACE...from where?
Normally, when a fan motor works only on high, that indicates the rheostat/ resistor assembly is burned. The high speed is on another circuit thus allowing it operate independently of the lower speeds. you should be able to determine its location using this link. http://www.myisuzuparts.com/
i don't know how to draw a circuit on the pc but it would look like this
battery to ---high speed>resistor>resistor>resistor in series , the blower would be switched to the different connectors for different speeds
at the end of the high speed above full 12v to blower motor ,as it is switched down the resistor chain, the voltage is dropped in the resistors , so at the end the voltage is min , so less voltage to blower motor
that is what happens to blower motor switched resistors , they do not have a high enough wattage to handle the voltage drop ( which is higher if the motor fan is dirty , takes more current to operate , so more voltage drop)
this may sound like a bounch of bs, but it is a reason i always run the blower at high speed , then the resistors are not used and the blower fan should stay cleaner because of the high speed.