Why would the heater and AC blower on a 1990 Toyota pickup not work at all speeds?

Answer 1

The blower motor itself is the most likely cause. It is located under the dash on the passenger side. The plug is usually white with a black and a blue wire. Remove the plug and run a test light between the 2 terminals, turn the key to "on"(engine not running) with the blower switch on in any position the light should turn on. If it does the blower is bad and can be replaced by taking out the 3 screws that hold it in. if the light does not light, the wires and fuse need to be checked. The fuse is labeled "heater" and is under the dash on the drivers side. If the blower works on high speed but does not work on one or more of the lower speeds-- the blower motor is OK. The problem lies in the resistor block, usually found attached to the air duct slightly downstream from the blower motor. Look for a 3 to 5 wire plug-in attached to the air duct. Remove the electrical plug carefully, then remove the 1 or 2 screws attaching the small flat plastic to the air duct. Gently remove the part-- if it has little coils of wire on it, you found the resistor. Treat it very carefully as the wires are brittle. Presuming you look at the coils (and see 1 or 2 with breaks in them) go get a replacement from a junkyard (cheap but used parts), auto parts store, or Toyota dealer. The Toyota dealer part will fit like a glove-- but take your heart medication before they tell you the price.