Help.. I am in no way a Gearhead and I'm learning as I go. All of a sudden my high speed AC fan is not working. It works fine on low and medium but when I switch it to high I get no air at all. I did some internet research and replaced the high speed fan relay under the hood and verified that my AC heater control switch is also working fine. Any ideas?
When operating the blower on the LO/MED1/MED2 settings, power to it is supplied from the fuse labeled HTR AC which is located in the normal fuse block under the dash. It gets to the blower via the resistor stack
However, when the HI setting is selected, the power to the blower motor windings is direct from the battery. Moving the fan speed controller to HI only actuates the relay's coil. Then when relay pulls in, the blower gets full battery voltage.
In order for that HI SPD circuit to work, you need a power supply from the firewall junction block to the fan relay (it gets there on a fat red wire)also the relay's coil must be operating and properly grounded. Since you installed a new relay, you can probably eliminate the coil.
That leaves the main power feed on the red wire and the ground lead for the coil. When in any other speed than HI the coil is de-energized and in the default position. All speed regulation occurs in the dash switch and resistor stack.
There is 30 amp inline fuse spliced into the main supply - probably right near the junction block. The wiring dwgs show it located where the red lead changes to an orange lead - that orange one is what ultimately connects to the relay.
Fuse okay and power getting to the relay - check the ground lead.
