Here is the schematic ( \/ \/ CLICK \/ \/ ): Manual HVAC Blower Motor Schematic
From your symptoms, we know that the wiring to/from pins 87A & 30 on the blower motor relay are working fine. What we do not know is if there is a proper ground to the switching coil (pin 85), switching signal power (pin 86) and then the input power on pin 87 that comes from the HVAC fuse in the underhood fuse box (which is not to be confused with the HVAC fuse in the instrument panel fuse box that powers the fan through the blower motor resistor).
BTW, I would only keep that Chilton's manual around if you need a wheel chock or table leg shim. That's about all they are good for. They are way too generic in terms of information to be helpful. I like AllDataDIY.com for the money; 5yr subscription is $50 for the first vehicle, $35 for each additional vehicle.
Thank you again. First. I agree about Chilton's. Completely a let down buzz kill. Especially with Internet. It has slight uses but rarely much to me. YouTube does better on all fronts.
In the three lowest fan settings the power for the blower motor runs through various legs of the resistor network (3 resistors) to vary the current to the motor. In those three positions the power leaves the resistor and passes through the relay power contacts (87a and 30) that are connected when the relay is not energized. As Swartlink says in this mode power is supplied through HVAC fuse 9/20A in the I/P fuse block on the left side of the dash. When you switch to position 4 the power routing for the blower motor changes. It does not use the resistor network and now the power comes from a different fuse (HVAC fuse 30A) in the underhood fuse block. Now you depend on the relay to energize to route this power to the blower motor whereas in the other cases the relay routes power while at rest. In all cases power exits the relay on pin 30 so anything that puts fused power on 30 will make the motor run on high.
Check the underhood 30A HVAC fuse and if good, check for power at pin 87 (not 87a). if you have power there then check for power at pin 86 when the control is in position 4. If thats good then check for a good ground at pin 85.
Please read the explanation and perform the testing that I outlined in post #16. Also make sure that you used the proper type of relay that has both 87 and 87a contacts as that DPST configuration is not used everywhere.
Verify power at the upstream pin of the 30A underhood fuse block and if that's good then your problem is in the orange wire that runs from that fuse to pin 87 or the connector under the underhood fuse block that routes that wire.
09-26-2019, 04:54 AM
