[HO455]

Here is a copy from a post by Sneakysnake. It has the wiring diagram from a pickup A/C unit and I suspect the wiring on that and the Suburban rear are similar. The control switch sends power to the relay to control the med and low speeds and it should send power direct to the blower via the control relay. I don't believe that the relay should operate when high speed is selected thus the resistors are not part of the circuit at that time.
When the blower is turned from off to high the switch contacts from the high setting arc as the blower is not turning. Repeated over time this causes the high speed contact to fail. Having seen several units with toggle switches installed by POs probably means these switches are problematic and not available (or spendy)
Here is the link I copied the diagram from.

http://67-72chevytrucks.com/vboard/s...d.php?t=209480

To test your resistor use a meter set to ohms to check for continuity from tab #1 to #2 and then from tab #1 to #3 on the resistor. One ( the one with the larger coil) will have more resistance than the other. Then going from #2 to #3 will be total resistance of both checks (#1 to #2 and #1 to #3)

Good luck. If it continues to frustrate you try a post in the electric forum.