A thermal sleeve and method for protecting a temperature sensitive electronic member against exposure to heat. The thermal sleeve includes a tubular wall with an inner surface bounding an inner cavity extending along a central longitudinal axis between open opposite ends and a reflective outer surface. The thermal sleeve includes a positioning member constructed of a separate piece of material from the tubular wall, with an annular portion attached to the tubular wall and at least one resilient finger extending radially inwardly from the annular portion. The at least one finger extends radially inwardly along a plane from the fixed end along an arcuate path to a free end configured for abutment with a wiring harness attached to the temperature sensitive electronic member. The free end of the finger is radially expandable along the plane toward the annular portion to automatically adjust to an outer envelop of said wiring harness.