* Reverse Gear Switch (or related wiring): This is the most likely culprit. The reverse lights, and possibly other functions, are controlled by a switch on the transmission. If this switch is faulty or its wiring is damaged, it might be sending a faulty signal that interferes with the power steering system, perhaps grounding out a component or disrupting the power supply only when in reverse.
* Transmission-related pressure issue (less likely): While less probable, a pressure issue within the transmission itself, only apparent when in reverse, could theoretically interfere with a shared component or line used by the power steering pump. This is far less common.
* Power Steering Pump or Rack Issues (less likely, but possible): While less probable given the symptom is specific to reverse, a failing power steering pump or rack could have a weakness exacerbated by the additional load of reversing (often requiring more steering input). However, this would likely show symptoms beyond just reverse.
* Wiring harness issues: A short circuit or damaged wiring in the power steering system's harness could be causing this intermittent failure. A wire might be rubbing against a component that only comes into play when the transmission is in reverse.
Troubleshooting Steps:
1. Check the reverse lights: Do your reverse lights work correctly? If not, this strongly suggests a problem with the reverse gear switch or its wiring. This is the first place to start your diagnosis.
2. Inspect the Reverse Switch: Locate the reverse gear switch (often on the transmission itself). Visually inspect it for damage and check its wiring for any breaks, corrosion, or loose connections. If you're comfortable, you could test its continuity with a multimeter (be very careful working around the battery and transmission).
3. Check Power Steering Fluid: Ensure the power steering fluid level is correct and the fluid is clean. Low fluid or contaminated fluid can cause problems in any gear.
4. Professional Inspection: If you're not comfortable working on the car's electrical or transmission systems yourself, take it to a qualified mechanic. They'll have the proper tools and experience to diagnose the problem accurately. Explain the specific problem – power steering failure *only* in reverse.
The reverse gear switch is the most likely and easiest-to-check starting point. If that checks out okay, further investigation by a mechanic will be necessary to rule out the less-likely causes.
