Here's a summary and bullet point breakdown of the call between Eric from Pennsylvania and Ron Ananian on The Car Doctor radio show from April 26, 2025:

🔧 Caller Issue:

• Vehicle: 2013 Chevrolet Suburban LTZ

• Mileage: 230,000 miles

• Engine: Multiple crate engine replacements (current one is 3rd crate engine)

• Main Symptom:

  • Voltage drops from ~14V to 10V during driving, especially on long trips.

  • AC compressor shuts off when voltage drops.

  • Vehicle eventually enters limp mode.

  • Turning headlights on brings voltage back to normal (~14V).

🛠️ Previous Work Done:

• New Alternator and Battery: Both replaced with OEM GM parts (twice).

• Added Ground Wires: Installed by an electrical specialist.

• AFM (Active Fuel Management) Disabled.

• No Aftermarket Parts: Only modification is AFM delete.

🧠 Diagnostic Observations & Suggestions (Ron Ananian):

• Key Question: Is this a headlight-specific circuit issue or a general electrical load problem?

• Blower Fan Test:

  • Blower fan doesn’t resolve the issue like headlights do, suggesting it’s circuit-specific, not general load.

• Electrical Theory:

  • Turning headlights on might bypass GM’s energy-saving mode, stabilizing voltage.

  • Could be a module communication/network issue—one module dropping out could cause system-wide failure.

  • Ron compares it to computers on a network: one fails, the rest follow.

🧪 Further Diagnostic Path Ron Suggests:

• Scan Tool Needed: Check for module communication failures during voltage drop.

• Cluster/Oil Pressure Warning:

  • Oil pressure reads low on dash but is fine on manual gauge.

  • Possible faulty cluster or wiring issue, possibly affecting system behavior.

• Check Bulkhead Connector: Wiring harness going through firewall may be suspect.

• Evaluate What’s Working: Don’t just chase bad parts—establish what’s good (e.g., fuel trims, throttle position, vacuum).

• Disconnect AC Compressor Electrically:

  • See if the issue still occurs with AC unplugged to isolate AC clutch as a cause.

🔁 Next Steps for Eric:

• Determine if AC compressor clutch is affecting the system or just coincidentally shutting off.

• Investigate further with his technician using Ron’s suggestions.

• Call back with updates for continued guidance.

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