Home / DTC / C1735 — Compressor Relay Short to Battery

C1735 — Compressor Relay Short to Battery

Detailed page for trouble code C1735.

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Code

C1735

HUMMER C — Chassis

Compressor Relay Short to Battery

Brand: HUMMER
Views: UK: 10 EN: 12 RU: 14
AI status
Completed
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Completed 100%
Page language: EN

Causes

  • Shorted relay control wire to constant battery feed (chafed harness, pin contact to power wire)
  • Stuck or welded relay contacts (relay failed closed)
  • Faulty compressor drawing power back into control circuit
  • Faulty relay socket or connector with melted insulation causing shorts
  • Corroded or damaged connectors (water intrusion)
  • Aftermarket equipment or recent wiring repairs incorrectly tied to constant battery

Symptoms

  • Compressor runs continuously or at unintended times
  • Battery drain / discharged battery after vehicle sit
  • Fuse for compressor circuit repeatedly blows
  • Air suspension (or related system) will not maintain proper ride height or cycles incorrectly
  • Service message or DTC-related warning on dash
  • Intermittent or no compressor operation if the circuit is protected by a blown fuse

What to check

  • Retrieve freeze frame and active/confirmed status with a scan tool; verify C1735 is current and note conditions when set
  • Visual inspection of compressor relay, relay socket, wiring harness and connector for melted insulation, corrosion, or pin damage
  • Check fuses for the compressor circuit and any related power distribution fuses
  • Remove compressor relay and inspect relay contacts; with the relay removed, check if the compressor or circuit still has battery feed
  • With key off, measure continuity between relay control circuit and battery positive to confirm short (expect open/no continuity when not powered)
  • Command compressor on/off with a scan tool and monitor voltage on the relay control terminal and compressor power terminal

Signal parameters

  • Relay control signal: should be ~0 V (ground or low) when not commanded and near battery voltage (~12 V) only when the control module commands the relay ON
  • Relay coil resistance: typically low ohms (tens to low hundreds of ohms). Consult vehicle service manual for exact value
  • Compressor power circuit: when commanded ON, expect battery voltage at the compressor power terminal and a significant current draw (several amps to tens of amps depending on compressor)
  • If a short to battery exists, relay control circuit will read near battery voltage even with command OFF

Diagnostic algorithm

  1. Safety: Park vehicle on level surface, chock wheels, disable system as required, and disconnect battery before performing direct wiring repairs. Use PPE and insulated tools.
  2. Verify code: Connect a scan tool, confirm C1735, note whether fault is active or history, and record any related codes.
  3. Visual inspection: Inspect relay, socket, compressor connector, and wiring harness routing (look for chafing, pinched wires, melted insulation, corrosion, or water ingress).
  4. Relay test: Remove the compressor relay. With ignition ON, check for battery voltage at the relay power supply terminal and check the relay control terminal for unintended battery voltage. If control terminal is hot with relay removed, suspect wiring short to battery or module fault.
  5. Isolate circuit: Disconnect the compressor motor connector. If the short or voltage persists at the relay control circuit with compressor disconnected, the fault is in wiring or the module, not the compressor motor.
  6. Measure continuity: With key off, measure continuity between the relay control circuit and battery positive. If there is continuity, trace the harness to find the short (use back-probing and connector separation to locate the section with continuity).
  7. Current test: If safe and required, command the compressor ON with a scan tool and measure current draw to check for abnormal load (compare to service spec). Excessive current may indicate a compressor motor fault.
  8. Inspect module: If wiring and relay are good, suspect control module driver fault. Check for technical service bulletins related to C1735 for the vehicle.
  9. Repair: Repair or replace damaged wiring, connectors, relay, or compressor as indicated by tests. Replace relay socket if contacts are damaged. Re-install components and secure harnesses away from heat and moving parts.
  10. Verify: Clear codes, reconnect battery, command compressor several times and road-test / cycle vehicle to confirm no return of C1735 and normal system operation.

Likely causes

  • Damaged/chafed control wire contacting a battery feed or fused power circuit
  • Failed relay that is stuck closed
  • Relay socket/connector shorted to battery power
  • Compressor internal short or stuck motor causing unusual currents
  • Incorrectly modified wiring (aftermarket accessories)

Fault status

⚠️ Status
Compressor relay control circuit detected battery voltage when it should be off (short to battery). System may run compressor unexpectedly or blow fuses. Further wiring and component inspection required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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Code

C1735

Other C — Chassis

Air Suspension LR Corner Up Timeout

Brand: Other
Views: UK: 15 EN: 22 RU: 23
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Shorted relay control wire to constant battery feed (chafed harness, pin contact to power wire)
  • Stuck or welded relay contacts (relay failed closed)
  • Faulty compressor drawing power back into control circuit
  • Faulty relay socket or connector with melted insulation causing shorts
  • Corroded or damaged connectors (water intrusion)
  • Aftermarket equipment or recent wiring repairs incorrectly tied to constant battery

Symptoms

  • Compressor runs continuously or at unintended times
  • Battery drain / discharged battery after vehicle sit
  • Fuse for compressor circuit repeatedly blows
  • Air suspension (or related system) will not maintain proper ride height or cycles incorrectly
  • Service message or DTC-related warning on dash
  • Intermittent or no compressor operation if the circuit is protected by a blown fuse

What to check

  • Retrieve freeze frame and active/confirmed status with a scan tool; verify C1735 is current and note conditions when set
  • Visual inspection of compressor relay, relay socket, wiring harness and connector for melted insulation, corrosion, or pin damage
  • Check fuses for the compressor circuit and any related power distribution fuses
  • Remove compressor relay and inspect relay contacts; with the relay removed, check if the compressor or circuit still has battery feed
  • With key off, measure continuity between relay control circuit and battery positive to confirm short (expect open/no continuity when not powered)
  • Command compressor on/off with a scan tool and monitor voltage on the relay control terminal and compressor power terminal

Signal parameters

  • Relay control signal: should be ~0 V (ground or low) when not commanded and near battery voltage (~12 V) only when the control module commands the relay ON
  • Relay coil resistance: typically low ohms (tens to low hundreds of ohms). Consult vehicle service manual for exact value
  • Compressor power circuit: when commanded ON, expect battery voltage at the compressor power terminal and a significant current draw (several amps to tens of amps depending on compressor)
  • If a short to battery exists, relay control circuit will read near battery voltage even with command OFF

Diagnostic algorithm

  1. Safety: Park vehicle on level surface, chock wheels, disable system as required, and disconnect battery before performing direct wiring repairs. Use PPE and insulated tools.
  2. Verify code: Connect a scan tool, confirm C1735, note whether fault is active or history, and record any related codes.
  3. Visual inspection: Inspect relay, socket, compressor connector, and wiring harness routing (look for chafing, pinched wires, melted insulation, corrosion, or water ingress).
  4. Relay test: Remove the compressor relay. With ignition ON, check for battery voltage at the relay power supply terminal and check the relay control terminal for unintended battery voltage. If control terminal is hot with relay removed, suspect wiring short to battery or module fault.
  5. Isolate circuit: Disconnect the compressor motor connector. If the short or voltage persists at the relay control circuit with compressor disconnected, the fault is in wiring or the module, not the compressor motor.
  6. Measure continuity: With key off, measure continuity between the relay control circuit and battery positive. If there is continuity, trace the harness to find the short (use back-probing and connector separation to locate the section with continuity).
  7. Current test: If safe and required, command the compressor ON with a scan tool and measure current draw to check for abnormal load (compare to service spec). Excessive current may indicate a compressor motor fault.
  8. Inspect module: If wiring and relay are good, suspect control module driver fault. Check for technical service bulletins related to C1735 for the vehicle.
  9. Repair: Repair or replace damaged wiring, connectors, relay, or compressor as indicated by tests. Replace relay socket if contacts are damaged. Re-install components and secure harnesses away from heat and moving parts.
  10. Verify: Clear codes, reconnect battery, command compressor several times and road-test / cycle vehicle to confirm no return of C1735 and normal system operation.

Likely causes

  • Damaged/chafed control wire contacting a battery feed or fused power circuit
  • Failed relay that is stuck closed
  • Relay socket/connector shorted to battery power
  • Compressor internal short or stuck motor causing unusual currents
  • Incorrectly modified wiring (aftermarket accessories)

Fault status

⚠️ Status
Compressor relay control circuit detected battery voltage when it should be off (short to battery). System may run compressor unexpectedly or blow fuses. Further wiring and component inspection required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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