Vauxhall Astra Astra H 1.7 CDTi 100bhp — Alternator Failure
The alternator on the 1.7 CDTi Astra is a notorious weak point. It fails without much warning, draining the battery and leaving the car stranded.
Severity
CriticalDIY Difficulty
Moderate
Est. Cost
£250–£400
OBD Codes
None
Electrics
Typical layout and location for the Electrics assembly.
Symptoms
- Battery warning light on dash
- Whining noise from engine bay
- Power steering suddenly goes heavy (electric pump loses power)
- Dashboard lights dimming or flickering
Root Cause
The diode pack inside the Denso/Bosch alternator overheats and burns out. Oil leaks from the vacuum pump (mounted on the alternator in some versions) accelerate failure.
How To Fix
- Test charging voltage across battery with engine running (should be 13.8V - 14.4V, if <12.5V alternator has failed)
- Replace alternator
- Ensure battery is fully charged using a wall charger before starting with new alternator
- Cost: £250-400
Estimated Repair Costs
| Repair Option | Est. Cost (GBP) |
|---|---|
| DIY (parts only) | £100–£160 |
| Independent Garage | £250–£400 |
| Main Dealership | £400–£640 |
Other Faults on This Variant
EGR Valve Failure
ModerateThe Isuzu-sourced Z17DTH and Z17DTJ engines in the Astra H have a well-documented EGR valve failure. Carbon deposits cause the valve to stick, resulting in power loss and increased emissions.
DPF Blockage
ModerateDPF-equipped Astra H 1.7 CDTi models (post-2007) suffer from the same DPF blockage issues as most diesel Vauxhalls of this era. Urban use is the root cause.
Dual Mass Flywheel Failure
ModerateDMF wear on the Astra H 1.7 CDTi is a high-mileage inevitability. The flywheel's internal dampers lose effectiveness, causing vibration and judder that makes the car unpleasant to drive.
Disclaimer: Repair cost estimates are indicative and based on community data. Always get a quote from a qualified mechanic before proceeding with any repair.