911 (Classic Air-Cooled)

1964-1989 / Coupe / Targa / Cabriolet / Germany

All 911 (Classic Air-Cooled) problems All workshop issues

Critical Electrical

Alternator and Charging Issues

Symptoms

Low charging voltage, flat battery, dim lights. The red generator/alternator light stays on or flickers.

Cause

The alternator on air-cooled 911s is engine-mounted and runs at high temperature. The internal regulator and brushes wear, reducing output. The serpentine belt (or V-belt on older cars) that drives the alternator also drives the cooling fan, if the belt snaps, you lose both charging and engine cooling simultaneously.

Fix

Alternator rebuild or replacement: $300-$600.

Belt replacement: $50-$100.

Always carry a spare belt, a broken belt means immediate overheating.

Cost mentioned in fix

$300-$600$50-$100

Know something we don't?

Owned a Porsche 911 (Classic Air-Cooled)? Share your experience with this issue. What worked, what didn't, costs, tips. Help the community.

Submit an update

// More 911 (Classic Air-Cooled) problems

Other known issues

Critical Electrical

CDI Ignition Module Failure (1969-1977)

Engine cuts out without warning, intermittent misfiring, no-start condition. The Capacitive Discharge Ignition module fails.

Minor Engine

Cam Chain Tensioner Failure (3.2 Carrera)

The cam chain tensioner fails, allowing the duplex timing chain to go slack. The chain skips teeth on the sprockets, the camshaft timing shifts, and the valves collide with the pistons. The result is catastrophic, bent valves, damaged pistons, and potentially a cracked cylinder head.

Common Engine

Valve Guide Wear

Blue smoke from the exhaust on start-up (oil pooled on valve heads drains into the combustion chamber) and on the overrun (oil drawn past the guides by manifold vacuum). Increased oil consumption.

Critical Engine

Oil Leaks, The Usual Suspects

Oil residue on every surface of the engine. Active dripping in the garage.

Critical Engine

2.7-Litre CIS Engine, Nikasil Cylinder Scoring

Increased oil consumption, loss of compression, rough running, and blue exhaust smoke. The engine gradually loses power and efficiency.

Common Engine

Thermal Reactor Exhaust Damage (1975-1977)

Exhaust valve recession, burnt valves, cracked exhaust studs. The thermal reactor runs extremely hot to burn unburned hydrocarbons.

View all 13 911 (Classic Air-Cooled) problems