Lucas "ACR" model alternators have an integral voltage regulator mounted in the slip ring end bracket. The stator consists of star-connected, three phase windings on a ring end cover and drive end bracket. The rotor is either an eight or twelve pole type with the field windings connected to two face-type slip rings, and is supported in drive-end bracket by a ball bearing and in the end cover by needle roller bearings. One positive and one negative carbon brush ride against concentric brass slip rings. The heatsink-rectifier, terminal block assembly incorporate six silicon diodes, forming a full wave rectifier bridge circuit, and three diodes which supply current to the rotor windings.

NOTE: Up to a ten milliamp battery drain is normal, even with the ignition in the "OFF" position.

APPLICATION

Model		Type No.
Austin Marina		17 ACR
Jaguar
	XJ-6 Without Air Cond.	18 ACR
	XJ-6 With Air Cond.	20 ACR
	XJ-12	20 ACR
MG (All Models)		16 ACR
Triumph
	Spiff ire Mark IV	16 ACR
	TR-6	18 ACR

SPECIFICATIONS

Nominal Output

Alternator

Amps @ RPM

⁽¹⁾ Voltage

16 ACR

34 @ 6000

17 ACR

36 @ 6000

18 ACR

45 @ 6000

20 ACR

66 @ 6000

⁽¹⁾	Charging Voltage, 14V.

RESISTANCE VALUES (OHMS)

Alternator

Stator Coil

Rotor Coil

16 ACR

0.138

⁽¹⁾

17 ACR

0.133

4.2

18 ACR

0.092 ⁽²⁾

3.2

20 ACR

0.180-0.200

3.6

⁽¹⁾	4.3 ohms with pink windings, 3.3 ohms with purple windings.

⁽²⁾

±5%.

Fig 1: Lucas Intergral Regulator Alternator ("ACR" Type)

Courtesy of NOT AVAILABLE

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Alternators - LUCAS: Description

Use the Manual With the Right Hardware

When to See a Mechanic