Relays and the Voltage Regulator

Figure 1

Bonnet tape

Direction Indicator Flasher Unit.

The original direction flasher relays fitted to Morgans in the early seventies were Lucas type 8FL units. They are designed to handle 2 x 12V x 21W indicator lamp bulbs + 6W (for side flashers) and a 2W warning lamp bulb. If you are restoring a Morgan manufactured between 1970 and 1995, it will most probably have the same unit fitted. Morgan originally mounted them by fixing a three blade Lucar connector socket to the wooden scuttle top rail as shown in Figure 1. Replacement is quick and easy, as the old relay is simply unplugged and replaced.

A green wire from the ignition auxiliaries fuse supplies power to terminal B. A light green wire with a brown tracer connects the indicator switch to terminal L

Hazard Warning Flasher Unit.

The original hazard warning flasher relays fitted to Morgans in the early seventies were Lucas type 9FL units. They are designed to handle 4 x 12V x 21W indicator lamp bulbs, plus 2 x 5W warning lamp bulbs. The hazard warning flasher unit is mounted on a three blade Lucar connector socket fixed to the wooden scuttle top rail.

A brown wire from an independentin line fuse supplies power to terminal B. The fuse is wired back to the battery via the ammeter. The hazard warning flasher has its own fuse so that it still works when the ignition is switched off, even if the constant current auxiliary fuse has blown. The fuse can be found close to the hazard flasher unit behind the dash board. A green wire with a light green tracer connects the hazard warning light to terminal P. A light green wire with a pink tracer connects the hazard warning switch to terminal L.

Instrument Voltage Regulator Unit.

The original Smiths instrument voltage regulator was mounted on the bulkhead. When purchasing a replacement, check it is suitable for negative earth instruments and check with a Morgan agent to identify the one required for your particular car. The water temperature gauge, temperature sensor, fuel gauge, and fuel tank unit, rely upon the voltage regulator to supply the correct voltage and iron out variations in output from the generator. The old regulators were set to supply 10 volts to the instruments. Inside their casing, a bimetallic strip, heats up and bends when a voltage of ten volts passes through it. This in turn opens breaker contacts. When the contacts are open the strip rapidly cools and the contacts close and the cycle continues. The instruments are damped so that fluctuations are not noticeable.

A green wire from the constant current auxiliary fuse feeds power to terminal B. A light green wire connects terminal I to the fuel and water gauges. These gauges are respectively connected to the fuel tank unit and engine temperature sensor by green wires with black tracers.

The Smiths impulse tachometer, the speedometer, ammeter and the oil pressure gauge are independent of the voltage regulator.

IMPORTANT: An old BIMETALIC STRIP REGULATOR MUST BE MOUNTED THE CORRECT WAY UP and the fixing bracket must be earthed. Mount it on the bulkhead, DO NOT MOUNT IT ON THE WOODEN FRAME and ensure a little paint is scraped away around the fixing bolt. The original regulators are marked with an arrow and are labeled " TOP " to indicate the correct orientation when fitting them. The wiring connections to the instrument regulator and flasher units are shown in Figure 2. Later regulators utilised a transistor controlled by a zener diode with a cut off voltage of ten volts. Nowadays solid state regulators are used. If you fit either of the last two types, orientation should not be an issue.

Figure 2

Bonnet tape

The flasher relays are usually reliable, but if they fail, replacements are still readily available on the internet. If flasher faults occur, check the indicator bulbs and the condition of the bulb housing before replacing the relay. Also look for faulty wiring. Any fault which increases resistance in the flasher circuit, may lead to a relay malfunctioning. If the current is not high enough, the bimetallic strip may not break contact and indicator lamps can continuously glow, or not illuminate at all. I once had water creep inside a direction flasher relay when the scuttle leaked. When I signaled to turn, the indicator lamps glowed faintly, but refused to flash. I assume the bimetal strip inside the unit stayed too cool to snap in and out, or maybe the contact gap was shorted out by the water. Pure water does not conduct electricity, but I assume impurities in rain water may allow it to do so. It is possible the unit had leaked for a while and and allowed the water to gain enough ions from corrosion products to allow conduction. Whatever, the main point is to ensure the relays are kept dry. Maintaining a watertight seal on the indicator lamp housings is also important

The bonnet is insulated from the scuttle with bonnet tape. The tape is held in position with steel pins, which puncture the steel scuttle and ash frame. In time, some pins can work loose and allow leaks to develop. Rebuilding a Morgan offers the opportunity to use a good quality sealant between the frame and panels. Not only will this protect wiring and components inside the car, but it will help protect the panels rusting from the inside out. The wooden frame will also benefit.

Back to the top