MGBGTV8 Halogen headlight conversion with twin relays
Following our recent V8NOTE572 on installing an H4 Halogen headlamp upgrade to replace the original sealed beam lights, a further upgrade involving installing twin relays to remove the heavy electrical load on the ageing main lighting switch and the stalk dip/main beam switch was highlighted as a very worthwhile but subtle upgrade. Here Peter Spurrs contributes a note describing his installation of the relays using individual parts purchased from an auto electrical supplier.

H4 Halogen headlight upgrade for an MGBGTV8 - see V8NOTE572

What bulbs are suitable for a headlight upgrade? V8NOTE578

Relays - what are they and what do they do? V8NOTE579

What does the headlight relays & wiring kit from Moss Europe look like? Note

Wiring diagram & diagram (Bentley)
Posted: 200220

Halogen headlights
The photo above compares the main beams with Halogen bulbs and the original sealed beam units. The offside headlight is a Cibié H4 unit with an Osram Nightbreaker Laser bulb. The nearside has the original sealed beam light. The improvement is obvious. The steps necessary for removing and replacing the headlights are covered on page 40 of the MGBGTV8 Driver’s Handbook. Using a replacement H4 Halogen headlight unit is described in V8NOTE572.

Installing and testing the twin relays
In V8NOTE577 Peter describes the steps necessary for installing and testing twin relays and he also provides a wiring diagram showing where and how to make the necessary connections for the relays in the existing wiring loom. See the full note: V8NOTE577

The advisability of fitting relays to the main and dipped beam headlight circuits is covered in detail elsewhere. It boils down to an electrical load of 10 amps being fed through the very small contacts on the indicator/dip stalk switch. Using modern relays to switch the load on and off avoids possible damage to the ageing switches. Approaching 50 years old in most MGBV8s, protecting that switch using the relays is a sensible upgrade.

Third party ready made relay kits are available - Moss Europe has twin relays all pre-wired for installation at £36 (February 2020). Peter went for another option which is to buy the relays and to wire them oneself. At the time of writing, a six-pack of five terminal fused relays was available for £12 on the internet. Two are used for the installation and the others can be carried as spares in case of failure.
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