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Your foglight wiring •
Page 23
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roblems mode clear
THE SOCIETY of Motor Manufacturers and Traders has drawn up a set of recommendations designed to help operators of articulated vehicles meet the new rear fog-light regulations which are introduced on November 1.
The SMMT fears that some operators may experience problems in connecting existing tractor-trailer connections or new ones where different standards are involved. An illustrated guide to the different types of connections is to be available from the SMMT later in the year, but in the meantime we reproduce the basic recommendations.
For 24V systems on new tractors and trailers, an ISO 1185 normal connector should be used, and for connecting rear fog-lamps, a supplementary connector ISO 3731.
In the case of new tractors and trailers with 12V systems, use connectors to BS:AU:149 or ISO 1724, which are fully interchangeable. Both these standards are being updated to make sure the spare number 2 contact into the rear foglamp contact. • For matching old and new tractors and trailers, the recommendations are rather more complex.
With both 12V and 24V tractors, current UL practice is to fit a coiled cable from a junction box on the gantry or cab bridge terminating in a plug. It is recommended that new 12V tractors be fitted with a fixed socket to ISO Specification 1724 or to BS:AU:149 and that 24V tractors should be equipped with two fixed sockets to ISO 1185 and ISO 3731.
If the new ISO-wired tractor • is to be coupled to an existing EE-4L "SMMT" trailer, the "normal" plug and socket will mate and all services wit be correctly connected, but with certain provisos. First, that the operator removes any unwanted bridge between contacts 1 and 2 that may be fitted to the EE-4L socket, and second, that the tractor manufacturer approves of the right-hand tail-lamp fuse on the tractor carrying the trailer• tail-lamp load.
For existing 12V (EE-4L) tractors, a BS:AU:149 socket (ISO 1724) should be fitted, wired where appropriate, in parallel with the existing EE4L plug, and an interlink cable used between the new socket and the trailer. This arrangement still permits the existing EE-4L coiled cable to be used with a 12V EE-4L trailer.
As far as existing 24V (EE4L) tractors are concerned the recommendation is to fit an ISO 1185 socket wired, as described above, in parallel with the existing EE-4L plug, and also an interlink cable used between the new socket and the new trailer. The existing EE-4L cable can still be used with a 24V EE-4L trailer.
New 24V trailers carrying rear fog-lamps will have two fixed sockets, a normal and a supplementary. With regard to connector identification, it is recommended that, to reduce the risk of possible mismatch, 24V EE-4L connectors should be marked indelibly in green, while reworked 12V 5E-4L connectors should be indelibly marked in yellow.