Wiring Appendix III Configuring the Relays, Wiring and Fuse Notes

The Sierra series of cars were fitted with a number of different designs of Relay and Fuse Boxes. There are no specific details in the later Haynes manual but the first volume ISBN 1 85010 312 7 has some very good diagrams (but not a lot of relevant information) on pages 188-190 and page 309. The fuses and relays were fitted by Ford on an " as required " basis. If they were not needed on that particular model, they were not fitted, hence all the spare sockets.

Essentially relays are electrically operated switches. They allow a small current to switch a bigger one, operate the horn, radiator fan, headlamps etc. and turn lights on/off. (flasher operation) They can also be used to switch multiple circuits or delay lights going off, as in interior lights etc. Older relays were electro/mechanical, whereas modern relays tend to be electronic. You will almost certainly need to fit at least two more relays. One for the horn and one for the electric coolant fan, as both these can pull quite large currents, especially if you fit twin air horns !! Once these are fitted and working I will add full details.

As far as the 2B is concerned we are only interested in three of these relays:-

a) The Flasher Relay, 30mm x 30mm x 50mm Ford Part No.19FL 012933 has 3 pins.

b) The Wiper Intermittent Relay, 30mm x 30mm x 50mm Ford Part No. 9FC 108 5pin (this is the only relay with a P terminal)

c) The 25mm x 25mm x 25mm relays have 4 pins, all numbered much the same, pins 85 and 86 operate the coil, whilst pin 30 is the input and pin 87 is the output.

There are two distinct pin layouts, Ford/BMW & Austin/Rover. 5 Pin versions have an additional pin 87a or 87-1.

Fitting the relays to the PWS wiring loom.

Plug the Flasher Relay (19FL 012933) into the only socket with 3 terminals fitted. Black/Yellow Pin 49+, 2 x Brown Pin 31-, White/Black Pin 49aL.(PWS colours)

Plug the Wiper Intermittent Relay (9FC 108) into the socket with 4 terminals fitted. 2 x Brown Pin 31, Black/Green Pin 54, Black/Yellow Pin 31b2, 2 x Brown/White Pin 31b1. The P pin is not used. (PWS Colours) See diagrams below:-

View of above FORD relays from the UNDERSIDE

Flasher (Indicator) Relay				Wiper Intermittent Relay
	49+	Black/Yellow			31	2 x Brown
	31-	2 x Brown			54	Black/Green ( Terminal P not used )
	49aL	White/Black			31b2	Black/Yellow
					31b1	2 x Brown/White

There are 2 more relay sockets, one with a Heavy White wire fitted at Pin 87, this is the Main Beam Relay, and a second with a Heavy Yellow wire fitted again at Pin 87, this is the Dipped Beam Relay. See the notes supplied by PWS on the green "Finding Your Way Sheet, Relay Holders" or read on. The lights on these circuits are fused with 20amp fuses, so we need at least a pair of 40amp relays. I fitted a pair of Ford 40amp relays. Solenoid pins are 85 & 86, and the the switched terminals are pins 30 and 87. (there is often a little circuit diagram on the side of the relay) At a pinch you can use the 5 pin relays as the centre pin (87a) is not used.

At a first glance the PWS notes are a bit confusing as they cover both the Ford/BMW and Austin/Rover relays as well as the two Sierra Column units, 83BG and 87BG. To avoid any confusion I have stuck with Ford relays, since it is basically a Ford car. The wiring details below are for Ford/BMW (c) relays and the 87BG column switch. The spare Brown earth wires fitted to the PWS loom when used in conjunction with the 87BG column switch are apparently not required. These should be cut right back to the relay terminal as soon as possible to avoid any possibility of shorts.

View of the FORD relays from the UNDERSIDE

Main Beam Relay				Dipped Beam Relay
	30	Heavy Red/White - From Supply			30	Heavy Red/Yellow - From Supply
	86	Thin Red/White			86	Thin Red/Yellow
	87	Heavy White - To Main Beam			87	Heavy Yellow- To Dipped Beam
	85	Thin Brown/White			85	Thin Brown/Yellow

Fuses.

The PWS loom is fitted with two banks of fuses, each bank has 4 pre-fitted fuses. The circuit protection details are given below:-
Mark the Banks 1 & 2 It is suggested you carry a copy of this diagram in the car in case of emergency. Carry a few spares, together with a spare relay.

A good guide to the fuse rating for typical automotive circuit applications is given on page 188 of the first Haynes manual. Blade pattern fuses have a
standard colour code. The rating in Amps is also marked on the fuse.

Cable Applications, 12volt systems only.

If in doubt note that Volts x Amps = Watts. (Ohms law) Thus a 60 watt lamp in a 12 volt system draws 5 amps. (12volts x 5amps = 60watts) Use at least 9/0.30 but 14/0.30 would give a lower voltage drop on a long cable run. Always use AT LEAST the same cable for earth purposes. Too small a cable causes fires. Note that a 6 volt system will draw twice the amps for a given load. If in doubt consult a qualified Auto Electrician. This applies particularly when fitting non standard items such as powerful Spotlights, 200watt Stereo's etc.

Battery state of charge as a function of Electrolyte Specific Gravity and/or Voltage.

A modern battery in good condition will give 2.4 volts per cell when fully charged. Any drop below 14.4 volts may indicate at least one cell down.

NB. It is no longer possible to measure specific gravity with modern sealed batteries or to measure individual cell voltages.

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© Colin Usher 2005