On the '79 DHC there are three relays on the right and one on the left side of the fuses. Also a Petronix unit and a flasher unit. By process of elimination the bottom ones are headlights. The right center is the starter so the upper right is probably the horn. If you have a two on the left side then you have a choice of two for the horn. I have no idea what the third would be unless you have AC.
Before you replace relays check to make sure that each wire inside of the connector is making contact with the relay. The spade connectors at the end of the wires can get pushed back when installing the relay. I found this happening on two relays, the starter and the headlight. In the case of the starter I was getting voltage but not enough amps because of the weak connection. It is very hard to see if the wire is correct because of the shortness of the wire lead and the difficulty of working through the glove box. Look at each wire and if you see any part of the top of the spade connector outside of the plastic connector then connect it to the relay and with a pair of needle nose pliers push the wire back into the plastic connector. This is not easy but it works.
[img][IMG]http://i615.photobucket.com/albums/tt234/nickmi/TR7%201975/Yellow.jpg[/img]
nick
'79 TR7 DHC
'76 TR7 FHC
