Before you go to the dealer (big $$$), examine the covers on both old and new relays. Most have a schematic of the terminal functions, based on the following conventions:

#30 is always the Input voltage to the Operating point or "Armature"
The Output (on your old one) should have *two* terminals:
#87, to the Hi-Lo relay on the left fender rail, and
#87a, to fuses 16 and 16 for the Parking lights

The relay coil (activating) terminals are:
#86, +12 volts
#85, Ground

The current-carrying capacity (i.e., 15A, 20A, etc.) should also be shown on the case.

Using the old relay's markings, you may find a much cheaper replacement at Radio Shack.

--
Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67