Bert,
Don't know for sure what/where/how you bought what you did, but according
to the net it is a glow plug relay.
http://www.ebay.com/itm/Diesel-Glow-Plug-Relay-BOSCH-0-332-002-156-/170647516431
example schematic here.
http://www.fordmuscle.com/archives/2003/02/electricfan/index.php
30 -- Aux Battery +
87 -- Starting battery +
85 (or 86) --- GROUND
86 (or 85) --- Attach to the blue wire that goes to the generator
warning lamp from the voltage regulator.
The blue wire goes from ground to 12+V when the generator spins up and
starts charging. It can be used for
