[Mgs] What is this part?

[INTOCARS at aol.com]

I have a 1969 MGB-GT that I am getting back into running condition.   There 
is an electrical part that I cannot identify and I need some help. It  is 
located in the engine compartment on the passenger side(left hand  drive) on the 
firewall.  It is about 5-inches below the windshield  washer reservoir(and 
heater fan motor), has one red and two green wires attached  and is about 2 1/2 
inches wide.  It might be a voltage stabilizer  ? 
Can you help?
Bob Dallas     
**************A Good Credit Score is 700 or Above. See yours in just 2 easy 
steps! 
(http://pr.atwola.com/promoclk/100000075x1218550342x1201216770/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=62%26bcd=fe
bemailfooterNO62)