Car Regulator

Any vehicle with an alternator needs a car regulator to prevent the voltage moving through the system exceeding safety levels. The car regulator is in essence a voltage regulator that allows enough voltage to charge the battery but not so much as to blow out circuits or lights.
If you need to replace this part then quality

car regulators

for any car are widely available. The likelihood is that there will be a specific car regulator for your make and model of vehicle.
 

Car Relay

The car relay is an electromagnetic switch, which clicks on or off when power is applied to a coil so that a power wire to a particular component or function is either connected or disconnected.

Car relays

are used in a number of electrically controlled systems including certain aspects of lighting and car alarms.
A great choice of quality

car relays

for any car are available at Eurocarparts.com, should you need to replace any of the switches that control any of your car's electrically controlled systems.
 

Solenoid

Sometimes referred to as a starter relay, the starter solenoid is part of your vehicle's starting system. When you start your car the starter solenoid receives a large electric current from the car battery and a small one form the ignition switch. The starter solenoid then channels the appropriate current to the starter motor.
If you have a problem with the starting mechanism of your car that is diagnosed as the solenoid then

solenoids

for any car will be easy to find. Good quality

Solenoids

would be the best choice to ensure a reliable component for your vehicle.