• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Relays

Share this page

TR674

TR674

Jedi Warrior
Offline
For those of us who know nothing about auto electrics, what is the purpose of a relay and why are they fitted to the overdrive, horn, etc circuits?
I noticed that the original relays on my car have been replaced with non genuine ones. Do they wear out and need replacing? I don't have any probs with my relays, just curious.

Regards
Craig
 
Hi Craig,

These relays are switches capable of handling a heaver load. They are activated when you push your horn button, headlights, starter switch, or other remote switch that is not designed for a high current load. In other words they make it possible for you to not have several large bulky switches mounted on your steering wheel or dash. In other words these relay(switches) relay the low amperage circuit into a higher amperage circuit.
 
Aloha Craig,

I think of a relay as a remote electrically actuated switch. The relay allows you to use smaller wire from the dashboard to operate electric devices with a high amp draw. A starter solenoid is basically a relay, that small wires from the ignition switch electrically activating the solenoid connecting the heavy battery cable to the starter. The alternative would be a thick battery cable to the ignition switch itself and another cable to the starter motor.

A relay generally uses an electro magnet to close the relay (switch) which is energized when you close the dash switch. The probable cause of failure are the magnetic coil circuit opens, perhaps the soft iron core corrodes in place or the contacts in the relay become pitted because of the heavy load they carry.
 
TR674 said:
For those of us who know nothing about auto electrics, what is the purpose of a relay and why are they fitted to the overdrive, horn, etc circuits?
I noticed that the original relays on my car have been replaced with non genuine ones. Do they wear out and need replacing? I don't have any probs with my relays, just curious.

Regards
Craig
Click to expand...

Craig, again I will refer to Dan Masters' book on TR250-6 Electricals. A virtual bible on everything from relays to light bulbs. Makes a novice into an expert. Moss Motors has them.
 
Back
Top