Homepage

1. Engine Basics

2. Advanced Engine Tuning + Forced Induction

3. EFI Tuning

4. Chassis Tuning

5. Misc. Information

6. WHAT'S HOT in Auto

7. New Products + Tools

8. All Wheel Drive Civic Type RL

Contact Us

 

DOT Help

Department of Transpertation

Understanding Automotive Relays

Article By: enginebasics.com

First you should know that a relay is just a device that when given a certain voltage will apply that voltage to other parts. Think of it like a train yard….a single train will come into the yard, and then be broken up and send the cars many different directions. A relay does the same. It takes the incoming voltage and once grounded will send that voltage to other places. So lets just focus on what an automotive relays is. You will usually see 3, 4, and 5 prong relays.

An automotive relay will be working with either a 12v or 5v signal. 12v, the standard of all automotives batteries, and 5v the standard for automotive sensors. For this article, lets just assume we are talking about standard 12v relays. Every relay should have a diagram showing what the relay does. Here are some examples: The squiggly line represents what we call: the coil. This is the part of the relay that switches or moves when it receives its desired voltage…..12v. Once it receives its 12v, it will then throw the “switch” to make continuity (attach) the other inputs and outputs. So lets use the diagram below( click for larger image):

Pin 85 and 86 are the coil. So we will hook one up to 12v, and one to ground. This way when the relay receives either voltage or is grounded the relay will jump into action. So when it does “jump into action” what will it do? Well in this case it will take whatever voltage is on input 30 and switch it from outputting on pin 87A to pin 87.

Some of our favorite relays that we use:

So how could we use this?

Well maybe the above relay is for your headlights. When you turn your headlights on you send voltage to pin 30 which when the relay is not active sends it right out to pin 87a, which happens to be your low-beams. Also lets set up the scenario by telling you that Pin 85 and 86, which are the coil, pin 86 is grounded but pin 85 currently has no voltage. Now you go to turn on your High-beam headlights. Once you do this, pin 85 receives 12volts and the coil energizes, flipping the relay from outputting pin 30 from 87A over to 87. Well it turns out 87 is hooked to your High-Beam lights. So what happens….your low beams turn off on pin 87A and your high beams turn on because of pin 87. While this is just an intro to looking at automotive relays, I hope this give you enough understanding to test them and read more about not just automotive relays, but relays in general.

***Remember*** to check for other relevant information in the columns and article tables.

ATTENTION READER:

If you enjoyed the information and article you just read be sure to check out our newly released book with even more exciting photo's and information:
How to Turbocharge and Tune your Engine

Follow Enginebasics on...

Want to know more about your particular Make and Model vehicle? All of these vehicles are covered in the tech, maintenance and repair articles found above. Enginebasics is the wiki or wikipedia of car part, repair, how to and tuning information. Let us be the class 101 for your automotive learning.

Individual Models

Below are just a few of the articles found here on enginebasics.com

Reading Spark Plugs	Camshaft Understanding	Engine Timing	Intake Runner Length	Exhaust Flow Tuning	Camshaft Timing	Engine Cooling Basics	Compression Testing	Forced Induction
Tuning A/F Ratio Basics	Intake Manifold Basics	A look at cooling mods	Camber Caster Basics	Sequential Vs Batch Injection	Fuel Pressure Regulator	EGT Vs A/F EFI Tuning	Engine Start Programming	What is a fuel Injector?
Brush vs Brushless Motors	4-stroke motor diagram	Crankshafts Basics	Automotive Relays	EFI Tuning Basic Thoery Guide	Understanding Electric Motors	Water Meth Injection	Intercooler Basics	e85 Basics
Water to Air Intercooling	Turbo Surge	EFI Air Intake Temp Tuning	Map vs. MAF Sensor EFI Tuning	Engine Start up tuning for EFI Cars	Building an EFI Surge Tank	Intercooler Efficency	Boost Controllers	Engine Oil Weights
Exhaust Cutout Basics	Cold Air Intake vs Short Ram	Engine HP and Torque Basics	Intercooler Sprayer Basics	Turbo Manifold Design Basics	Cryo Liquid Co2 Cooling	Oil Cooler Basics and Installation	Boost by Gear Tuning	Closed Loop vs Open Loop O2 tuning
Changing your own oil	Static Vs. Dynamic Compression	Air to Air Vs. Water to Air Intercoolers	Vented vs Recirculating Blow Off Valves	Engine Intake Exhaust Valves	Wiring a fuel pump relay	Synthetic vs Regular Oil	O2 Sensor Repair Fix	Embrace the TURBO LAG

**TO SUBMIT AN ARTICLE TO ENGINE BASICS PLEASE CLICK: CONTACT US!

Testimonials Page

“Thank you, for the info, on your site, on how to remove valve springs, and install stem seals, using normal shop tools. Info from every other site I looked at, only said how to do it using costly special tools. Thank you for showing the REAL easy way, and saving me some money.”   Joe S

“Hello there,
            Don’t have any questions, just wanted to say thanks for putting this info out there.  So much mis-information on forums, good to read some solid info. Peace” Jay R.

Privacy policy and terms of service

Advertise

Copyright 2010 EngineBasics.com: Engine Basics. All Rights Reserved

Enginebasics Google+ Page