Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology. A fuel pump relay can fail in several ways. Inner terminals may break, creating an electrical open condition; corrosion may build up around electrical contacts; contacts may burn, creating unwanted resistance; or the coil wire may brake, rendering the relay useless. Although a failed fuel pump relay — or any other automotive relay — will cause trouble occasionally, many car owners just go and replace a suspect relay and end up wasting money and time.
So, before you decide to replace it, test the relay to make sure it has actually failed. Let's go first over the basics of an electrical relay to help make sense of the following tests. NOTE: Here, we'll deal with electro-mechanical relays, not those that incorporate solid state or integrated circuits.
If you've worked with automotive relays before, you may want to skip to the tests sections. Here's the table of contents. What is an Automotive Relay? Physically, a common volt relay contains a series of electrical components set inside a small cube or cylinder box made up of hard plastic or aluminum. A common fuel pump relay has four electrical terminals or pins sticking out of its base. The terminals in an automotive relay hook up to an internal coil, possibly one or more resistors or diode, and one or more switches or contacts, depending on the particular configuration.
You'll see relays with 3 or 4 pins often, but others with 5 and 6 terminals are not unusual. These automotive relays come in different sizes and ratings.
And you'll find them under the hood inside the "block" or "power distribution center" box; inside the cabin, in fuse boxes under the dashboard; behind kick panels, and even mounted by themselves. They switch power on and off circuits around the transmission, engine and accessories like the fuel pump, the headlights, the brake lights, the wipers and horn. It helps to think of a relay as a regular switch, like the one you use at home to turn on and off the lights in a room.
A relay works in a similar way, but instead of you reaching into the relay to flip on the internal switch directly, you energize a control circuit that connects to a coil inside the relay — this happens to the fuel pump relay when you turn the ignition switch to fire up the engine, for instance. The coil creates an electromagnetic filed that closes a pair of metal contacts inside the relay that connect to a controlled circuit that activates a load — the electric fuel pump, for example.
Actually, this turned up to be a convenient set up in electrical circuits. You not only use a small, safer current circuit — the control circuit — to switch on and off a higher current circuit — the controlled circuit — but a relay can be placed in a strategic location to reduce the amount of — and expenses in — thicker gauge wire needed for high current circuits.
If you haven't located it yet, you'll need to find the fuel pump relay. Look inside the power center under the hood — a box with relays — or along the firewall or the fuse box es under the dashboard and side kick panels. On the back of the lid of these boxes you may find markings showing the relays they house and a short description of each.
On some vehicle models, you can find the fuel pump relay by itself somewhere underneath the dashboard or under the hood. Consult the vehicle repair manual for your particular car, if necessary.
Most auto parts stores carry aftermarket repair manuals for different vehicle makes and models, but you can buy it online too. Once you locate the relay, you have three methods to test it. Choose the most convenient. By far, the easiest way to test a suspect fuel pump relay — or some other automotive relay — is to swap the suspect relay with a good one.
You may find another relay in your car with the same configuration — arrangement and number of terminals — as your fuel pump relay. Or you can borrow a relay from a relative's or friend's car. Just make sure the other relay has the same configuration.
Remove the suspect relay and install the good relay and check if your engine fires up. If it does, install a new relay. Otherwise, the problem lies somewhere else.
Another way to test your fuel pump relay is with a relay tester. You can find testers to help you troubleshoot the most common vehicle relays and more sophisticated testers to troubleshoot relays with different configurations.The system took three years to build, and the first call was placed on August 17, Spencer Harding remembers climbing one of the towers in the Santa Monica Mountains as a high school student in the aughts.
He was intrigued by the hulking structure, especially its distinctive horn antennas, which transmitted microwaves to towers within line of sight. He did some research into the antiquated network, but didn't think to photograph it until years later when he regularly spotted the towers during highway drives.Micro bit 16: Using the Relay
I wanted to document as many as I could before they fade out. He found the towers, all of which are about 30 miles apart, through a Google Earth map created by a Long Lines aficionado. The skyway was the largest network of its kind when it opened, and it marked the first time telephone conversations and television broadcasts were made via microwaves, not transmission wires. Aftermore towers and repeaters were built across the country in an ever-expanding web.
Many towers—the tallest of which are hundreds of feet tall—were abandoned, vandalized, or scrapped. Some have been retrofitted for private communications networks, and a few people have had more enterprising ideas for the structures. One man on Mount Oso turned the small building at the base of his tower into a vacation cabin. Harding explored towers in the most remote areas, most memorably in Death Valley, where he wandered 40 miles down a dirt road along a bombing range to locate one tower.
But many of them were hiding in plain sight in urban areas, including downtown LA, Oakland, and Sacramento. As Harding plans the next installment of his project, he hopes the series will create a greater awareness of the network and a wider appreciation of its history. HectorMojave Desert, California. Mount Osonear Patterson, California. Privately owned. Lucerne Valleynear Victorville, California. Echo Summitnear Lake Tahoe, California.
Sugarloaf Mountainnear Redding, California. Salton Seanear Salton City, California. Santa Yneznear Santa Barbara, California. West SacramentoCalifornia. Gustinenear Gustine, California. Owlsheadnear Death Valley, California. Searchlightnear Searchlight, Nevada. View Comments. Sponsored Stories Powered By Outbrain.Whenever you operate a switch to an accessory in your car that carries a lot of current--such as the lights, wipers or horn--you run a small amount of current through a relay which, in turn, closes contacts to operate the accessory.
If one of your accessories doesn't come on and you suspect the relay is bad, you can perform a few simple tests. Look for the location of your relay in your owner's manual or in the fuse panel inside the car or under the hood. Turn the key to the "Accessories" position and instruct your friend to touch the relay while you operate the switch for the accessory that isn't working.
Your friend should feel a click in the relay when it operates. If not, you have a bad relay. Pull the relay out of its socket with the ignition off and insert a short piece of wire into the two connections of the relay that make contact when the electromagnetic coil pulls them together.
Look on the relay for a diagram of the pins. On a standard Bosch automotive relay, the pins are 30 and Operate the switch again to see if the accessory works. If it now works, the relay is bad. This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
To submit your questions or ideas, or to simply learn more about It Still Runs, contact us. Step 2 Turn the key to the "Accessories" position and instruct your friend to touch the relay while you operate the switch for the accessory that isn't working. Step 3 Pull the relay out of its socket with the ignition off and insert a short piece of wire into the two connections of the relay that make contact when the electromagnetic coil pulls them together.
Tips Most car relays pull out of a socket. Sometimes the relay vibrates out or works loose.
How to Test a Fuel Pump Relay and Other Automotive Relays
Try pulling it out and pushing it back in to fix the problem. On a standard Bosch relay there is also a pin labeled 87a. This is not the pin you want. Make sure it's labeled Warnings If you can't find a diagram for your relay, don't guess on the pins with your piece of wire.
You could short across the coil windings and blow a fuse when you operate the switch. Also, don't have your friend work under the hood with the engine running. Items you will need Short piece of to gauge wire, stripped at both ends. About the Author This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
Photo Credits 12 volt relais, relay image by Sascha Zlatkov from Fotolia.A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact formssuch as make contacts, break contacts, or combinations thereof.
Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays were first used in long-distance telegraph circuits as signal repeaters: they refresh the signal coming in from one circuit by transmitting it on another circuit.
Relays were used extensively in telephone exchanges and early computers to perform logical operations. The traditional form of a relay uses an electromagnet to close or open the contacts, but other operating principles have been invented, such as in solid-state relays which use semiconductor properties for control without relying on moving parts. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called protective relays.
Latching relays require only a single pulse of control power to operate the switch persistently. Another pulse applied to a second set of control terminals, or a pulse with opposite polarity, resets the switch, while repeated pulses of the same kind have no effects. Magnetic latching relays are useful in applications when interrupted power should not affect the circuits that the relay is controlling. American scientist Joseph Henry is often claimed to have invented a relay in in order to improve his version of the electrical telegraphdeveloped earlier in It is claimed that English inventor Edward Davy "certainly invented the electric relay"  in his electric telegraph c.
A simple device, which is now called a relay, was included in the original telegraph patent of Samuel Morse.
The word relay appears in the context of electromagnetic operations from A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core a solenoidan iron yoke which provides a low reluctance path for magnetic flux, a movable iron armatureand one or more sets of contacts there are two contacts in the relay pictured.
The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. The armature is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke.
This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board PCB via the yokewhich is soldered to the PCB. When an electric current is passed through the coil it generates a magnetic field that activates the armature, and the consequent movement of the movable contact s either makes or breaks depending upon construction a connection with a fixed contact.
Switch the right one
If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly.
In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing. When the coil is energized with direct currenta diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components.
Such diodes were not widely used before the application of transistors as relay drivers, but soon became ubiquitous as early germanium transistors were easily destroyed by this surge. Some automotive relays include a diode inside the relay case. If the relay is driving a large, or especially a reactive load, there may be a similar problem of surge currents around the relay output contacts. In this case a snubber circuit a capacitor and resistor in series across the contacts may absorb the surge.
Suitably rated capacitors and the associated resistor are sold as a single packaged component for this commonplace use. If the coil is designed to be energized with alternating current ACsome method is used to split the flux into two out-of-phase components which add together, increasing the minimum pull on the armature during the AC cycle. Typically this is done with a small copper "shading ring" crimped around a portion of the core that creates the delayed, out-of-phase component,  which holds the contacts during the zero crossings of the control voltage.
Contact materials for relays vary by application. Materials with low contact resistance may be oxidized by the air, or may tend to "stick" instead of cleanly parting when opening. Contact material may be optimized for low electrical resistance, high strength to withstand repeated operations, or high capacity to withstand the heat of an arc.The report on Micro Power Relay Market offers in-depth analysis of market trends, drivers, restraints, opportunities etc.
Along with qualitative information, this report includes the quantitative analysis of various segments in terms of market share, growth, opportunity analysis, market value, etc. The global micro power relay market is segmented on the type, application, and geography.
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For the Micro Power Relay Market research study, the following years have been considered to estimate the market size:. About Us Contact Us. By Name By Code. Request Covid - 19 Impact. Micro Power Relay Market Introduction 1. Definition 1. Taxonomy 1. Research Scope 2. Executive Summary 2. Key Findings by Major Segments 2. Top strategies by Major Players 3. Micro Power Relay Market Dynamics 3.
These cookies are set when you submit a form, login or interact with the site by doing something that goes beyond clicking on simple links. We also use some non-essential cookies to anonymously track visitors or enhance your experience of the site. If you're not happy with this, we won't set these cookies but some nice features of the site may be unavailable. If you would like to know more about TE - te. KISSLING is a trusted partner for OEMs and fleet operators alike — we cover a large range of high power, high voltage and control switching applications on all types of commercial vehicles.
Dust, moisture, extreme temperatures… Construction equipment needs to perform reliably in a variety of extreme environmental conditions — and the sealing technology in KISSLING relays and switches is optimized specifically for these application areas. At KISSLING, we understand the importance of reliability in a mil-spec part and we have been supporting manufacturers of ground support and tactical vehicles for decades with unparalleled products and know-how.
E-Vehicles, Hybrids, Charging stations and Power management systems — all part of a fast growing industry that bring new and challenging application requirements to light. Travel coaches City buses Shuttle buses Hybrid buses School buses. E-Vehicles Hybrid vehicles Charging stations Power management systems. The KISSLING brand is synonymous with ruggedized and sealed switching solutions of uncompromisingly high quality, designed for extreme operating environments including shock, vibration, temperature and humidity.
Whether you are planning a new production vehicle, having trouble with your current components, or you simply want to get the best for your money — come talk to us and we will be glad to help you find the right solution for your needs.
With our reputation for uncompromising quality and extreme reliability, KISSLING has established itself as a best-in-class supplier in our industry segment. Even as we continue to grow and expand, we pride ourselves on the ability to develop and maintain close working relationships with our customers in all the markets we serve, understand their requirements and provide both standardized and custom switching solutions.
For more than 70 years, KISSLING has proven its ability to address military and industry requirements for robust switching solutions for mission critical applications and demanding environmental operating conditions.
Our innovative designs and uncompromising attention to production quality and product reliability result in a product line of relays and switches for both power distribution and control applications. We are proud of our certifications, but it is really the attention to detail and the people behind the scenes that guarantee the high quality levels of our products.
KlSSLING products perform exceptionally well wherever switches and relays need to operate reliably under extreme conditions for demanding applications. KISSLING has built its outstanding reputation on solving customer requirements for switching applications with very high contact ratings, critical environmental conditions such as humidity, pressure, dirt, aggressive fluids or increased shock and vibration stability.
Our broad spectrum of quality relays and switches combined with the wealth of experience resulting from years of practical application work, makes KISSLlNG your essential solution partner for applications with exclusive switching requirements. If you have an application that cannot be solved with a mass produced, industry-standard part, then talk to us!A relay is essentially a switch that is operated electrically rather than mechanically.
Although there are various relay designs, the ones most commonly found in low voltage auto and marine applications are electro-mechanical relays that work by activating an electromagnet to pull a set of contacts to make or break a circuit. These are used extensively throughout vehicle electrical systems.
This is the most common reason and useful where an in-line switch or the existing circuit does not have the capacity to handle the current required. For example, if you wanted to fit some high power work lights that come on with the headlights but there is a risk that they would exceed the capacity of the existing loom. High current capacity wiring and switches cost more than lower current capacity versions, so by using relays the requirement for the more expensive components is minimised.
You can use a single input from one part of an electrical system e. Although these logical functions have now been superseded by electronic modules for OEM designs, it can still be useful, fun and often more cost effective to use relays to perform them for some after-market projects particularly where you have a bespoke application.
Note: In this article we are going to focus on ISO mini or 'standard' relays which have a 1" cube body and are the most commonly used in vehicle electrical systems. A copper coil around an iron core the electromagnet is held in a frame or 'yoke' from which an armature is hinged. One end of the armature is connected to a tension spring which pulls the other end of the armature up.
This is the relay in its de-energised state or 'at rest' with no voltage applied. The braided bonding strap provides a good electrical connection between the armature and yolk, rather than relying on contact between the armature pivot point alone. The coil and contact or contacts are then connected to various terminals on the outside of the relay body.
When the coil is supplied with voltage a magnetic field is generated around it which pulls the hinged armature down onto the contact. This completes the 'high' current circuit between the terminals and the relay is said to be energised. When voltage is removed from the coil terminal the spring pulls the armature back into it's 'at rest' position and breaks the circuit between the terminals.
So by applying or removing power to the coil the low current circuit we switch the high current circuit on or off. The coil circuit simply switches the high current circuit on. The following simplified circuit diagram is often used to easily understand how a relay operates:.
Normally Open relays are the more common type. These have two contacts connected to a common terminal. This is based on standard switch terminology. The terminals on the outside of a 4 or 5 pin mini relay are marked with numbers as shown below:.
The automotive ISO mini relays we have been looking at above are typically available in two types of pin layout designated Type A and Type B layouts. These layouts are shown on the two 5-pin relays below pin 87a not present on 4 pin relays :.