How long can a relay be "on?"
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=11989
Printed Date: May 23, 2024 at 1:50 AM
Topic: How long can a relay be "on?"
Posted By: stanward
Subject: How long can a relay be "on?"
Date Posted: April 09, 2003 at 4:55 AM
Hello all, How long can the coil of a standard automotive relay be energized? I understand that the relay coil will produce heat that determines the lifetime of the relay. Anyone have an insight to my question? Thanks, Stan
Replies:
Posted By: greenbroncoguy
Date Posted: April 09, 2003 at 5:54 AM
i wouldn't tink that a relay would "go bad" just from being left on. the running lights on your automoblie are turned on using a relay when your head lights are on, and some lights are left on a long time wich means that relays are left on a long time also.
Posted By: sufferrar
Date Posted: April 09, 2003 at 9:11 AM
This has my interest too.
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"I'm So Loud It Hertz"
Posted By: ggrizzle
Date Posted: April 09, 2003 at 12:56 PM
I have done a lacthing relay on some neons and i leave them on alot while my car is parked. I have had it installed for about two years now and i have never had no problems. i would think a relay that is on for long periods of time will burn out quicker than one the is just pulsed momentary from time to time. Just my thoughts on the subject. I know that the headlights and parking on vehicles have relays that control them and they last for years and yearsWhat is it exactly you are trying to do, if we know maybe I or someone can better assist you? ------------- G.G.
Posted By: stanward
Date Posted: April 09, 2003 at 1:49 PM
I'm using a DEI relay, with a 90ohm coil resistance. I plan to use it to control my aftermarket power windows. The ignition power will switch the relay "on" and I will fuse the supply of the relay before it goes to the window motors. Thanks for the replies, keep them coming! Stan
Posted By: the12volt
Date Posted: April 09, 2003 at 2:18 PM
I've had Bosch and Potter & Brumfield relays connected behind displays that have literally stayed on for years with the exception of a few power outages, but if you want a more accurate figure, check the manufacturer's specifications on the relays you are using. They will provide you with expected mechanical and electrical life ratings (usually at minimum) and typically will be far beyond what you will require. I've yet to have one go bad simply because it was left on too long. -------------  the12volt • Support the12volt.com
Posted By: Haku
Date Posted: April 09, 2003 at 10:06 PM
Think of it this way.... most electic fuel pumps run off a relay.. a standard 30A relay, so whenever the car is running, the relays is "on". Of course, amp draw on the output of the relay, if excessively high, can shorten the life of the relay. These fuel pumps usually draw 8-15A max. So, for most aftermarket applications, a relay will last a very long time. ------------- Hak
Siemens Autostart
Posted By: ViperATC5
Date Posted: April 09, 2003 at 10:16 PM
when a relay is "on" - that only refers to the relative position of two contacts. When the relay is energized, it "clicks" and the contacts move - technically the relay is at rest untill that energy is gone, then the relay will click again and be back in the rest position. The only time the relay is actually doing anything, is while it is actually switching
Posted By: cpgoose
Date Posted: April 10, 2003 at 8:29 AM
This is interesting....
This is why I'm a little reluctant to implement one of the fuel cutoff methods I saw, which would switch a relay on while the car was running, and stay on while the car was running. I'm a little afraid the relay will die while I'm driving, and the car would shut off.
Posted By: chuckles
Date Posted: April 10, 2003 at 5:34 PM
A relay will last for almost ever, as long as the voltage to the coil, electromagnet, is not exceeded. I've put automatic transfer switches in hospitals and gone back 25 years later and they still have the same relays. The relays control the emergency generator and are latched constantly by the power company so when they loose power the relays drop out and start the generators.
Posted By: 88RX7T2
Date Posted: April 11, 2003 at 11:59 AM
When you use a relay for a starter kill or Fuel cutoff the relay will be close( not energize) providing current to the fuel pump until the alarm goes of,then it will move to the open position and wont let current pass trough it. So, basicly relay just makes the starter or the fuel pump stop working while the alarm is on if you wire it correctly. You dont have to worry while you driving because it will be at rest.
Posted By: cpgoose
Date Posted: April 11, 2003 at 2:30 PM
Well, I was referring to this page. I thought it would stay on while the car was running, letting the fuel pump supply fuel. Do I have this backwards? That would be cool, because I think this is one of the best setups I've seen.
Posted By: stanward
Date Posted: April 11, 2003 at 2:43 PM
I believe for an OEM fuel pump relay, the relay is energized when the ignition is turned on. The car will be driven a lot less than when it sits around, etc. I think that is correct. Stan
Posted By: TBmojorisin
Date Posted: April 11, 2003 at 9:39 PM
chuckles wrote:
A relay will last for almost ever, as long as the voltage to the coil, electromagnet, is not exceeded. I've put automatic transfer switches in hospitals and gone back 25 years later and they still have the same relays. The relays control the emergency generator and are latched constantly by the power company so when they loose power the relays drop out and start the generators.
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