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        General >> Give/Need advice to/from others >> Testing a relay
        
(Message started by: tonyboy on Dec 17^th, 2009, 11:01pm)

Title: Testing a relay
Post by tonyboy on Dec 17^th, 2009, 11:01pm

Hello. How do you test a relay to see if it's working or not. I want to check to see if my front windscreen heater relay is working...... Cheers

Title: Re: Testing a relay
Post by gozz on Dec 17^th, 2009, 11:40pm

Most relays are merely an electromagnetic switch whereby the side operated by the switch for the equipment to which it is connected, closes a pair of contacts which pass the heavier load to that equipment,thus preventing switch overload.There are various types but most carry this general priciple,therefore if your relay has four pins,two will operate the electromagnet via the switch,the other two passing the current to the windscreen.Many have the schematic diagram on them making testing easier.Find out which pair closes the contacts by listening for the click,if it doesn't click it isn't working,then connect another live to one of the other pins,and a grounded lamp or meter to the fourth,when the relay clicks the current should flow through to you lamp or meter.
GOZZ.

Title: Re: Testing a relay
Post by tlundkvi on Dec 18^th, 2009, 10:19am

A question related: are the relay markings like 78, 85a, 86 etc. standadised wrt. their meaning in circuits?