Think of relays as remote control switches. When you turn a device on or off, the button you press sends a current to one side of the relay. The other side actually switches the device on or off. This is a bit simplistic, but relays provide a safe way of powering devices that take more current than would be safe with a small switch. You can hear the relays activating as you activate switches in the car. The loudest one is probably for the A/C. While you're driving with the A/C on you will hear the click of the relay as the compressor turns on and off. Some of these are the same rating, but they are not all interchangeable so don't ever try to switch them back and forth or anything. KermitP -------------- Original message from "daviddelorean" <daviddelorean@xxxxxxxxx>: -------------- I replaced all my fuses and those square electric relays when I bought my car. Exactly what do those square relays do? There are a bunch in the electric box behind the passenger seat and one in the engine compartment. The new ones are plastic, not metal. When you put accessories 'on' the relays make a CLICK sound. I don't know if US made cars have them. [Non-text portions of this message have been removed] To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/dmcnews/join (Yahoo! ID required) <*> To change settings via email: mailto:dmcnews-digest@xxxxxxxxxxxxxxx mailto:dmcnews-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/