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Old 08-10-2022, 11:36 AM   #7
fdryer
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Join Date: Jan 2006
Location: NYC
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2003 L-Series 3.0L Sedan
Default Re: 4-Pin Relay Orientation?

Quote:
Originally Posted by N147JK View Post
So, pin 30 always goes on the battery power socket. I checked the sockets with the power off. Interestingly, in 2 cases (the 2 smaller relays) there are 2 pins that both have 12 volts on them. One is the horn relay. I found that the horn works exactly the same regardless of which way the relay is inserted. I guess there are normally open and normally closed type relay circuitry.
All 87a relays are configured (no power to the relay coil) with normally open contacts (30 and 87). A command to send power to the coil closes contacts 30 and 87. Some circuits like the horn need 12v on either 85 or 86 since the horn works without turning on ignition.

If I'm not mistaken, you're examining the relay wiring for the ac clutch. I mentioned leaving the ignition switch OFF when probing for 12v on the four relay socket terminals of the ac relay. If you turn ignition ON, the ignition switch distributes 12v to various circuits, one of them is the ac relay on either 85 or 86. If you have ignition ON, there will be two relay socket terminals with 12v on them. This can confuse anyone unfamiliar with relay circuits. In this case, leave ignition OFF so you won't be misled by a second 12v source on the four relay socket terminals.
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