|
|
|
|
|
#31
10-04-2007, 10:10 AM
|
|||
|
|||
|
Once you let go of the starter switch, relay goes from 87 to 87a and the clutch kicks on again. > Very Good.. It just interupts the a/c when trying to start, reasons being they want as much starting capacity as possible and they also do not want the car trying to start with head pressure on the compresor ..this would happen if one did a quick stop , like at a gas station or quick run-in at a store without turning off the a/c before stopping the engine. When you came back to start the car , the high side pressure of the a/c system could still have high head presure and the starter would have to fight that extra drag. Starter Activated A/C Interupt Relay For any readers..a good piece of relay info to remember: A 5 pin automotive relay has the #87a terminal, where a 4 pin does not have this extra contact set. This is always an "a" terminal, and any time you see this 'a' after a terminal #, it means this terminal is connected to terminal 30 inside the relay when there is no activation feed to the relay coil. In other words ,this circuit is CLOSED when the relay is at REST. It only OPENS that circuit when the relay is energized [ just the OPPOSITE of a standard 4 pin relay] If you took this type relay and unplugged it, it would show continuity between 30 and 87a w/o even being hooked up. If it did not pass that continuity test, it's interior contacts are bad. These 5 pin types relays are used on many car applications/circuits, so this is a good rule to have in mind. That extra contact set [ 87a] is the only difference between a 4 pin and a 5 pin. You have all seen switches that have a Nornal Open and Normal Closed connections marked on them [ NO/NC ]..well, the 5 pin relay has both ..with this extra contact set, the relay can be used for either Norm Open circuits and Norm Closed circuits, depending on which terminal you use. It is just a SPDT relay, whereas the 4 pin is just a SPST relay..............one can see where the 5 pin has way more circuit application flexability than the 4 pin. http://members.aol.com/ajdalton7/relay.jpg In the above a/c post , you can see that they are actually only using 1/2 of the 5 pin relay. The other normal open contact set is not needed for that application, but they needed a normal closed set-up, so they still had to go with the 5 pin relay, even though they are only using 4 of the pins. [ the standard 4 pin relay does not have a normally closed contact set, so it is therefore not applicable for this type a/c circuit] Last edited by Arthur Dalton; 10-04-2007 at 05:57 PM. 
|
 |
| Bookmarks |
|
|
Linear Mode
