All relays on the engine fuse & relay box diagram have the pin numbers reversed on my '03 Tahoe...

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Rocket Man

Mark
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You can turn those around and they'll still work. The pinout diagram is correct; it just doesn't matter which way those particular 4-pin SPST relays are installed. Otherwise the pins would be offset so they can't be installed backwards which would most likely start a fire or at least immediately blow fuses. If you look at that diagram on the side of that relay, 85/86 is the side that gets energized and 30/87 is the side that is the switch that closes when 85/86 gets energized. If you turn the relay around, 85/86 still go to the same 2 locations but 85 goes to where 86 was and 86 goes to where 85 was, and it's the same for 30/87. It doesn't matter in this instance when these relays are used this way. The only way that would matter is if 87a is used; that's where the other side of that switch contact rests when the relay isn't energized. The flyback diode is only used on the 5-pin relays even if pin 87a isn't used, for the same reasons stated above. It's used in instances where the circuit needs to be protected from voltage spikes and obviously these instances don't need that protection.
 
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xDan

xDan

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Yea that's pretty much what I figured out. You are right @Rocket Man with those circuits not needing the freewheeling functionality except for the A/C comp and fuel pump relays... The freewheeling functionality is on the control sides and those might be switched by the bcm or ecm. I put them all back the correct orientation. I checked the fog relay, there is no slot on the opposite side of 87a so you can't put that one in backwards.
Anyways, the reason I was looking at them in the first place was to do the 6-hi mod. So here is my rendition: It cost me nothing as I had all components on hand. Instead of a 1N4004 I used a 1N4007, heatshrink, about 3" of M22759/20 which is a 20 gauge PTFE coated wire and 2" of solder.

IMG_20171117_205322.jpg
 

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