AC relay always has power on 85 and 86. This is with key on. Compressor runs constantly. I’ve removed relay so my son can drive(his truck). I’ve pinned out to ecm with good continuity, both low and high plugs. Also pinned clutch control. Chased back to relay center under hood. Pin 85 and 86 both have 12v. Help please

 

If 85 and 86 both have power, the relay shouldn't be energized. One of those (85?) needs to be grounded. Is it possible that 30 and 87 are shorted internally in the relay?

 

swapped multiple relays. No change. Probed the relay block under hood with relay out and verified 12v on both with key on. Separated wires from ECM all way across to relay block. No shorts, burns, anything. Does BCM control ac clutch?

 

Give me the vitals on your Blazer and I'll find a wiring diagram.

 

1999 4dr 4x4, LS. Standard options nothing fancy.

 

Here you go.

 

thank you. This shows what I’ve seen one leg hot all time, second leg hot on key. Guess I’ll keep chasing it. Something isn’t commanding clutch to unlock.

 

The PCM should ground one side to engage the clutch.

 

That points to an internal PCM failure. I’ve already verified continuity from pins to ground at PCM plug on all blk/wht. Oh well thanks for the help

 

Sorry I don't have a better answer for you. Good luck.