I may be buying a mass air conversion for my 87 mustang, and I heard that only the 89 harness is a direct swap. so, how can I tell if the harness I'm getting is from an 89?
I'll assume your talking about the computer harness itself. If that's the case 89-93 are all the same. You could always just get a MAF conversion for $40 and just wire it into your existing harness........ a lot of people do it that way too.
89-93 engine harness's are definately not all the same. I put a 93 harness into a 90 body and none of the guages worked,fuel pump didn't work. Had to move a couple wires around in the connector at the drivers side firewall/inner fender area. Not to mention 89 is a non air bag mass air harness. Your best bet is to use the same year harness as your car... or 89 mass air harness into 87-89, 90-92 harness into those corresponding years and 93 harness into 93 cars. The 93 harness has a brown plug on it.
Or like ram360 stated, there is a cheaper way of converting to mass air. I think its like a 5 or 6 wire deal and not much more, if any, money than he said.
Iv your going to use a OEM harness the 89 is the one to get, otherwise just get the cheaper conversion harness. I have a 89 harness and computer but haven't converted yet, it's been sitting for over a year now. I'm just seeing how far I can push the SD before I need to switch over.