If anyone is around that knows wiring well, sure could use some help understanding what is going on with my 68 with factory AC. I've seen a lot of old posts on wiring that have been helpful.
The relay on top of my AC box under the hood has a 3-wire connector. The black with orange strips comes from the alternator with a newer in-line blade type 30 amp fuse. The purple goes to the blower motor. The dark blue goes to the resistor. Then there is a separate brown wire that comes from the firewall connectors on the drivers side with what I think is an original "blower motor" label and original style plug that is not connected to anything.
I know that the black with orange stripe has been modified since it has the newer blade-type inline fuse, but I believe it still would have connected to the alternator. I can't tell if the purple one going to the blower motor is a modification from original or something OE that I can't find in the manual. The blower seems to work fine.
The car has a POA eliminator and Sanden compressor, but the wiring for these seems separate from what I have going on at the relay.
Other side questions - the plug with the dark blue, light blue and yellow going into the resistor is badly melted. Are the plugs available anywhere, and I assume this is a sign that the resistor has or had a problem?
And with the black with orange stripe wire coming from the alternator, is there a reason I can't have that come from a 12V buss rather than straight off the alternator, in an effort to clean up the wiring?
Thanks for any help, and definitely ask for clarification if you need more info.
First, I can't claim to be someone who "knows wiring well" but here's my comments anyway.
When I was going through my known original AC wiring many years ago I got all confused looking at the one in the 1968 Firebird Wiring Diagram. I too have a purple wire to the blower motor like yours and that manual shows a "spliced" orange black. Not only did my car not match the diagram, the diagram didn't make electrical sense. Then, I found another diagram in the 1968 Pontiac Diagnosis Manual that appears to be accurate. (Attached)
I personally would not change the routing of the orange/black from the fused alternator connection. I don't know the actual current draw but a 30A fuse implies a hefty one. Adding that draw to some other 12V source would add a significant additional current to the wires feeding it. My 30A fuse holder saw better days so I found an original type holder to duplicate the original appearance. I would assume the blade one you have would be fine.
Finding connectors can be challenging. Somehow harness repro manufacturers find sources. Maybe someone else here will know a source.
That was the missing link! Matches exactly what I have. So I guess the brown lead labeled with "blower" or "blower motor" that comes from the firewall bulkhead connector must be for cars without AC and they just left it in the harness. I'll have to see about tucking it away or maybe removing it and documenting it if possible just to clean things up since this is not a full return-to-original car.
That is a good point about the alternator source for the 12V supply wire. It's already a good size, probably 12 gauge. I was thinking about adding a buss bar near the battery but getting power from the alternator wiring and would have to upsize some wiring to achieve that, but I don't know if I want to go to all that work.
But that diagram answers all my questions, so relieved. Thanks again!
Wow, that one is great, lots of detail. I like that it shows the wire size. I may have to look into getting that diagnosis manual, seems really handy. Thanks again!
