Engine bay AC wiring diagram??

[BigPoser]

I'm in the process of re-wiring my entire 73 front to back. One part that didn't come with the kit (American Autowire), because it isn't available, is the wiring for the AC system within the engine compartment and I can't find one to save my life.

My AC didn't work prior to the re-wire, but I think it's because of the many wires that didn't go to anything, but started at either the compressor, or HVAC.

Anyone here have any wiring diagrams that might help me out?

Thanks in advance.

Brandon

 

[chengny]

Wiring diagram for a 1973 with the 4 Seasons AC system:

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[BigPoser]

Wiring diagram for a 1973 with the 4 Seasons AC system:

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I knew if anyone would have it, it was you. Thank you sir!!

 

[BigPoser]

Wiring diagram for a 1973 with the 4 Seasons AC system:

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Thanks for this again. After looking at this wiring, it seems that it's missing a portion of wiring that I have for a blower relay.

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Any thoughts as to what goes to this relay? Also, where would I get the female connections for said relay? I can't find them anywhere.

P.S.- All my AC wiring is good on the passenger side of my truck until it runs to the driver side of the truck where the blower relay mounts on the firewall.

 

[chengny]

Any thoughts as to what goes to this relay? Also, where would I get the female connections for said relay? I can't find them anywhere.

That is the blower relay. It is shown in the yellow box in the dwg below. It mounts on the outboard side of the evaporator housing and has 5 leads connected to it. Black and little orange go to the double tab connector. Dark blue, purple and big orange to the triple tab connector. When the time comes to wire it up, we can figure out which leads go where by looking at the diagram on the relay shell.

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What you describe below is not the blower relay. I can't imagine what it is - there are no electrical components associated with the HVAC system on that side of the engine. You aren't talking about the firewall junction block, are you?

P.S.- All my AC wiring is good on the passenger side of my truck until it runs to the driver side of the truck where the blower relay mounts on the firewall.



Here are some dwg's - and pages from the 1973 Service Manual. They have lots of good info in them:

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Look through them and I'll be back to help you tomorrow. I've been on this for a while and need to crash.


On this:

Also, where would I get the female connections for said relay? I can't find them anywhere.

If you can't source the OEM harness connectors, it's no big deal. Just go to an electrical supply house and get a box of the correct size solderless/crimp-on connectors. They will be fine.

 

[chengny]

Saw this on ebay while looking for a part for my truck this AM:

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It looked familiar to your missing part and has the correct number of tabs in the correct locations. Only $25 - buy it now - and $3 S&H:

http://www.ebay.com/itm/70-71-72-ch...163220?hash=item2ca4021e14:g:li4AAOSwk5FUsxsP




A little research revealed that it does cross-reference to your AC blower relay (part 1115858). See the images below as explanation. Apparently it was a very common relay used for many different applications across all the GM divisions/model lines:

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https://www.thepartsplaceinc.com/classiccarpartsdetail.aspx?partNumber=AC12600Z


If I were you, I would snatch that up - like now. Great price . I only saw two relays with the 1115858 part number. One was $100 and the other was $185.

 

[BigPoser]

Chengny,

You are the man. Thank you so much for this. From what I can see, everything regarding on the passenger side engine compartment is golden. From the diagram it looks like there should only be a dark green wire that goes directly to the compressor, then to ground.

As you have pointed out it is not the part that I'm thinking of. I'll grab a pic of the specific piece that I'm trying to figure out. It is mounted on the fire wall just above where the column comes through. I'll also take a pic of another mysterious part of the wiring that tied into a small block that was on the driver inner fender. Some strange stuff going on. Thanks again for the help on this.

Also where did you get that service manual? I'd like to grab one if possible.

Brandon

 

[chengny]

Here, I just uploaded the 73 service manual and the 73-78 parts list and parts illustration manuals. Files are zipped - no PW required.

1973 Light Truck Service Manual:

http://depositfiles.com/files/i8f1ijt7y

1973 -1978 Parts List and Illustrations :

http://depositfiles.com/files/t2bvvkrh1

http://depositfiles.com/files/sl7slquc5

I use Deposit Files for file sharing. It is free and safe - you just have to x-out a couple of pop-ups sometimes while waiting to download.

 

[BigPoser]

So here is the part that I'm referring to. Not sure what it is and I can't tell from the old wiring that I removed from the truck what it goes to because it didn't go anywhere.

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This is a portion of the AC wiring that I mentioned above that is on the driver side of the truck. This is how it was when I got the truck. As you can see, it also goes nowhere and it's pretty hard to decipher where it goes.

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I was able to find a manual on amazon too. Thanks for the help on this man I appreciate it greatly.

Brandon

 

[chengny]

So here is the part that I'm referring to. Not sure what it is and I can't tell from the old wiring that I removed from the truck what it goes to because it didn't go anywhere.

I have no idea what that box is either - but I can assure you, it's not part of the A/C system.


This is a portion of the AC wiring that I mentioned above that is on the driver side of the truck. This is how it was when I got the truck. As you can see, it also goes nowhere and it's pretty hard to decipher where it goes.

Don't even try to figure it out. It is not original and (other than the lead that goes from the compressor to the connector - which you should try to keep for the compressor plug) none of it is needed or helpful. Just from what I can see in the images, it appears that someone replaced the original compressor - with one from a later model year - at some point. Most likely they used that end section of the harness as well - probably because the original harness plug configuration didn't match up with the donor compressor.

**** the compressor power lead off where indicated by the arrow, save the outlined section of wire - then throw everything else away. It will just confuse the issue (and make your engine compartment look like crap) :

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That remaining pigtail of wire needs to be extended. Splice a 10 foot or so length of 12/14 gauge wire on to it and run it back to the firewall, then it goes across the engine compartment and terminates at the evaporator temperature control switch. I have to assume that you have no high pressure cut out switch so that isn't an issue. If you do have that component and it still works, run the lead from the compressor through that first - rather than directly to the ETC switch.

All you are doing is replicating the original wiring harness from the ETC to the compressor (and skipping the high side safety switch). The new wire is schematically the same as the lead traced in blue below:

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Over on the RH side connect the homemade lead to one of the terminal tabs on the ETC (doesn't matter which one). The ETC switch is - or should be - mounted on the outer side of the evap housing as shown below:

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After you have made up the load side of the ETC switch the only thing left to do is locate the DK GRN/WHT power feed that comes from the mode select switch and run it to the other tab on the ETC switch. That lead will penetrate the firewall at the common rubber grommet (along with the fan control wiring and the vacuum supply tube). It is represented by the red ( I think it's red anyway - little colorblind problem) tracer in the wiring diagram above. At that point you will have completely wired the control circuit for the compressor clutch.

All that will remain will be to wire up the blower control relay and blower resistor stack.

 

[BigPoser]

Chengny,

Thanks once again. As stated it just looks weird that nothing goes anywhere. I do have a portion of the dark green wire that comes from the tempurature control switch but doesn't quite make it to the compressor.

On the compressor itself that green wire goes into a two wire plug (nothing is on the other side, but assume it's for a ground).

I'll be working on this again after vacation later this week and hope it all goes well. The good thing is that summer won't be back for a while and don't need the AC not anyway. Thanks again for your help.

Brandon

 

[chengny]

I do have a portion of the dark green wire that comes from the tempurature control switch but doesn't quite make it to the compressor.

As above:

That remaining pigtail of wire needs to be extended. Splice a 10 foot or so length of 12/14 gauge wire on to it and run it back to the firewall, then it goes across the engine compartment and terminates at the evaporator temperature control switch.

On the compressor itself that green wire goes into a two wire plug (nothing is on the other side, but assume it's for a ground).

Yeah, you got it. Just make up a jumper with the proper sized female spade connector on one end (to mate with the the unused tab on the clutch ) and an appropriately sized ring terminal on the other end.

Push the end of the wire with the female spade onto the open tab and find a convenient nearby bolt/stud to ground the ring terminal.