May be why the air doesn’t work...

[chengny]

These wiring diagrams for the 1984 models are real nice:

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[chengny]

Could use some help getting my AC and heat working. Poor bastard I bought the truck from must have been color blind. Has all kinds of different wires tied together. This looks like the blower motor switch but I can’t get power going to it. Anyone have a diagram or could walk me through? I jumped a wire from the battery and the blower motor works fine. The problem is that it’s a constant power.

Pull the blower resistor stack (circled) and look at the individual coils. It will be obvious if it is the problem:

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[84 Shorty]

Pull the blower resistor stack (circled) and look at the individual coils. It will be obvious if it is the problem:

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Wires were snipped from that not even going to anywhere. I will have to try and wire everything from the diagram

 

[chengny]

Go to the junkyard and get a set of OEM wiring/vacuum hose harnesses. The materials used to manufacture them will essentially last forever. I'd be surprised if they wanted anything more than $40 -$50. Then as a bonus, you can then sell that aftermarket junk on CL or ebay.

When you have the OEM harnesses in hand, just run each through the applicable grommet in the firewall.

On the engine side there are:

5 - plug-in connections to make at the various components (traced in red below). The compressor's power lead connector doesn't really count because it should come already made up to the harness (orange). I strongly doubt you still have a fast idle solenoid on the carburetor so I deleted it.

4 - ring terminal connections that need to be made (yellow trace). Actually there are only 3 because the blower relay and motor share a common ground screw next to the evap casing.

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In the cab you will only need to make 3 plug connections (in the blue boxes). Two of them connect at the back of the control panel - the blower speed switch & the mode select switch. The third one is just a short branch lead that connects to the fuse block and supplies power to the system. It is twisted with the mode select switch.

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That is it for the electrical harness.

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[84 Shorty]

Go to the junkyard and get a set of OEM wiring/vacuum hose harnesses. The materials used to manufacture them will essentially last forever. I'd be surprised if they wanted anything more than $40 -$50. Then as a bonus, you can then sell that aftermarket junk on CL or ebay.

When you have the OEM harnesses in hand, just run each through the applicable grommet in the firewall.

On the engine side there are:

5 - plug-in connections to make at the various components (traced in red below). The compressor's power lead connector doesn't really count because it should come already made up to the harness (orange). I strongly doubt you still have a fast idle solenoid on the carburetor so I deleted it.

4 - ring terminal connections that need to be made (yellow trace). Actually there are only 3 because the blower relay and motor share a common ground screw next to the evap casing.

You must be registered for see images attach

In the cab you will only need to make 3 plug connections (in the blue boxes). Two of them connect at the back of the control panel - the blower speed switch & the mode select switch. The third one is just a short branch lead that connects to the fuse block and supplies power to the system. It is twisted with the mode select switch.

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That is it for the electrical harness.

Thanks, what’s the green box?

 

[chengny]

Thanks, what’s the green box?

Oh sorry, Andrew. I just noticed that you haven't been here very long (only 17 posts).

Most folks learn quickly that - when it comes to color anyway - they should never listen to me. I am extremely red/green color deficient, almost color blind. Generally, when I write responses that require color descriptions of a marked up dwg, I have an RGB color table that I refer to. For example the decimal code for basic orange is (255,165,0). But last night it was late and I felt confident about which color on the palette was orange. So, deciding to go rogue, I chose the color on my own. Apparently that didn't work out too well.

Anyway, the connection shown within the green box is where the power supply to the A/C compressor clutch is branched off - from the main A/C harness. The splice is made at the firewall a few inches inboard of the FW junction block. The FW JB is where the red wire - which supplies power to the blower relay - is connected (circled in yellow).

 

[84 Shorty]

Oh sorry, Andrew. I just noticed that you haven't been here very long (only 17 posts).

Most folks learn quickly that - when it comes to color anyway - they should never listen to me. I am extremely red/green color deficient, almost color blind. Generally, when I write responses that require color descriptions of a marked up dwg, I have an RGB color table that I refer to. For example the decimal code for basic orange is (255,165,0). But last night it was late and I felt confident about which color on the palette was orange. So, deciding to go rogue, I chose the color on my own. Apparently that didn't work out too well.

Anyway, the connection shown within the green box is where the power supply to the A/C compressor clutch is branched off - from the main A/C harness. The splice is made at the firewall a few inches inboard of the FW junction block. The FW JB is where the red wire - which supplies power to the blower relay - is connected (circled in yellow).

Thanks, this is a big help. I called every junk yard in town. Only one had a 87 C10, couldn’t tell me what all was left on it. Going to have a look and see if the wiring is there. I’ll dive into this rats nest tomorrow and keep you posted.

 

[chengny]

The harness/switch connectors (as well as the color of the wires to the switch) shown above, are specific to a heat-only installation. The images were simply meant to show how the HVAC control system received power from the fuse block. That harness is actually from a 1987 with a non-AC system. Here is a heat-only harness from an earlier model:

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And here's what the socket on the harness side looks like:

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[chengny]

These might help you troubleshoot:

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[84 Shorty]

Here is the only brown pigtail I see close to the switch connector. I unplugged it to see if it was getting power with a test light, nothing. We called it a night, tomorrow we plan on running a jumper from the battery to the brown pigtail to see if it gets power

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[84 Shorty]

shout out to Chengny if this works tomorrow. He’s been incredibly helpful throughout this ordeal.

 

[chengny]

That's it. And, as we now know, the reason there's no power on that lead is probably because the HTR fuse isn't in place (or is blown):

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Also, I gave you bad information about the 25 A fuse in the AUX HTR A/C slot - it is not required. Unfused power to that bank is straight from the ignition switch on the IGN 3 terminal.

 

[84 Shorty]

Replaced the fuse still not getting power to controls. But getting power everywhere else. I’m tired of messing with it, looks like I’m taking it somewhere.

 

[Honky Kong jr]

Replaced the fuse still not getting power to controls. But getting power everywhere else. I’m tired of messing with it, looks like I’m taking it somewhere.

All they are gonna do is hack **** together to make it work and charge a **** ton of money, and you won’t know what they did if you ever have to mess with it. Might as well do it your self and fuse any power source that you add to insure you don’t burn your truck down.

 

[chengny]

All they are gonna do is hack **** together to make it work and charge a **** ton of money, and you won’t know what they did if you ever have to mess with it. Might as well do it your self and fuse any power source that you add to insure you don’t burn your truck down.

Really Andrew, 2X what HKJ says. You have dropped in a complete engine compartment harness, and spliced it into the cab harness the right way (i.e. by soldering/heat shrinking the connections). Then you proved that the entire system will work as designed - by supplying the control panel with an external power source. If you can do all that in one day, you can surely figure out why there is no power from the fuse block to the end of a single wire less than 3 feet away.

If you don't want to tear into your loom/fuse block, just run a new lead (again as HJK says, with an in-line fuse). Tap into the front of the block and run the wire straight over to the pigtail on the mode control harness plug. Use the ACC switched power jack adjacent to the radio fuse. It will be wired exactly the same (schematically speaking) as if you were using the factory wiring and the blocked mounted HTR fuse:

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