[Timritchieblue]

New to Colorodo life. A/C was working good. I just bought truck. LSA swap, cleaning up some wiring .
And now my a/c won’t kick on? I tryed testing the fuses? Good, relay good. Jumped relay and A/C kicks on? So does that mean my HVAC control is bad?? Ho do I test?

 

[cart7881]

Okay, what you know. The compressor will operate. The A/C relay is good. Bypassing the relay will cause the compressor to operate. If the A/C was working good before you 'cleaned up' the wiring, maybe recheck that wiring.

You are missing either the power supply for the relay, which is the 15A IGN fuse, or the ground for the relay which is in the PCM.

The way the system works is that the HVAC Conrol Module sends a voltage signal to the BCM requesting compressor operation. The BCM looks at the evaporator temperature and if it is above freezing sends a Class 2 Serial Data message to the PCM to turn on the compressor. The PCM looks at engine coolant temp, engine speed and A/C system pressure. If good, the PCM grounds the control circuit for the compressor relay.

Bottom line. If you have power from the IGN fuse to the relay and you are certain the relay is good, there is either a wiring problem between the fuse box and the PCM, or an issue with the PCM. Unless the BCM and HVAC Module were mucked with during the swap, the problem is most likely somewhere in the engine compartment. Either a high system presssure or a low system pressure will prevent the compressor from operating.

 

[Timritchieblue]

Thanks, I’m glad people still post on forums.
I forgot to add I replaced the low pressure switch with no change.
How can I check A/C havoc system switch? If I pull A/C relay how to check if switch is working?

 

[cart7881]

Under the instrument panel, forward of the glove box, look for a connector mounted to the face of the A/C case. Black connector, 10 wires. Disconnect and probe the terminal for the Green wire with a White stripe in the male half of the connector. Meter or test light. Find a good ground in the area. With the key on and A/C selected you should get 10-12 volts.

That's the circuit from the HVAC Module logic board to the BCM. There is no direct connection from the switch. This is because the switch is not the only way the compressor operates. It will automatically turn on if the mode select knob is turned to defrost and then the light in the switch will not illuminate.

 

[Timritchieblue]

Thanks sir. I’ll try to mess with
It tomorrow. Truck is got some issues, but when finished correctly, it will be a blast, just so much to fix. Had truck 5 days, brakes, wheel hub, CV axle, and hours of cleaning up wiring.

 

[cart7881]

Okay. I do not usually pry into personal information and apologize for asking. What model year truck do you have?

 

[Timritchieblue]

2005

 

[cart7881]

Thanks. Keep us posted.

 

[n9cv]

I do not usually inject myself into Carrt's postings but Ihave a question on your AC. When you press the AC button and the fan is on, Is the AC light illuminated (on) inside the AC button? It the answer is "yes" then when the fan switch is turned all the way counter clockwise does the fan stop and the AC light go "OFF". It is the light going off that I am really questioning. If the answer is "NO" the light stays on, then you have a bad dround connection probably in the splice pack mounted behnd the air cleaner on the passenger side inside fender. I have seen this problem severakl times. If it did go off from turning the fan switch (not pressing the AC button), then you can ignre this entire posting.

 

[Timritchieblue]

I’m interested in getting this figured out. When I push the switch in, I get nothing? No light?
I did a lot of wire clean up by the mass air / passanger side of truck.

I seen a video of a guy testing the a/c havac system by pulling relay, and and testing the A/C clutch enhancement button.

 

[cart7881]

I do not usually inject myself into Carrt's postings but Ihave a question on your AC. When you press the AC button and the fan is on, Is the AC light illuminated (on) inside the AC button? It the answer is "yes" then when the fan switch is turned all the way counter clockwise does the fan stop and the AC light go "OFF". It is the light going off that I am really questioning. If the answer is "NO" the light stays on, then you have a bad dround connection probably in the splice pack mounted behnd the air cleaner on the passenger side inside fender. I have seen this problem severakl times. If it did go off from turning the fan switch (not pressing the AC button), then you can ignre this entire posting.

Thank you for the post. The more 'eyes' there are on the problem, the more likely that a solution will be found. One person posting can easily overlook obvious clues sometimes. The only advantage that I have is access to the Service Manuals and the past history on this site. Before I joined here I took the time to read every single post from the beginning. That was in 2011 and it took me a couple of months. Learned a lot.

 

[Timritchieblue]

Tore into the trucks wiring and found this?? Looks broken??

 

[cart7881]

Whatever it is, it does appear to be broken. Where, exactly, in the truck is that thing located?

 

[Timritchieblue]

Was mointed here??

 

[cart7881]

Sorry, still don't recognize it. Mounted to the A/C case? Can you see where the wires go? At this time it doesn't appear to be OEM. The wiring looks a bit wonky.

 

[Timritchieblue]

It’s no telling.. I’m sad, I bought this fruck, but she’s mine.. and I’ll get it figured out. I’m very picky about wiring. I solder everything. This truck is built on clip on wire taps. 😤

don’t ask what I had to pay..

Now we got that out of the way… anyone rode in a Boosted 4x4 6.2l Colorodo lately?? AND I SMILE JUST THINKING ABOUT IT.

 

[cart7881]

There is a fix for damn near anything. Did you check for voltage at that connector?

 

[macgyver915]

Tore into the trucks wiring and found this?? Looks broken?? View attachment 345655

Could that be one of the two under dash lights?

 

[nathanbakker6]

View attachment 345657 Was mointed here??

This is the foot well bulb socket. Looks like someone tapped into the power wire for it. 194 style bulb, if you choose to pry that broken bulb out and replace it.

 

[nathanbakker6]

As far as the AC issue goes, Do you have access to a OBD2 scanner to read any codes the AC system may be throwing?