Need some help with my A/C PLEASE

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AK49BWL

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In the trucks that applies to, the compressor relay was directly activated by the HVAC controller, and there was only one pressure switch on the low side for cycling. The high pressure switch indeed activated the recirc door. With the Vortec and later, the PCM assumes control over the compressor cycling, therefore there is no need for the high pressure switch to deal with the recirc.

Not only that, but on trucks that the high pressure switch actuated the recirc door, there was no button in the HVAC controller to actuate it yourself. I'd be hard pressed to find a 95+ controller that doesn't have the dedicated Recirc switch lol


Yeah that manual is referring to the 88-94 systems, note it talking about the blower fan relayS... There's only one in the newer models for the high blower speed.
 

east302

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In the trucks that applies to, the compressor relay was directly activated by the HVAC controller, and there was only one pressure switch on the low side for cycling. The high pressure switch indeed activated the recirc door. With the Vortec and later, the PCM assumes control over the compressor cycling, therefore there is no need for the high pressure switch to deal with the recirc.

Not only that, but on trucks that the high pressure switch actuated the recirc door, there was no button in the HVAC controller to actuate it yourself. I'd be hard pressed to find a 95+ controller that doesn't have the dedicated Recirc switch lol

Hmm, seems redundant then. Any idea what it does? Mines a 98 and has that second switch at the hose manifold plus the recirc button.
 

Bigred81

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In the trucks that applies to, the compressor relay was directly activated by the HVAC controller, and there was only one pressure switch on the low side for cycling. The high pressure switch indeed activated the recirc door. With the Vortec and later, the PCM assumes control over the compressor cycling, therefore there is no need for the high pressure switch to deal with the recirc.

Not only that, but on trucks that the high pressure switch actuated the recirc door, there was no button in the HVAC controller to actuate it yourself. I'd be hard pressed to find a 95+ controller that doesn't have the dedicated Recirc switch lol


Yeah that manual is referring to the 88-94 systems, note it talking about the blower fan relayS... There's only one in the newer models for the high blower speed.
Ok. Bought the switch. I have to take it in and get the freon taken out then I’ll install new switch. However! I did just jump all three switches and the ac will still not engage. I can still jump it from the relay so it does work. The AC butting still doesn’t light up and also I’ve read the defrost button engages the ac clutch but that isn’t doing it either. I’m ready to burn this beast.
 

AK49BWL

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Hmm, seems redundant then. Any idea what it does? Mines a 98 and has that second switch at the hose manifold plus the recirc button.
I'd be guessing at best right now without looking at the two high pressure switch cutoff pressure values, but I think the one inline with the A/C switch cuts out at a higher pressure than the one in the compressor, to keep the system from even activating at the PCM level until the pressure comes down to an acceptable level.
 

SUBURBAN5

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I would remove the cap (slowly if you like) and see what were talking about. It should be like a tire. Unless you screw it slowly or missing an o ring it should thread in fast and seal. If you feel better discharging it I understand for piece of mine.. just trying to save the hassle
 

AK49BWL

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Ok. Bought the switch. I have to take it in and get the freon taken out then I’ll install new switch. However! I did just jump all three switches and the ac will still not engage. I can still jump it from the relay so it does work. The AC butting still doesn’t light up and also I’ve read the defrost button engages the ac clutch but that isn’t doing it either. I’m ready to burn this beast.
In that case, I'd have to look at the traces on the HVAC controller board. Chances are, one is burned if the button doesn't even light up. Which means you'll need another new controller....sorry!

As for the switches still not engaging the relay, I'm slightly stumped. You jumped all three individually and it still didn't work? That would imply an issue at the PCM... OR, the ground point for the two pressure switches. AARRGH I'm an idiot. It's not going to work if the controller is not sending the signal to turn on the A/C.

You'd have to jump a 12v source to the dark green/white stripe wire (leave the light green wire alone) to send the "A/C Request" signal to the PCM, THEN, it may work.
 

SUBURBAN5

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As for the switches still not engaging the relay, I'm slightly stumped. You jumped all three individually and it still didn't work? That would imply an issue at the PCM... OR, the ground point for the two pressure switches. AARRGH I'm an idiot. It's not going to work if the controller is not sending the signal to turn on the A/C.

You'd have to jump a 12v source to the dark green/white stripe wire (leave the light green wire alone) to send the "A/C Request" signal to the PCM, THEN, it may work.

Man idk how you learned this but I got to hand it to you.. you seem like you know your sh**
 

east302

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Looks like the blower switch being “off” disables the a/c command? Could just be an issue with that then since he was having problems with the fan speed and the button LED isn’t coming on.

Wonder if there’s a way to test or disable that?

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