AC/Recirculate not working (1 Viewer)

brockdeck

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96 FZJ80

Replaced climate control dash lights, hopped in the truck this morning to realize my AC/Compressor is not switching on. Checked out climate control and PCB looks good, no corrosion, switches work.

Checked fuses based off a few other threads, but honestly stumped. AC worked great yesterday.

Bulbs changed, no idea 💡 If there is a correlation.

Press AC button, clutch does not engage.

Heater/cooler relay replaced, all fuses in dash and engine bay regarding heater/blower fan good.

Air circulation/intake button does absolutely nothing.

I would place my money on something now being damaged in the climate control module, but need some tips if anybody else has had a similar issue.
 
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brockdeck

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Just swapped out cooler/blower relay and checked fuses. Nothing

Any thoughts? Anybody just have a climate control unit just stop working?
 

ppc

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The first rule of mechanical repairs and modifications....
If a problem occurs after a change then the first step is to either verify or reverse that change.
By "touching" other components you are just expanding the possible causes and increasing the difficulty of repair.
 

brockdeck

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The first rule of mechanical repairs and modifications....
If a problem occurs after a change then the first step is to either verify or reverse that change.
By "touching" other components you are just expanding the possible causes and increasing the difficulty of repair.

Well I’ve already been through the reverse process, so that’s why I am here. I think that’s how we all usually end up here, right

We drive 20+ year old trucks, the chances of something else coincidentally failing is extremely high. I’ve been through 15 years of threads and looking for advice.
 

ppc

M Go Blue
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You did not mention that you reversed the modifications. If you want help it is imperative you state what you've done completely and accurately.
 

brockdeck

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You did not mention that you reversed the modifications. If you want help it is imperative you state what you've done completely and accurately.

True.

Sooo, you have advice? Or no cigar? I changed out light bulbs, I would not call that a significant equipment modification. I am trying to troubleshoot.

Yes, I have an FSM. Yes, I’ve been reading it. No, I haven’t figured it out yet.
 

ppc

M Go Blue
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Again need to be precise.

When you pressed the A/C button did the bulb illuminate? Did you just press or press and hold the button.
You stated the "circulation/intake button does nothing", again any lights in either position, did you hold the button down? Was there any movement of air through the system? How did you determine that there was no change of the air input source?
What about the other buttons such as airflow direction to defroster, a/c vents or floor. Could those be changed and were there any lights on those buttons?
Same thing related to fan speed buttons?

Did you make sure any wiring harness plugs were fully seated, no bent pins, broken wires?
How far did you disassemble the control unit and did everything reassemble without forcing anything or otherwise tweaking any parts out of position?
 

brockdeck

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Again need to be precise.

When you pressed the A/C button did the bulb illuminate? Did you just press or press and hold the button.
You stated the "circulation/intake button does nothing", again any lights in either position, did you hold the button down? Was there any movement of air through the system? How did you determine that there was no change of the air input source?
What about the other buttons such as airflow direction to defroster, a/c vents or floor. Could those be changed and were there any lights on those buttons?
Same thing related to fan speed buttons?

Did you make sure any wiring harness plugs were fully seated, no bent pins, broken wires?
How far did you disassemble the control unit and did everything reassemble without forcing anything or otherwise tweaking any parts out of position?
Again need to be precise.

When you pressed the A/C button did the bulb illuminate? Did you just press or press and hold the button.
You stated the "circulation/intake button does nothing", again any lights in either position, did you hold the button down? Was there any movement of air through the system? How did you determine that there was no change of the air input source?
What about the other buttons such as airflow direction to defroster, a/c vents or floor. Could those be changed and were there any lights on those buttons?
Same thing related to fan speed buttons?

Did you make sure any wiring harness plugs were fully seated, no bent pins, broken wires?
How far did you disassemble the control unit and did everything reassemble without forcing anything or otherwise tweaking any parts out of position?

Sorry for not being clear.

All controls work for changing the position of airflow, defrost etc. I took the LED bulbs out when I put it back together. Fan speed controls also work. Switches for AC/recirculate do absolutely nothing when pressed down, but they switch properly.

All connections are seated properly, condition of wires from harness look good and everything is properly connected in the harness.

Taking apart the unit I was extremely careful to not force anything. I checked the backside of the board for corrosion after removing the top board with care to not disturb the flex connectors it is connected to. All solder joints on that look good. I have a long history of working with computers and circuit boards, so even more confused as to why function has been lost since all traces/capacitors etc look correct on the board. I never tore down the entire unit past that, with the exception of taking the top of the AC and recirculate switches of to ensure they are actually clicking the mechanical joints as they are supposed to. Nothing beyond this was disturbed. I popped the unit out, carefully replaced bulbs, about it back in and lost AC function.

My initial consideration is that something has happened to the unit beyond my knowledge. I’m looking into a replacement now, as everything else looks good regarding fuses/relays and my AC was working great 24 hours ago.

To be clear the blower motor is pushing air, airflow and everything else can be controlled, but I cannot get the compressor to switch on from the unit. I’m going to jump the compressor connection tomorrow to see if it properly switches on.

Thanks for the help
 

brockdeck

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Found an old thread regarding a totally corroded AC amplifier unit. Has anybody had this issue on a non auto AC unit? Also, does anybody know exactly where this unit is located on a 03/96 build? I noticed several different spots it could be. I will take a look at the truck again when I am off of work.
 

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