Air vent issue

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98chevy2500SS

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This is weird... For some reason, when I'm using A/C, the vents will randomly shut off. Sometimes it takes 20-30 minutes, sometimes 10 minutes, etc. The blower motor is still running and A/C compressor is on, but for some reason air won't come out of the vents after a while of driving. When I have the A/C OFF, with just outside air coming in, the vents work perfectly. I have lubed up the actuator, and made sure it is still working. Anybody have a clue as to what's happening with this? To get the vents to start blowing again, I have to flip around with the switch and then it will start blowing again. I should mention it does NOT default to defrost when this happens. I am at a loss of what could be the issue. Hopefully that all made sense..

Edit: truck is a 1997 Chevy K1500.
 
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SUBURBAN5

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Whenever my vents were acting wierd it ended up being a wiring issue behind the module. Heated up so bad the harness was melting
 

AK49BWL

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Yeah, kinda sounds like wiring or the control module, not the actuators. The modules are known to use inadequate transistors for load switching, and you probably have one about to fail.
 

98chevy2500SS

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Thanks guys. I had a brand new spare control module laying around in the garage, so I threw that in this afternoon. Hopefully that fixes it. If not, I'll probably have to diagnose further or just deal with it.
 

SUBURBAN5

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Thanks guys. I had a brand new spare control module laying around in the garage, so I threw that in this afternoon. Hopefully that fixes it. If not, I'll probably have to diagnose further or just deal with it.


When you take out the control module look at the wiring harness for melted wires. These are notorious for this issue
 

98chevy2500SS

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Evaporator core freezing up, maybe?
Not sure on that, when I switched to the floor vent for around 10 seconds, then flipped back to the front forward vents, it starts to work again so I don't think it would be that.

When you take out the control module look at the wiring harness for melted wires. These are notorious for this issue
Thankfully no melted wires. :waytogo:
 
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