mike70t

my 2004 Silverado AC compressor sporadically shuts off...when it runs its ice cold...the min I go down the interstate it shuts off..the pressure is at 40 lbs...new cycle switch installed, a new AC blower/temp control was also installed...it runs cruising around town but sometime even then it will shut off..i did check the compressor and when AC is blowing hot the compressor is off...please help

bl89tbi

Did you get any help? If you did, what solved it?

My 2003 Silverado SS is OK according my AC repair shop. System is full, compressor working, switch working, relay working, fuse working. But it does not deliver cold air. AC guy says it's probably one temperature sensor in the front, in the cabin or elsewhere acting up and not giving a go ahead signal to the AC system. How does one find the source of that problem?
I don't even know where to begin looking, neither did he.

mike70t

Mine was the compressor...so many things can go wrong..urs may be the blend door. Il

tech2

if the compressor is turning on, the pcm is not inhibiting a.c function.
if you have cold air at start up and then it blows warm later, its can be a bad compressor...trying reving the engine up to 2500 rpm and holding it there for 20 seconds...if cold air returns...the compressor is tired or the refrigerant level is low.

-if you have zero cold air...feel the a.c lines going into the fire wall...the high side (small diameter line) should be hot and the low side (large line) should be cold. If you have this, I would check the temp blend door and make sure the actuator is moving through it range.

if the lines have no diff in temperature the problem is not with the air distribution system.

bl89tbi

I have checked some.
The compressor gets a start signal from the relay.
It starts and goes for about 2-5 seconds.
I can see the compressor turning.
Something tells it to go off. It's almost like I can hear a sparkle inte relay.
10 seconds later it tries again.
Repeat ad infinitum.

If I force run the compressor the thin tube becomes cold.
But no cold air reaches the cabin.
I have tried activating every possible inlet to the cabin, no cold.

Is this where revving up to 2500 rpm may tell if the compressor is worn out?
How do I get to to the temp blend door, check it, activate it?

tech2

on off every 10 seconds; its short cycling from low refrigerant levels....the system has a leak. find and repair the leak...charge the system and you should be good.


if no cold air is reaching the cabin...you may have a blend door that is faulty in the hvac case. find the temp blend door actuator. engine running....move the temp blend **** and see if acutator moves the temp blend door.

bl89tbi

That sounds like good advice, tech2. Only, I don't know where to look for the blend door actuator.
The blend ****, is that what I thought was temperature setting? It goes from blue to red and show a number, degrees temperature.

In the old days, when the blend **** was a lever that pulled a cable and thus activated the blend door, I might have figured it out.

ARFFAZ

Blend door replace

ARFFAZ

Get under there and move the temp settings to see if the actuator moves

Also try removing your HVAC/ECAS fuse for a few minutes. It is located in the engine compartment fuse panel.

bl89tbi

Thanks ARFFAZ! Apologies for delay!
Got it out last night. NOT as easy as video shows. All the volts needed through connector, no movement. Will pick it apart before ordering new.