I seem to be having problems with my ac system, it has freon in it. When i turn on to max ac its barely blowing cold air.

 

Is it blowing air but just warm or is it blowing cold air but only at a slow speed?

 

it seems to be blowing at a slow speed and when it is on. An when it is off it seem to be blowing hot air. Even tho the heater part isn't even on.

 

Does it have the Computer (automatic) Climate Control or the manual control?

Regarding the fan speed, if it has the manual, there will be a blower motor resistor block that is part of the fan speed control circuit. If it is the automatic type, there is a solid state blower motor speed module. Either of these can fail.

Then regarding the temperature control, there is what is called the "blend door actuator" that is electronically controlled. Both systems have these but they parts differ slightly.

Finally, there can be issues with the vacuum hoses in the engine compartment that supply vacuum to the actuators for the HVAC system that control to where the air blows.

Look for threads on all these topics to help you better identify the origin of the problem and then the solution.

 

I have to manually control it. if i replace the blower motor resistor, it should go back to blowing ac colder? if i replace that and it still isnt working then its the vacuum lines for the hvac system.

 

I forgot to ask, when you direct the HVAC system to be in AC mode, does the clutch on the AC compressor engage and make the compressor rotate? If the compressor come on, does the accumulator (the good-sized aluminum can) get cold to the touch? If so, your AC system is working fine and the problem is with getting the cold air delivered to the passenger compartment.

The primary way by which the cold air can be prevented from getting to the passenger compartment is that the "blend-door-actuator", basically an electronically controlled damper, has broken and the door is stuck in the full-heat position. This happened to me and is not an uncommon problems.

The blend-door actuator can be tested by doing the following: With the engine warmed up and at operating temperature and the HVAC system off, set the controls for full heat. It is probably easiest to check the temperature by directing the air flow to the defrost vents or the dash vents. Note the temperature. It should be very warm. Then change the temperature control to full cool but with the AC system off. If the light comes on for it, override it and turn it off. If the temperature of the air blowing out of the ducts warms up to close to the outside air, the blend door actuator is working correctly.

Depending on the year, there is a way to stick your hand under the dash through the glove-box opening and feel the blend-door actuator moving. This is best described by searching for videos on replacing the blend door actuator.

Now, regarding the blower motor speed: The blower motor resistors are part of the circuit that controls the fan speed. This circuit is independent of the vacuum controlled HVAC actuators and electronically controlled blend-door actuator that controls the temperature (hot and cold). The failure mechanism for blower motor speed on a manual system does not affect whether or not the AC system is working or if the cold air can get to the passenger compartment. The blower-motor speed control only controls whether or not the fan is on and at what speed.

A failure of the vacuum system (i.e. a vacuum leak) will disable the actuators that direct to where the air is to flow in the the rest of the HVAC plenum (duct) system with the result that the air comes out in the wrong place; e.g. the defrost ducts instead of the heater ducts. There is one vacuum actuator that also participates in the directing of the air through or bypassing the heater core but a failure of it (by not enough vacuum or the actuator has failed) will only have a partial effect on the temperature. Search Google for the manual HVAC diagram for your year Blazer and you'll see what I'm talking about regarding the vacuum and blend door actuators.

 

The aluminum can does get cold to the touch, it sweats as well when it gets cold. sounds like its the blend door actuator is not closed all the way. sometime it gets hot in the cabin as well. i dont know if its because its got a flowmaster on it as well or its the ac system not being closed all the way.

 

Yes, it sounds like the blend-door actuator could be the main fault. Look up videos on Youtube to see how to check and replace it.

If you are desperate, you can remove the blower motor control resistors and manually move the blend-door.


The red circled area is where your blower motor control resistors are located. Looking down into this opening will show you the blend door.




This is the view looking down into through where the access port/blower motor resistors are mounted. The arrow indicates the blend door and its axle is the straight line in yellow. The grill to the right of the blend-door is the heater core. Here, the blend door is in the full hot position.

 

Thanks for the help. I will check this stuff out today when it gets a little bit cooler outside. I might do it manually just to get some ac in thr cabin. I will replace it tho.

 

Sounds like a blend door issue. I had full time heat for a while. That is not good in Mississippi! I was able to replace the actuator from the passenger footwell without much disassembly at all, but I had to get a thumb ratchet to screw the bolt out of the old one and into the new one.