A/C blower

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m1970

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I have a 94 Chevy 1500 and my a/c blower motor has really started to blow alot less air. It sounds like its blowing hard but not much comes through the vents. Keeping in mind it has never been just real good, but better than now. I know a lot of the new trucks have much better blowers but I don't what would fit into mine. Does anyone have any suggestions as to what I can put in that would be better than what I have?
 

someotherguy

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A few possibilities, all are somewhat common.

1. Vent position actuator linkages may be gummed up. It's the one above the driver's side of the transmission hump; there's a couple sliding flat metal linkages that have a little lube on them from the factory and over the years it hardens up and also gets contaminated with fuzz and dust. Lay down some newspaper so you don't ruin your carpet and shoot the linkages with WD40, operate your vent position controls back and forth to "work" the linkages, clean off excess WD40 with paper towel and apply a little spray white lithium grease. Be gentle with these assemblies so you don't break them or pop them apart. This is what you're looking for:
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2. Vent position slider linkages may be broken. A peek at them will be kind of obvious. Missing springs, plastic ends, arms popped off the ends of the doors, etc.

3. Evaporator core fins plugged up with debris. This job is a bit more involved because reaching it is difficult without removing the dash and HVAC box from the firewall. You can do a reasonable job of cleaning it detailed in a thread somewhere here on the forum - in a nutshell though you're removing the blower motor, digging out as much debris as you can by hand from the housing, if you have a sneaky vacuum you can put it in there to try for the last remaining bits. Then spray foaming evaporator core cleaner in there, following the directions, and then flush the housing out with your garden hose. You're gonna make a mess so consider covering the floorboard with a garbage sack to route the water out of the truck.

To give you an idea of just how bad they can get.. the pine straw and debris isn't the real issue, but it's not helping. The real issue is all the dust in the system that sticks to the evaporator fins and turns into a cake of mud, restricting airflow.
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ALL airflow through the system must pass though the evaporator core regardless of temperature setting, so you need it clean. You can see in this pic the airflow from the fresh air inlet in the cab's wiper cowl area, as well as the recirculate air under the door where it draws in from the cab, into the blower housing - then passes right across the evaporator core, then onto the heater core, blend doorp, and vent position doors:
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Richard
 

m1970

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A few possibilities, all are somewhat common.

1. Vent position actuator linkages may be gummed up. It's the one above the driver's side of the transmission hump; there's a couple sliding flat metal linkages that have a little lube on them from the factory and over the years it hardens up and also gets contaminated with fuzz and dust. Lay down some newspaper so you don't ruin your carpet and shoot the linkages with WD40, operate your vent position controls back and forth to "work" the linkages, clean off excess WD40 with paper towel and apply a little spray white lithium grease. Be gentle with these assemblies so you don't break them or pop them apart. This is what you're looking for:
You must be registered for see images attach


2. Vent position slider linkages may be broken. A peek at them will be kind of obvious. Missing springs, plastic ends, arms popped off the ends of the doors, etc.

3. Evaporator core fins plugged up with debris. This job is a bit more involved because reaching it is difficult without removing the dash and HVAC box from the firewall. You can do a reasonable job of cleaning it detailed in a thread somewhere here on the forum - in a nutshell though you're removing the blower motor, digging out as much debris as you can by hand from the housing, if you have a sneaky vacuum you can put it in there to try for the last remaining bits. Then spray foaming evaporator core cleaner in there, following the directions, and then flush the housing out with your garden hose. You're gonna make a mess so consider covering the floorboard with a garbage sack to route the water out of the truck.

To give you an idea of just how bad they can get.. the pine straw and debris isn't the real issue, but it's not helping. The real issue is all the dust in the system that sticks to the evaporator fins and turns into a cake of mud, restricting airflow.
You must be registered for see images attach


ALL airflow through the system must pass though the evaporator core regardless of temperature setting, so you need it clean. You can see in this pic the airflow from the fresh air inlet in the cab's wiper cowl area, as well as the recirculate air under the door where it draws in from the cab, into the blower housing - then passes right across the evaporator core, then onto the heater core, blend doorp, and vent position doors:
You must be registered for see images attach


Richard
I will definitely check all of that out. Thanks for the advice!
 

someotherguy

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To be clear, I posted those pics of the evaporator core from an HVAC box I'd obviously removed and disassembled, included them for illustration purposes. As you can see the "neck" of the passage between the blower housing and the evaporator core is what makes it difficult to clean without total disassembly. Some patience and small hands can get it clean enough to work much better with the method I described without having to tear everything apart, just going through the opening after you've pulled the blower motor.

I'm kinda multitasking working on some other stuff so I may not have been 100% clear. You don't absolutely need to pull the dash and HVAC box to get some cleaning done in there.

Richard
 
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