I've replaced the blower motor and wheel on my 81 with the C4 version. and I still don't have much air flow. So I think I have leaves blocking my evaporator. What is the easiest way to clean this out?

 

sawzall

Seriously, though - my DD had a problem with blower volume.
A guy at work clued me in. The evap was corroded and closed off.
No leaves - just aluminum oxide. He cut through his from the inside with a sawzall.

Since my compressor and condensor were both shot, too - I went at the evap
with a BF screwdriver from the inside. voila - blower works again.

So - maybe not a sawzall - but you might have to replace it.
You gotta take the cover off on the firewall to check it out.
Can you get your arm in there from the blower motor hole ?

I'm glad I don't have or need AC.

Good luck !! :seeya

 

Sir,

I would say the only manner to really effectively clean the evaporator fins is to open and separate the passengers side of the firewall case. Others may say you can blow it out, however 20 plus years of all manner of organic debris are sitting right against and inside those evaporator fins. If you removed the blower motor and hose off the inlet side of the evaporator, much of this matter would push farther into the fins. The 1” or so drain in the bottom of the case is small and really intended for water removal to help prevent freeze up.

Its sort of like a compost heap in there. All the leaves, seeds, twigs, insects and molds have been decaying into an organic paste. Fix it right and you won’t have to do it again. On C2 AC models there is a screen inside the evap case right on the evaporator with 4 plastic push pins that hold it in place. On C3 similar screens can be added to the evaporator and case. I patterned firewall screens and evaporator screens for my C2 & C3’s.

I have developed several AC tips that I have used over years of my involvement. Incidentally none require the substitution of blower motors, fans or freon alternatives. My 67 427 on a 95 degree day blows 38 degrees at the lower vents when measured with my Blue Point IR thermometer.

When you say that there is little air flow, that can also be due to the leakage of air behind the dash. The AC duct work, distributor and boxes needs to be properly sealed to prevent loss of flow, otherwise it’s like an exhaust pipe with holes in it.

Stay coooool. :D

Geoffrey Coenen
NCRS #2473
NCM Lifetime #105
Precision Valley Corvette Museum Charter Member #20 (I think)
Retired #1 56, 63, 67, 68, 68, 69, 75, 99 and I want more! :D
Wanted: 1969 L-89 conv (no project)

 

I agree with most of Doc Rebuild's points. The real test would be to put a manometer on the intake side and exiting side of the evaporator coil, and read the pressure drop, but that is overkill. I would say first make sure the whole duct system is sealed up and not just bypassing air through a bunch of blown duct gaskets. I assume you cleaned out the fanwheel when you changed the blower motor. The blades in the fanwheel are cupped, and if the cups collect dirt, the dirt takes on a flat shape and obviously won't "scoop" as much air. If your ducts are all sealed, and the fan wheel is clean and the fan motor is working, and you still are not getting any air volume, it's safe to assume the coil is plugged.

As the Doc mentioned, the best move would be to take the cover off the coil. I would say just replace it, but there are ways to get it clean. For sure clean out the entire box and maybe enlarge the drain holes so the same things don't collect there again right away.

 

Get a shop vac and a 4" piece of 3/4" heater hose. Duct tape the heater hose intot he end of the shop vac hose. Insert into the cowl opening that feeds the evap core. Move around gently to dislidge the leaves and debris without damaging the face of the evap core.
If this doesn't work, try the remove the blower motor and fan method described above. If that doesn't work, open the evap box and clean it up. If you have to open the box, you should go ahead and replace the evap core.