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Is this a defective evaporator?

vettemed on Fri May 27, 2011 10:58 PM User is offline

Year: 1991
Make: Chevy
Model: Corvette ZR-1
Engine Size: 5.7
Refrigerant Type: R-12

I think this evaporator is missing something - I think there should be a tube in the top of the core, connecting the restrictor plate type area halfway down, with the output tube to the accumulator. This evaporator doesn't have any such tube. Does this look correct?


Outside of entrance to evap:


Cutaway view of inside of entry port:



Outside view of exit port to suction line:


Cutaway view of exit port:



Close up of location where I think there should be a tube welded to the center of the plate in halfway into the end of the core - separating the 2 halves of the evap, or something of that sort, rather than what appears to be a very subtle restrictor plate... of course, just a solid plate would render the core useless, but I don't see how this thing is supposed to function properly.

Dougflas on Sat May 28, 2011 8:41 AM User is offline

Yep, tube with fitting cut off

mk378 on Sat May 28, 2011 10:22 AM User is offline

This looks like it is a single-pass parallel flow design. Liquid from the inlet goes down through the end section and fills the bottom manifold, then rises into the tubes in each plate where it boils. The top manifold should contain mostly gas. The baffle in the center may be intended to keep any liquid in the top from sloshing back and forth. The outlet needs to be able to collect gas from all the sections for it to work.

Edited: Sat May 28, 2011 at 10:26 AM by mk378

vettemed on Sat May 28, 2011 7:45 PM User is offline

The problem is, the liquid refrigerant enters at the bottom, runs straight up the first tube, then fills the top manifold. The bottom manifold presumably never fills with refrigerant, nor does any other tube within the evap.

iceman2555 on Sun May 29, 2011 5:15 PM User is offlineView users profile

Re read the original post. The movement of lube into the evaporator is a classic example of the system being undercharged. There is insufficient amount of liquid (vapor) refrigerant exiting the accumulator to move lubricant back into the accumulator. All the lubricant that has been added to all the different locations has been 'stabilized' thru movement of refrigerant back to the evaporator. The accumulator is lacking lubricant for the same reason. All lubricants are moving thru the system with the flow of refrigerant. An undercharged system will produce the issues of this post and the first. There is no need for lubricant to be added to all the components as stated in the post...simply add lubricant to the compressor and accumulator...the system will stabilize and the lubricant. The accumulator is a storage location for lubricant....and if it is dry...as stated in your post....the compressor will fail due to lack of lubricant re supply.
The use of three cans (12 oz each) does not equal 36 oz of refrigerant in the vehicle. The cans almost always maintain a small amount of refrigerant and the manifold/hose assembly requires a certain amount of refrigerant to 'pre charge'. This probably equals an under charge of at least 4-6 oz. To insure correct lubricant movement, the system must be totally charged. Pressures and an assumption of how much refrigerant was charged from numerous cans is not an acceptable method to insure correct charge rates.
Refrigerant should be added to the system utilizing the correct recharge equipment to weight or determine by flow how much refrigerant is in the system.



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