leesvet

Thats a very good explaination and probable...knowing that these thin wall evap cores run upwards of 400 psi....that makes perfect sense. Block 400 psi with a compressor behind it and I can see an internal weld ripping apart.

SunCr

I'm a little lost - is someone confusing an Evaporator with the Condenser? Your gages never hit anything outside of the normal range on the Low and if it backed up to 400 in the Evaporator, it would have long since blown a hole in the hood on the High (and if you were standing over it, you wouldn't be posting now). Static pressures rarely get much higher than 100 psi. The high side is engineered to average 200 psi.
The high side cutout is 400 and the pressure relief spews at 600. The Low Pressure Contacts are closed at 50 and it's downhill from there. I think you unnecessarily sliced up a good Evaporator, but I'm not there looking at it.

VetteMed

High side was running around 190-200, low side 25-45 as it cycled.

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 running from the center, to the exit tube/suction line

myk7

I believe that restricter plate should have had a tube welded to it and exited out the evap through the first part of the evap,then the accumulator hose attached to it. Did your accumulator hose connection tube just stop there where it entered the evap?

I'll cut mine open sometime this weekend.

VetteMed

Yes, a tube would have allowed the refrigerant to flow only down in the "first" half, then up in the second half, and then out through the tube. I didn't remove anything internal to the evap, only cut off the external tubing leading to the accumulator hose.

myk7

Here's my upper section. It appears yours wasn't assembled with all the parts.

SunCr

Wow - Factoryaire brand or one from the Discounters? I'd take it back and get another one. I've had horrible luck with aftermarket compressors - some labeled new - but never an Evaporator. I've never had a problem returning broken a/c stuff and getting a replacement plus gas & oil and I suppose if I yelled loud enough I'd probably gotten another Accumulator for their screwup.

VetteMed

I have contacted the ebay seller I got it from, he is going to check with the supplier but it sounds like I'll be able to get a replacement. Myk7, thanks a million for the pics of your evap, I may need to use them to show the seller what is missing in the unit I have. At least now we have a concrete diagnosis for what was wrong with the system.

VetteMed

SIGH... I just received a new evaporator, it's a "ready-aire" unit, brand-new, and I looked inside the evaporator outlet pipe, and I can see the ridges in the end tank area - meaning that there is no tube as referenced above. Could I really have received 2 defective evaporators, a year apart? Or is there some piece of this puzzle that's missing?

myk7

Before I cut mine open, I looked inside the exit tube. I too could see ridges and couldn't really tell how far the tube went in. It went in farther than it appeared it did from outside. I'd suggest running a bent wire or something down it and see how long it is.

VetteMed

I just ran a bent wire type tool in there, and the tube stops immediately as it meets the end of the core. I'm certain of it. I can see the plate mid-way down the core, where the tube should have continued to, but it doesn't.

myk7

I wouldn't use it. If it just like your other one, I can't see how it would possibly work. I wish I hadn't installed my new one already.. oh well

leesvet

I seriously do not think that tube makes a difference...
the gas flows inward and expands thru the entire core...not necessarily flowing like you'd think. All it has to do if fill the core and collect heat. As heat is picked up its carried out. The goal is to disperse the gas...not direct it so much. I see why the tube in the middle might make some sense...to dump the gas in the center for a more uniform dispersal but its not that important. Its still going to move thru the core regardless of where its dumped in. Look at the core like a balloon, not like a million pathways. The veins, channels, all that 'area' is for heat transfer, contact area, not for the gas to travel.

Besides, the odds of getting 2 defective parts weeks apart, in a market that mfgs thousands of these units...? slim to none.

Al Borman

Your compressor should not be cycling on/off so rapidly. For the most part it should be on for long durations, and cycle off for shorter durations. This cycling will be governed by your AC cutoff switch, which switches the compressor on/off depending on low pressure range(a full R12 or R134a charge is a must). Personally I think you have a defective cutoff switch, or a whacked out compressor. With all these rapid cycles, the compressor can not really perform its job correctly. That compressor cannot suck/push properly if it is going on/off so dang much, no rocket science with this concept. Also, on your compressor there are 2 lines. The one going to the accumulator should be very cold to touch, and the one that goes to the condensor should be very warm to the touch. I think the problem at your evaporator is just a byproduct of the compressor not operating properly. The oil collection in your evap. is probably caused by the weak overall system flow due to rapid compressor cycling. Anyway, listen to what SunCr says, he is the resident AC expert as far back as I can remember....

VetteMed

I agree, I am tempted to not use it either -- but now 2 separate vendors have shipped the same item to me, probably from the same factory - how could nobody else have had problems with these units? Can you cut the bottom out of your core to see if there's a difference there?

VetteMed

But.... the refrigerant is going to go in the path of least resistance, like any other fluid or gas. That would be to enter at the bottom-front of the core, run straight up the first plate, hit the top of the core, then go straight out to the suction from the compressor.

It's that first straight-up plate that causes my concern - the bottom "tank" of the core never fills with refrigerant, and there is no reason why refrigerant would go straight up to the top and go towards a blind end, rather than just getting sucked out the suction line.

VetteMed

TO restate more simply - there's no logical way the refrigerant can ever fill the core when the path of least resistance is to exit immediately out the suction line.

Al Borman

I am not trying to take this thread in a completely different direction, but are you not concerned about the rapid cycling of your compressor ? Have you tried shorting your compressor cut-off switch so that the compressor runs continuously, while monitoring your Low and High side readings ? Also, are you confident that you fully charged with 36ozs of R12 ? That Low side reading of 26psi is a bit low(but accuracy of gauges could also come into play here).......At any rate, I do like the evap. cut-away pics !!! I have never seen one cut open like that !!!

myk7

I agree.. why run that first inlet tube right up by the exit tube? It would work better to just let it run in the bottom and make it's way up to the exit tube. But still, I believe the design with the long exit tube is the best/right one.

I'll cut the bottom out of mine in a minute, but I expect it to be just like yours.

VetteMed

I appreciate your concern regarding the cycling. I did in fact jump the pressure switch, to make the compressor stay on - the suction line iced up but the evap never got cold other than the first plate where the refrigerant flows straight upwards from the bottom. I took the car to a shop at that point - to let a "pro" take a look - they were not the brightest bulbs on the tree, but they have been doing AC for a long time, and were scratching their heads. They suggested adding another 12 oz, which I did. No change. They then suggested that the variable orifice tube might be the problem - so they evac'd the refrigerant (removed 2.25 lbs at that point, which is the factory spec), we swapped in a standard O-tube, and recharged with 2.25 lbs. No difference.