Harrison AC Evaporator Box Sticker

[Mark E.]

The top photo below is the remnants of the sticker that was on the evaporator box of my 1970.
The second photo is a reproduction for sale on eBay.

In the lower right corner, I can read "SAE-AIR-60" which matches the reproduction.

But I can't read what was in the lower left corner. Is "EBA-70-70B" on the repro "correct"?
Repros with different years are available.

And what do these characters mean?

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AC System Update:

You can probably tell from my other threads that I'm up to my eyeballs restoring the AC system. The inside half of the evaporator box is removed, along with all other under hood components. The vacuum system and controls work, and the doors seem to move like they should. The seal along the blend door which is visible with the evaporator removed looks remarkably good. So I don't think I need to tear into the box under the dash. My plan right now:

- Compressor: Probably original so decided to have Dom restore it.

- Condenser: Probably original, and "worked when parked" 28 years ago, and kept sealed since. I had it flushed and pressure checked and intend to reuse it.

- Evaporator: It also worked when parked and was going to use it. But the guys at Carr's Corvette said it's hard to flush them out because of their "parallel design". They also touted that new evaporators are more efficient. So I'm leaning towards replacing it with new.

- POA: Again, worked when parked. But they are notorious for acting up, so I'm leaning towards finding an NOS. Carr's Corvette, Old Air Products, and Vintage Air all recommend a POA replacement kit which cycles the compressor on/off. Even though that's less expensive than an NOS POA, I hesitant to have my original A6 cycling. Is the clutch designed to do that? Plus it won't look original.

- Expansion Valve: I can get a new replacement for under $50, or spend several hundred on NOS, if I can find one, or clean mine up and test it. To be safe and look original, I'm leaning towards NOS.

- Manifold, hoses, drier: All new. Probably not exactly like the original (crimps, drier top, etc.) but close.

I have a small inventory of R12, so I plan to use it. I hear it's more efficient than R134 too, but worry about the impact to the ozone layer.

[Larry M.]

Re: Harrison AC Evaporator Box Sticker

POA valves can be tested. They can also be rebuilt. I would install old tested or NOS POA for your new system. But that's just me........

I might also clean, test , and reuse the old evaporator. But that is very subjective. Not certain if new made overseas is better than cleaned and tested made in USA.

The current replacement AC DELCO driers are essentially the same as original for 1968 and later cars. Driers can also be rebuilt and look and perform as new.

Larry

[Michael B.]

Re: Harrison AC Evaporator Box Sticker

Mark,

The POA valves usually fail because the system was contaminated, most often with a compressor failure. If your system was working in the past, I'd bet the POA valve is OK. You can bench test it yourself if you have a set of refrigeration gauges. I'll attach a link with instructions. The POA valve maintains a constant pressure inside the evaporator, 29.5 psi for R12. When they fail it's usually in the full open position. If it's working properly when you apply air for the test no air will be exiting the valve until you reach 29.5 psi then you'll hear a pop as the valve opens. Then even as you increase air pressure going into the valve it will still maintain 29.5 psi.

I have never heard the old evaporators were not as efficient as the replacements. I'd be interested in learning more about that if you have any information.

As far as the impact on the environment using R12, there is none if done properly. The only negative impact in the past was when technicians released the R12 directly into the atmosphere when servicing the system; a common practice back then. And yes, R12 is a better choice for a C2 or C3 corvette. R134a is a great refrigerant in a system designed for it, but it operates at higher pressures and temperatures on the high side, meaning more heat has to be dissipated at the condenser. That means a larger, or more efficient condenser than the ones we have. I have no official source to quote but I've been told that you'll lose about 20% efficiency in a C3 switching to R134a. In a cool climate that probably wouldn't be a problem, but in Dallas you would cook.

https://www.chevelles.com/forums/32-heating-cooling/1046913-poa-valve-testing.html

Good Luck,

Mike

[Mark E.]

Re: Harrison AC Evaporator Box Sticker

Thanks Mike; it's good to hear from you.

I just sourced an NOS POA, PN 5910593 on eBay. To be safe, I'll test it. Maybe my old POA is fine, but for me the extra $ for NOS is worth it if it reduces the chance of failure. The last thing I want after charging the system is to discover a bad part.

Old Air Products claims their new evaporators are more efficient because there's more tube surface area. Again, to be safe, I plan to get a new one. Carr's Corvette strongly recommended a new evaporator because they said flushing isn't effective due to their "parallel construction". I believe all this means is the core has parallel tubes which connect the end tanks. So if one tube is blocked or dirty, the flush just routes through another tube. I think Old Air said they manufacture them in the US, but I'll recheck that.

[Michael B.]

Re: Harrison AC Evaporator Box Sticker

Mark,

I'm going to give Old Air a call tomorrow. I was borderline on replacing my evaporator anyway as I have some deep scoring in one of the tubes where a fitting has rubbed. It's easy to replace now that the car is apart, and if a new one is more efficient that makes the case.

Another thing you might consider is replacing the blower motor with one for an 84 corvette. The squirrel cage on the 84 is bigger, and has a different curvature to the blades resulting in about a 25% increase in air movement. Michael Davis wrote a book titled "Air Conditioning Strategies for the 63-82 Corvette" in which he recommended this conversion. You'll have to fabricate a 3/4 inch spacer to go between the new blower motor and the evaporator housing. Now is the time to do that considering it's out of the car. Rock Auto sells the blower and fan together for $62.79 (part #1580213). You'll also need a new vent tube. Rock Auto sells one that works well for around four bucks (part #75769). I did this to one of my cars and it made a big difference.

I made the spacer from a black plastic cutting board from Walmart. The board was 3/8" think so I doubled it over on itself to get the 3/4 inches needed. I put construction adhesive between the layers, then made a pattern on cardboard for the spacer. Send me your address on PM if you would like me to send you the pattern; it will save you a lot of time.

The only downside is that it won't appear 100% original with that spacer installed, but since the blower sits underneath the passenger side fender someone would have to look awfully hard to see it. It was a terrific trade off for increased comfort.

Mike

[Mark E.]

Re: Harrison AC Evaporator Box Sticker

Thanks Mike.

I was aware of the 84 blower mod (is that the only C4 blower which works?). I didn't plan to do this for a couple reasons:

- As I recall (it's been a few months) air flow with the original blower was adequate. Not great, but ok.
- The way I work (at most a few hours a week, if the weather is nice, and if I feel like it) a project like this may add weeks to downtime.

I may do this, but after the AC is back together. I did not remove the right side of the evaporator housing which is the half with the blower. So access to the blower isn't much better than fully assembled. For pre-'73 cars, the blower is right there when the fender grille removed.

Meanwhile, I will PM my address. I'd like your spacer template for this possible future project.

[Mathew S.]

Re: Harrison AC Evaporator Box Sticker

Mark, I have had both the POA, drier, condenser, and expansion valve redone by Original Air in Florida (https://originalair.com/). The POA was redone to with with R134a, and tigers were redone to ensure they worked. I have pieces of the original manifold hose to the compressor as well, in my garage. The system blows well, and comes out stronger fro the ball vents than the center dash with the original fan.

All hoses but one are reproduction ones as is the evaporator and compressor. It’s not as cold as the AC in my 95, but was comfy coming back from the Corvette Invasion.

[Mark E.]

Re: Harrison AC Evaporator Box Sticker

Mark, I have had both the POA, drier, condenser, and expansion valve redone by Original Air in Florida (https://originalair.com/). The POA was redone to with with R134a, and tigers were redone to ensure they worked. I have pieces of the original manifold hose to the compressor as well, in my garage. The system blows well, and comes out stronger fro the ball vents than the center dash with the original fan.

All hoses but one are reproduction ones as is the evaporator and compressor. It’s not as cold as the AC in my 95, but was comfy coming back from the Corvette Invasion.

Mathew,

My original hoses are hard as a rock, so I'm replacing all of them.

And having the tigers redone always makes a big difference.

[Michael B.]

Re: Harrison AC Evaporator Box Sticker

Mark,

The 84 blower motor is still a single wire motor. Sometime later (I'm not sure what year) they changed to a two wire motor. Those motors still work but you'll need to purchase a special pigtail to connect it. The 84 is "Plug and Play".

Mike

[Mark E.]

Re: Harrison AC Evaporator Box Sticker

Thanks Mike.

[Jeff W.]

Re: Harrison AC Evaporator Box Sticker

Mark, did you ever get an answer to your label code question? My evaporator had a pristine label on the evaporator inside the case. Does yours? Mine disappeared during boil out. Here is a close up from my 1968. I have no idea what those numbers mean.
.

[Jeff W.]

Re: Harrison AC Evaporator Box Sticker

And here is the one from the outside of the case. I never realized before now that the numbers on the left are different between the two.