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Discussion Starter #1
I have factory AC in my 68 Fastback that has not worked for years and I am weighing whether to try to fix/replace the non-working parts (e.g., condenser, hoses, compressor, to start) or install a new complete kit. My understanding is that on the cabin side, the AC and heater functions are combined into one assembly, with both refrigerant lines for the AC and lines carrying antifreeze for the heater. Can someone please confirm this?

If I want to remove the AC/heater assembly in the cabin to test it and/or replace the evaporator core, this would require disconnecting both the refrigerant and antifreeze lines in the engine compartment. I just want to confirm that this means that so long as the AC/heater assembly is out of the car, I can't drive the car or even run the engine because the antifreeze hoses are disconnected -- is this correct?

If correct, is there anything I can do to address this so I can drive the car while I have the assembly out? Could I perhaps simply connect the two open antifreeze hoses together with some type of coupler to keep the antifreeze running through the engine? I don't really have the option to keep my Mustang in non-working order for very long, so keeping the assembly out for more than a few hours is problematic for me.

Any insights or advice would be appreciated.
 

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Yes that is correct. The simple solution is just loop the heater hosez back on themselves. But honestly I cant think of any reason to remove the interior side unless the heater core or the evaporator has a hole in it. I'd replace any missing seals/lines on the engine side, maybe update to a newer style compressor and have it pressue checked by an ac shop. If it passes, have them charge it.
 

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Compared to a normal mustang heater, yes they combined the two functions into one box.
Yes you have to disconnect everything including AC to get it out.
I covered the hole left with some lexan, but anything can cover the hole left by pulling the box.
The cowl vent goes into the unit on the passenger side.... so you will need to block the cowl, I did this with the Scott Drake ones.
My ac had come down some, so my cowl vent had not been sealed for a while.
Once I got the car sealed up, the windows quit whistling at me, that alone was worth pulling the unit.
I found my AC ducts did not want to let go, so are kinda torn up now.
I struggled with this for a while and finally decided to go Classic Auto Air.
I HATE their compressor mounts, so I ordered the mounts used in their compressor upgrade kit. Have no idea why they do no use those excellent mounts in their complete kit.
They also have a condenser that looks like it is a bolt on... do not think I will bother with that though, still it seems strange they have better parts but do not use them in their flagship kit.

I have the old AC boxes, can take picts if you want. If you are willing to come get them you can have them. (Dallas, Ft. Worth)
I finally decided the cleanup and reinforcing they might need (due to age) was not worth my trouble.

Lee
 

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Discussion Starter #4
Thanks for the replies. Is there anything that needs to change in the evaporator/heater assembly in order to complete the conversion to R-134?
 

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Discussion Starter #5
Lee, thanks for the offer. If I lived closer I would take you up on your offer to have a backup plan, but I'm about 1,500 miles away in Santa Monica, CA.
 

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The simple solution is just loop the heater hosez back on themselves...
You can just plug both hoses too, they don't need to loop back. The internal water passages continue to work just fine. Mater of fact, some Mustangs had a vacuum operated valve in one heater hose that shut off water flow when heat wasn't called for.
 

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Discussion Starter #7
Simply plugging them is a great suggestion as well. Thanks.

Can anyone confirm that nothing needs to change in a factory evaporator/heater assembly in order to complete the conversion to R-134?
 

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You should have no problem at all using the oem evaporator with 134. Update the compressor and a bigger condenser plus receiver/dryer, etc and you should be golden. Chances are good your evaporator is fine and possibly better than a new replacement anyway...
 

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Different but similar situation: I recently changed out my AC system to a modern. I gutted everything but the evaporator. My '66 OEM evaporator works just fine with R134A.
 

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Discussion Starter #10
Thanks 66#3, that is reassuring. Did you have to flush out the evaporator to make sure there was no R-12 left in it?

After leaning toward a complete kit, I'm now starting to lean in the direction of replacing the compressor, condenser, dryer and all of the hoses in the engine bay and seeing if it works with the evaporator as is. I'm leaning toward either restoring my existing York compressor for R134 or replacing it with a York aluminum repro. I don't know why, but I just don't like the idea of replacing it with the Sanden, even if it is superior tech. I guess I'm more old school than I thought.

On NPD website, I see only one condenser option. Should I be looking elsewhere? Why a bigger condenser?
 

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Class Auto Air sells improved evaporator cores and condensers that work better for R134, but yo7 can flush and reuse the stock ones just fine. You will have to renlace the hoses with Ones made from modern Materials or they will leak with R134.

I highly recommend you take the time to rebuild your A/C Evaporator box. The seals are likely shot and the last thing you want to do is go through the headaches of getting it all working only to have the heater core leak and spill boiling hot antifreeze all over your floor and passenger‘s feet. I tracked down all the parts used to build a stock system and added it to my 68. CAA helped me restore all the pieces.

CAA also offers an under hood upgrade kit with new hoses, a Sanden compressor and everything needed to switch to R134. If you don’t care about looking 100% stock, this is a great Upgrade.
 

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Discussion Starter #12
Thanks for the feedback, Flade. I do sort of care about looking stock -- otherwise I would get the Sanden kit.

As for the evaporator, I understand the logic in the scenario you painted but pulling and rebuilding that along with everything in the engine bay substantially increases the time and effort and busts my budget. I spoke with Original Air today -- getting the plenum box rebuild is $425 plus shipping and it will take 6-8 weeks. I have not had any issues with antifreeze leaks to date so I'm working under the assumption the heater core will continue to perform. And to your point, I am a bit concerned about potential leaks of refrigerant in the evaporator core, as that hasn't been tested in many years. However, wouldn't a vacuum test address that issue before I commit to fill it with refrigerant?

Ah, so many considerations. It's no wonder that I still haven't gotten this done...
 

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Unless you are bent on originality, switching to a Sanden-type compressor should be considered. Much smoother, and more efficient than the York or Tecumseh compressors. Both the AC and heater of the factory unit are superb. Properly set up, your car will be a deep freeze in warm weather, and toasty in the winter.
 

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Thanks for the feedback, Flade. I do sort of care about looking stock -- otherwise I would get the Sanden kit.

As for the evaporator, I understand the logic in the scenario you painted but pulling and rebuilding that along with everything in the engine bay substantially increases the time and effort and busts my budget. I spoke with Original Air today -- getting the plenum box rebuild is $425 plus shipping and it will take 6-8 weeks. I have not had any issues with antifreeze leaks to date so I'm working under the assumption the heater core will continue to perform. And to your point, I am a bit concerned about potential leaks of refrigerant in the evaporator core, as that hasn't been tested in many years. However, wouldn't a vacuum test address that issue before I commit to fill it with refrigerant?

Ah, so many considerations. It's no wonder that I still haven't gotten this done...
I wouldn’t worry about the evaporator core. It’s unlikely it will leak. The hoses are much more likely to a be a problem. I replaced all mine with the modern barrier hoses even though I am running R12. That way if I switch to R134 later I don’t have to change anything. I am a bit of a purest too. I went with a stock compressor as well.

759548
 

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Discussion Starter #15
I'm definitely getting all new hoses and strongly leaning toward York compressor over Sanden (I really prefer the original stock look.) Also I need to replace the condenser (one of the valves snapped off my original) so I'll probably replace the dryer as well.

Can anyone tell me if I need to replace my expansion valve at the firewall? I have received conflicting info on that.
 

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Discussion Starter #16
Flade, beautiful engine bay, by the way.
 

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Discussion Starter #17
Flade, is your compressor a restored original York or the aluminum repro that NPD and others sell? That is the look I want.
 

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Discussion Starter #18
Consolidating some of my prior questions along with some new ones...

Can I re-use my existing expansion valve?
Can I re-use my existing compressor valves?
What is the difference between integral A/C and factory A/C?
Is there any easy way to confirm that my existing York compressor has NOT already been converted to R-134? All along I have been assuming the current setup was for R-12, but I guess it's possible the PO did the conversion before the condenser failed.
 

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If your system has been retrofitted with 134a it should have adapters on the service fittings as the connection is different from r12. Someone could have removed the adapters after filling I guess but seems unlikely.

The reason for a bigger (or more efficient) condenser is 134a is not as efficient as r12 and can tend to not cool well on a hot day at the stoplight.
 

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Here's my 2 cents:

Can I re-use my existing expansion valve? If its tests ok, yes. However, the underhood upgrade kit from Classic Auto Air includes a new expansion valve.
Can I re-use my existing compressor valves? IIRC, the R12 valves are different from the R134a valves to avoid mistakenly recharging with the wrong refrigerant.
What is the difference between integral A/C and factory A/C? Integral A/C combines the A/C with the heat and defrost functions and shares the same duct work and controls. Factory A/C is installed at the factory. Prior to 1967, Mustang A/C was an underdash unit and not integral. Starting with model year 1967 all Mustangs with factory A/C were integral.
Is there any easy way to confirm that my existing York compressor has NOT already been converted to R-134? The compressor valves are visually different. Compare what you have with pics of known R134a compressor valves.
 
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