My 1970 Sedan DeVille. I can't get my AC to cool the car.

[chrisntam]

Hi Stuart,

This is the condenser that Scot installed in my '70.  He said it was bolt-in, no mods:

https://www.ebay.com/itm/234017485989

Bernie

To tag onto Stu's post, why (if it is) is this one better than the factory condenser?

[V63]

It's actually pretty 'cool' !
it's the modern technology of high efficiency parallel flow,
but mounts like the original without fabrication.
This technology removes heat better.
More efficient. Lighter weight too.

[bctexas]

To tag onto Stu's post, why (if it is) is this one better than the factory condenser?

Hi Chris,

Actually, Scot installed the parallel flow condenser for me just before he shipped the car to me.  He said it made a small difference, but he didn't have a lot of time to evaluate it.  And it came to me that way so I cannot attest to the improvement.

To build on what V63 said, the old style condenser was two fairly large copper tubes that ran back and forth with vertical aluminum fins to dissipate heat.  It was sufficient for R-12.  The parallel flow condenser has multiple thin, horizontal, flat aluminum tubes that run between "tanks".  Plus the fins are more densely packed than the old style condenser.  It has much more surface area for the refrigerant and airflow to contact, and dissipates heat more efficiently.  The pics are from my '65 with the original condenser and the '70 with the parallel flow.

I'm pretty convinced that the final piece of the puzzle is the compressor.  Next spring when the weather warms up again I'm going to switch to a modern replacement.  I've read of several examples of systems like mine but with a modern compressor that can get the temperature drop that we cannot achieve with the factory R6 running R-134a.

Happy Motoring!

[Scot Minesinger]

One of my friends with a 1969 Cadillac rode in Bernie's 1970 SDV with the improved condenser and my 1970 DVC with the stock condenser and he had me switch to the modern parallel flow condenser.  He did the three items on my list and he is now happy even with a factory A6 compressor here in VA.  For PA the A6 compressor with r134 should be fine, for TX maybe not and a modern one might be better.

[scotth3886]

Can the parallel flow condenser be used with R12?

[V63]

Absolutely!

[scotth3886]

Absolutely!

My otherwise original system had been converted for 134 by the previous owner in Scottsdale and didn't work worth a chit.  Even here on a 90s something day I couldn't get more than a 30 degree drop from ambient to interior vent temp in a triple black car.  I can't even imagine what this would have been like in Scottsdale.

I replaced the vacuum pans under the passenger side dash and the drivers' side airbox and  that resulted in about 4x the airflow and 20+ drop in temps by converting back to R12. Now it works like these did when I worked for a dealer when these were new cars.  However, given that my system is all original, I imagine that I'll have some work to do one of these days and new condenser could well be part of it.   

[V63]

I'm starting to believe that cycling the compressor is a bad idea, so I'm putting that on a definite hold.
Do you guys still recommend getting the more efficient condenser? Obviously I've got to solve the purge door sealing issue too. I would estimate it is sealing about 85%  but I could still feel cold air leaking out.

Cadillac (GM) themselves agreed to 'cycle' the A6 in 1977 and 1978 🤦🏻‍♂️, and it's now an industry standard. We had one new and I have owned several since...excellent AC system and compressor failures just not at issue.

I had a 1987 Rolls Royce and guess what,  they were still Cycling the GM A6, at $200k list price.

So the 'sky is falling' with cycling an A6 does not resound too loudly.

The A6 was so heavy... Cadillac (GM Harrison)   was engineering a new lighter weight aluminum compressor 'designed' to cycle 🙄✅ called the R4  introduced for 1979, they were plagued with problems and embarrassing premature failure.

The problem today with using a 'rebuilt' A6 is getting one that's not junk. I was forced to give up there and started buying the NEW aluminum A6 with great results.

["Cadillac Kid" Greg Surfas 15364]

Just a note here.  With the orifice tube type expansion device as used post 1976, the pressures in the system would equalize very rapidly when the compressor cycled off, so that when the A-6 did restart it was doing so essentially "unloaded" .
Greg Surfas

[Scot Minesinger]

Never seen a good compressor cycling conversion from constant running to cycling that worked.  Yes if the factory did it, then the chances of success are much higher.  Changing a constant running compressor designed by the factory to cycling because it worked in other years is not logical - don't do it.

I repair ac systems and have to assume responsibility for function.  Would never go this way because in the last two month friends brought me two compressor cycling systems which did not function at all that were original constant running.  Converted back to constant running and no issues, nice cooling - even at 90+'F.

Always best to bring the car to a qualified entity and state the problem and let them own the solution.  If you tell a repair entity how to fix it and it does not work then you enjoy some ownership in the failure.  When customers tell me how to fix their system, not always but usually, I do not relay on their advice.

[V63]

I converted my own 1968 convertible for use during HORRIFIC heat 110+, ironically in Scottsdale, it did have a rebuilt A6 with discharge in the 30's. I also eliminated the engine cooling clutch fan to a flex fan. I added a manual water valve in the heater circuit for only anticipated use, this eliminates a source of heat from proximity of the AC absorption. So yes, seeing is believing, and I accept ownership of pleasing results.

[scotth3886]

I converted my own 1968 convertible for use during HORRIFIC heat 110+, ironically in Scottsdale, it did have a rebuilt A6 with discharge in the 30's. I also eliminated the engine cooling clutch fan to a flex fan. I added a manual water valve in the heater circuit for only anticipated use, this eliminates a source of heat from proximity of the AC absorption. So yes, seeing is believing, and I accept ownership of pleasing results.

My blend door vacuum pan had a pinhole leak that would only allow the door to close about halfway so at least half of the floor was coming out the floor vents.  Replacing that plus returning to R12 resulted in this (pic).  Although, with triple black, if the car has been heat soaked in the sun for a while, it still take 5 mins or so for the interior to become comfortable, but the outlet vent temps are down under 40 in a couple of minutes. 

[V63]

That's the elephant in the room using readily available 134 the entire system was not designed for.

I also stepped up my 1968 steel blower Squirrel cage to about 1/3 larger plastic version. it did take some fabrication, but improved the velocity nicely. 

[stushug]

Here we go guys, thanks to one of Scot's posts in another thread, I got the heater core box out of the car. I would have taken a long time to find those four screws on the inside if not for that post! They were much easier to remove than I thought, except that I dropped both bolts from the passenger side. They must have fallen behind the carpet so I'll have to find them. That said, I'm NOT looking forward to getting them back in. I took some pictures, the best I could, of the passenger side so anyone can see where they're located. I circled the bolts in red. The ones on the driver side are in the same locations, a mirror of the passenger side. Anyway, the purge door was missing 95% of the sealing material so now I know why air was still leaking into the engine compartment. I took that apart and sandblasted it so now it's ready for new foam. I checked the actuator for the purge door and it is working fine.
The rubber seal on the blend door has become a bit flimsy and misshapened over years and looks like it can't seal completely. The corners are cupped and the long edge is pretty weak. You can see light pouring through in the pics. I know I can buy new foam but I'm not sure about the rubber seal.
The heater core and evaporator core are both in fine shape so I'll be leaving them alone.

Where can I source new foam and maybe something to fix the rubber flap on the blend door?

[bctexas]

V63 said: "The problem today with using a 'rebuilt' A6 is getting one that's not junk. I was forced to give up there and started buying the NEW aluminum A6 with great results."

Can you share exactly which make and model of aluminum A6 you used?  Also, are you indeed running R-134a?  I'm not 100% sure from your messages.

Thanks!  This is a great thread.

[stushug]

V63 said: "The problem today with using a 'rebuilt' A6 is getting one that's not junk. I was forced to give up there and started buying the NEW aluminum A6 with great results."

That's exactly why I chose to send mine in and have it rebuilt. I knew I was starting with a good core that was just in need of refreshing.

[stushug]

Anyone know where I can get new foam to seal my purge door that will survive underhood conditions?

[V63]

V63 said: "The problem today with using a 'rebuilt' A6 is getting one that's not junk. I was forced to give up there and started buying the NEW aluminum A6 with great results."

Can you share exactly which make and model of aluminum A6 you used?  Also, are you indeed running R-134a?  I'm not 100% sure from your messages.

Thanks!  This is a great thread.

I just shopped for a unit that looked like this, the Cadillac clutch and belt spacing is unique and despite ordering one for a Cadillac I always get the Chevrolet . I do not believe they offer one for Cadillac. So the compressor mounting needs to be fabricated to align the belts. I sourced mine from a local auto parts chain.

[V63]

Anyone know where I can get new foam to seal my purge door that will survive underhood conditions?

They do offer a self adhesive black foam used to seal camper shells that's about a 1/4 think?
Maybe check the window sealing area of a home improvement store. Much of the foam offered in the 60's was a true foam rubber and while it was super soft it would crystallize vs poly foams today that do not. Upholstery supply? Auto weatherstrip?

Might Use 3m weatherstrip adhesive for best results

[bctexas]

Anyone know where I can get new foam to seal my purge door that will survive underhood conditions?

Perhaps a call to Steele Rubber Products.  You will want something that can stand exposure to the engine compartment.....