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

Started by stushug, October 11, 2021, 03:38:16 PM

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stushug

This has been an ongoing project, starting a few years ago. I purchased the car 8/3/2021 knowing that the AC did not work. Knowing nothing about the system, I had it "converted" to 134a. It blew slightly cool air, nothing close to what was needed to cool the car. Since then, I've worked with Classic Auto Air in Tampa and Cadillac Tim. I've rebuilt or replaced almost every part over the years. The in dash unit is working perfectly, and the dial is calibrated to temperature. All of the inside temp sensors are well within spec. I rebuilt the power servo and replaced the rotary vacuum switch with a working one from Tim. All of the vacuum lines are good, and everything functions as they should. The last piece was having the compressor rebuilt by Classic. I also replaced the old expansion valve, drier and bought one of their POA valves calibrated for 134a. I had them make me all new hoses too, to avoid the leaks I had with the old non-barrier hoses. I had a local AC shop do the final install of the hoses, expansion valve and charging of the system. The problem is that no matter what, the coolest temp we can get out of the dash vents is about 60F. My service guy has been doing this for many years and I trust that he is well versed. He pinched of the heater hoses to make sure there was no hot coolant going to the heater core for a test. He told me that all of the pressures are correct, and the pipes that are supposed to get hot get hot and the pipes that are supposed to get cold are cold. I've spoken with Classic and they confirm the numbers he's given me as far as the charge amount, and High and Low pressure readings are consistent with a correctly working system. My local guy suggested that I check the blend door operation and I've confirmed that the blend door that moves with the arm from the power servo is moving to the correct positions in relation to heating or cooling. My local guy also used a sniffer for leakage and found none. The entire system was purged of all the old refrigerant and oil before the system was finally charged. It was also vacuumed down.
I'm not sure what else I can check, I am hoping someone else has gone through this and found an answer for their car.

Scot Minesinger

How about a picture of the POA valve "calibrated to r134", it is not stock or one that cycles, that could be an issue.  What temperature was it outside when it was blowing 60'F air inside?  What City and State do you live and drive your Cadillac?

Presuming it is OK, here are the things you can do to make it work better:

1.  Replace the condenser with a higher capacity parallel flow unit.  They make them and sell them on e-bay for about $250 (same mounting and does not change charge of 134).  If you want a real original look, maybe a 1974 -76 Cadillac condenser, as they are more capacity.

2.  The climate control for 1969-70 used a crappy method of "warm-up", where to prevent cold air in winter from blowing on your ankles the conditioned air dumps into the engine bay right below the actuator that moves the damper.  Trouble is the seals fail over time, and I have found that sometimes 50% of the air flow (or 50% of the cooling) dumps into the engine bay when the actuator is good and the seal is bad.  You can feel for yourself - easy to check.  It is not as bad in heating because air flows less restricted out of the lower heating vents and the capacity is so great, even lower heating capacity will be very effective.

3.  Make sure your fan is operating correctly.  Connect battery voltage right to the fan and if no improvement in air flow, then the fan is good.  And you may be able to purchase a higher airflow fan/motor combo which would also increase cooling.

The disadvantage of using r12 is of course it is expensive, few garages have it, and it is very difficult to recover, filter and re-use.  The advantage of r134 (used from 1994 thru 2014 - thereabouts), is that probably 300 million cars were  made to use and the average age of a used car is 15 years or so, accordingly it is low cost and everyone still uses it.  However, of course that will change, and then it may make sense to just use r12.

Good luck,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

Stuart,
At this point with the information you have given us some assumptions must be made to help.

Assumptions: The P.O.A was adjusted to maintain a minimum of 36PSIG. The expansion valve you installed is calibrated for refrigerant 134a. ALL the Mineral oil was flushed (with solvent) from the system.

If the above assumptions are correct AND the vent discharge temperature is 60 degrees with the car at highway speed(stabilized for 15 minutes) then there is something wrong with one or more of the refrigeration system components, regardless what has been said.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

stushug

Greg,
I worked directly with Classic Auto Air on this and they sold me the POA valve knowing it had to be calibrated for 134a. I purchased the expansion valve from them also with them knowing that it is a 134a system. They rebuilt the compressor knowing the car and that it has a 134a setup. I flushed the condenser with solvent myself and I told my local guy that the rest of the system, which would only be the evaporator coil needed flushed (everything else is new, hoses, POA valve, expansion valve), so I assume he did that.

Scot,
1. I can get an new condenser, no problem.

QuoteTrouble is the seals fail over time, and I have found that sometimes 50% of the air flow (or 50% of the cooling) dumps into the engine bay when the actuator is good and the seal is bad.  You can feel for yourself - easy to check.  It is not as bad in heating because air flows less restricted out of the lower heating vents and the capacity is so great, even lower heating capacity will be very effective.

2. I know about the delay in the climate system until the coolant reaches about 120 F. I checked operation of the blend door and it moves freely like it's supposed to but I couldn't confirm that the seal is still good. I'm assuming that you mean the door that is controlled by the power servo. I attached a picture with the pivot circled. If I need to replace that seal, what is the least complicated way to get to that door? It seems to me that it is a lot of work to get to it and the engine block is in the way.
BTW, my local tech had also mentioned the problem with the blend door causing me to lose as much as 10 F if it is not sealing properly.

3. The fan is working properly. All speeds are working and the air flow itself is great.

The ambient temps were high 70's and low 80's when I was getting these results. I live in Pittsburgh PA.
I have also included a pic of the POA valve.

V63

Been there done all that...got the T shirt 🤦🏻‍♂️✅.

I have been circumventing the STV POA and VIR!
just did a 63 (STV) today. Blowing 35-40 degrees at vent. I utilize the modern parallel flow (High efficiency) condensors.

We must remember that AC systems remove heat thru the condensor.
Further, engine temperature and air flow extremely important.... I do NOT trust Radiator clutch fans opting instead for 'flex fans'  (street use rating not noisy race use)

R 134 is NOT as efficient as 12 and it was improved condensor technology that increased its effectiveness.


"Cadillac Kid" Greg Surfas 15364

Although it is not a Kosher diagnostic tool I might suggest putting a manual shut off in the heater water line and shutting the water flow off completely. If this makes a difference in the discharge air temperature when you are calling for Max cooling then you have narrowed the problem down.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

stushug

Quote from: V63 on October 11, 2021, 10:33:05 PM
Been there done all that...got the T shirt 🤦🏻‍♂️✅.

I have been circumventing the STV POA and VIR!
just did a 63 (STV) today. Blowing 35-40 degrees at vent. I utilize the modern parallel flow (High efficiency) condensors.

We must remember that AC systems remove heat thru the condensor.
Further, engine temperature and air flow extremely important.... I do NOT trust Radiator clutch fans opting instead for 'flex fans'  (street use rating not noisy race use)

R 134 is NOT as efficient as 12 and it was improved condensor technology that increased its effectiveness.

I used one of the flex fans you mention years ago in another car and it worked great to keep the coolant temps low, so I understand that perfectly!
I'm looking into a new condenser, can you recommend a source? How do you circumvent the STV POA and VIR?
I'm thinking that the seal on my blend door is pretty well shot, how hard is it to get to?

bctexas

Stuart,

The device Scot referred to is not the blend door.  It is what the service manual refers to as the "purge door".  On the ac casing, below and to the drivers side of the ac power servo is a vacuum actuator mounted vertically.  If you turn the key on without starting the engine, the fan should come on.  Stick your hand down behind the driver's side cylinder head below the purge door actuator.  You will feel all the air coming from the blower coming out of the purge door into the engine compartment.  That is the door that Scot is referring to.  Once the system is running, that purge door should close and seal.

I only know this because I learned it from Scot!

I'm not quite sure why they designed the delayed start this way.  They wired the fan to run any time the key is on, even if the ac is off, then they dump the air into the engine compartment until the ac is turned on.  My '65 uses a vacuum operated switch to power the fan, and the system doesn't start the fan until the proper time.  Makes more sense to me.....

Happy Motoring!
1965 CDV
1970 SDV

V63

Quote from: stushug on October 12, 2021, 10:12:45 AM
I used one of the flex fans you mention years ago in another car and it worked great to keep the coolant temps low, so I understand that perfectly!
I'm looking into a new condenser, can you recommend a source? How do you circumvent the STV POA and VIR?
I'm thinking that the seal on my blend door is pretty well shot, how hard is it to get to?

They make kits to eliminate the POA, (your system uses POA in 1970)  I used one on my 1968. I would start there.

The condensor you try and find a new one by size, just try to get it as large as your original one. You can search for 'universal' versions.
I remove the original side brackets And fabricate them to the new condensor. The new condensor is much thinner (and lighter). Strategize position more to the passenger side where connections are needed. Effectively I fabricated the new assembly to mount Exactly like the original. You will need a hose made for the lower condensor fitting as the original has tubing coming up.
It's not difficult project...but does require fabrication.

"Cadillac Kid" Greg Surfas 15364

Stuart
By your initial post you have thrown everything but the kitchen sink at this system. Once more I would respectfully suggest you isolate the refrigeration system be shutting g off the water to the heater coil. Then regardless of the blend door position you will be
Getting nothing but cooling. If the temperature is still above say 50 degrees while at highway cruise then your issue is somewhere in the refrigeration cycle.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

stushug

Quote from: "Cadillac Kid"  Greg Surfas 15364 on October 12, 2021, 12:11:07 PM
Stuart
By your initial post you have thrown everything but the kitchen sink at this system. Once more I would respectfully suggest you isolate the refrigeration system be shutting g off the water to the heater coil. Then regardless of the blend door position you will be
Getting nothing but cooling. If the temperature is still above say 50 degrees while at highway cruise then your issue is somewhere in the refrigeration cycle.
Greg Surfas
Greg,
I wasn't ignoring your suggestion, but I had mentioned in an earlier post that the shop that finalized the installation and charging had pinched off the the hoses going to the heater core and he said there was no difference. I think he did that with the car idling at about 1500 rpm though, not driving. I will try your suggestion to see what I get.

"Cadillac Kid" Greg Surfas 15364

In order to get any amount of rel cooling the engine and thus the AC compressor has to be at higher speed than idle.  The A-6 has a capacity of 27,000 BTUH at 2000 RPM. About 1/4 of that at idle speeds.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

stushug

I just got back from a highway test drive. Before I left though, I checked the purge door. It was wide open as it should be until the car warmed up. Then it closed but it does NOT seal. I just found the first problem! Before leaving I also pinched off the hoses leading to and from the heater core. On the highway, I measured temps at the vents at around 55 for the lowest reading. I moved the dial to 85 to make sure there was no hot coolant going to the heater core, and it only blew cool air.  I got off the highway and opened up the pinched hoses for the ride back to see if there would be any difference. The AC temps stayed the same (55) and the heat was hot. I think that eliminates a heater core problem. Thanks to Greg for reminding me to check that!
I measured my condenser and will be ordering a parallel flow unit and the POA eliminator. I like the idea of cycling the clutch anyway. I think it's much better than spinning the compressor 100% of the time.

chrisntam

Good to hear you're running it into a corner.   Greg is the man when it comes to a/c systems, among other things Cadillac. 

Regarding cycling of the A6, I'd read somewhere that compressor wasn't designed to be cycled (maybe read it here).  I suggest you research that a bit.  The only downside of it running all the time is more drag on the engine and less mpg.
1970 Deville Convertible 
Dallas, Texas

Scot Minesinger

#14
No way I agree with cycling the clutch!  The clutch was designed to spin the compressor 100% of the time.  If you cycle it, it will fail prematurely.  Use the factory POA to maintain suction pressure.

You have done everything so far, and there are few alternatives remaining so that is good.  You read the FSM and that is also good.  These are not supernatural and they can be fixed.  I just fixed a 76 Cadillac where the VIR (combo of exp valve/drier/POA) was replaced with "something modern and better" which did not work at all - replaced it back with VIR and it worked great.  Cadillac spent millions engineering these systems, and there are few that can just guess a better way.

Greg is right at 70-80'F, outside, 60'F inside is not that great, and it should be colder.  If it was 100'F outside then OK, maybe 60'F might be expected with r134 and standard components.  I trust mechanics as far as I can throw them, the proof is in the results - you are cooling down the air about 15'F (75'F ambient minus 60'F discharge), which is not air conditioning effectively, should be more like a 35-40'F temperature drop.  You suffer a refrigeration issue (or heat contamination via bad heater control valve), which you should isolate as Greg suggested by by passing the heater core (just add a connector and connect both heater core hoses together).  Once you have established that by-passing the heater core is not an issue, the refrigeration circuit is suspect.

I agree that 134 is not as good as 12, but no one ever complained about 134 in a 1970 Cadillac on a 75'F day.  In fact when my transducer failed and cc resulted in full cooling it got too cold inside with r134 in my 1970 Cadillac on an 80'F day.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

Stuart
The A6  compressor was NEVER designed to cycle. At highway speeds that would entail the compressor when off would try to start and accelerate to something like 4000rpm instantly. The result is broken valves and shortened life.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

stushug

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.

bctexas

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
1965 CDV
1970 SDV

stushug

Hey Bernie,

I was looking at that exact one earlier today. Did you notice a marked improvement from using that condenser?
I'll probably be ordering it tomorrow morning. Thanks!

Stu

stushug

I should also mention that the actuator for the purge door is working. When it was closed, I disconnect the vacuum line and the door opened. As soon as I re-attached the vacuum line the door closed as it should. That said, I still have to resolve its inability to seal completely.