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AC Issues with 1970 Sedan Deville

Started by jsnassar, June 27, 2015, 12:14:27 PM

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jsnassar

Hi all,

I truly enjoy the posts here.  You all have been very helpful thus far in my journey.

I am having some AC problems that are driving me crazy.  Now, I am no AC expert, but can usually figure things out.

The climate control system seems to work fine...All blowers/actuators seem to be operate.  Here is the problem:  When I start the car in the morning (or first time in the day) it blows cold  - 50/55 degrees or so.  As the engine heats up, the AC temp rises and I can't get it below 70 degrees.

I thought that the heater control valve might be stuck open - but tested it and that's not it. 

Had new AC hoses and lines installed 2 weeks ago by a pro and recharged.  The lines do begin to sweat as the temp rises.

I ordered Cadillac Tim's book but haven't received it yet. 

Any thoughts?  I am in South Louisiana and NEED AC to drive it during theses hot summer days.


Thanks in advance,

Joey

Scot Minesinger

This is a difficult one to diagnose over the internet, and I have three 1970 Cadillacs where I have restored the climate control systems, so here goes:

1.  Get the tools they are not expensive and generally the purchase of them is about the cost of one trip to the mechanic.  They are at a minimum that you can buy at e-bay, HD or auto parts store (buy good quality):

a.  Set of gauges, Robin air gauge set and hoses (if you are r12 or r134, make sure you have right connections)
b.  Shop manual and Cadillac Tim's climate control book (Google Cadillac Tim in Iva, SC) his book saves you major time.
c.  Multi meter (Fluke is recommended)  This reads volts DC, and ohms minimum ,amps would be good too
d.  Vacuum pump (usually sold for brake bleeding, but it tests vacuum actuators)

2.  Your climate control system fails in the a/c mode, so if you lost climate controls a/c would come on.  Disconnect the vacuum line from the power servo, plug it, and your system will be in full a/c.  If system cools fine, then you know problem is likely in dash unit or vacuum lines. 

3.  If air is not blowing cold but your a/c is on, look at compressor clutch, is it engaged and spinning? 

4.  If clutch is spinning put your fingers on the metal part of the hoses that connect to back of compressor, your are feeling for a temperature difference, the fatter line should be cold, like a glass full of ice water, and the thinner line should be hot, almost uncomfortable to touch.  If that is happening your refrigeration circuit is probably OK.

5.  If refrigeration circuit is OK, power servo is OK, and air is coming out dash, now we are into a quagmire.

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

jsnassar

Thanks for your quick reply. 

Before I started this post, I think I read every single one of your posts on the 1970 climate control system.

I tried everything you said...Most of which I had already tried, but I thought I would give it another once-over.

Clutch engaging.  Lines correct temp to touch. Vacuum line to power servo disconnected and plugged.

I even tried bypassing the heater lines altogether to rule out a faulty valve.

The problem is this:

AC blows really cold when the engine is cold and parked - goes down to 50-55 degrees as it should. As soon as I drive it, the temperature rises immediately.  It is 95 degrees in south Louisiana and about 90% humidity. The air output rises to a constant temp of 70 degrees.  Lots of water is dripping from the evaporator as it should.

Could there be a door opening somewhere and mixing hot air in?  Could the evaporator be freezing up?

I really want to try and figure this out without bringing it in to a shop, but I am at the extent of my knowledge on the subject.

Thanks again.

"Cadillac Kid" Greg Surfas 15364

Joey,
If your system has been charged with R-134a, 65 or 70 is all you are going to get, same as here in Southern Texas.
If your system is still using R12 and is not modified I would recommend a factory service manual for your year. It contains a comprehensive explanation of the system an an excellent diagnosis proceedure.
Greg Surfas
PS Scott missed you in Milwaulke
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-

jsnassar

Thanks Greg. 

It is R12 and not modified.  I am just baffled because it blows cold first then gets hot later.  I will get a manual.  Haven't needed it yet.  Bought the car about a year ago, and has been great up until now. 

I didn't even know I had a problem until it got really hot here.  :)


"Cadillac Kid" Greg Surfas 15364

Joey,
With your system on and running, check the site glass for bubbles or foam. If you find that chances are that you are short of refrigerant. If the site glass is clear and the suction line warms up your POA might be stickey, or you might have some moisture in your system. An accurate diagnosis must be made with knowledge of the pressures and temperatures involved (via gages and thermometers).
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-

Scot Minesinger

I have three teenagers, one in college and another starting in August - no money issue, just demanding on my time.  Then my day job (I'm self employed) was crushing me, yes over worked and over paid.  Anyway you get the idea - no time.  So just could not swing GN2015, I so wanted to be there, but it would have been a bad idea.  Had signed up and all but had to cancel.  Just hired a new employee just so can work less hours.  Let's hope it works out and I can attend GN2016 in LV.

Anyway on to your problem:

1.  You need to put a set of gauges on the car and see what is going on.
2.  Need to buy the manuals, the factory shop manual and Tim's book.  Tim's book is not going to help you I don't think this time, but it will in the future.
3.  It is like Greg wrote, reads like you have a refrigeration problem.

OK, one last thing to try that I have never posted before.  The 69 and 70 Cadillacs have a pancake style damper actuator in addition to the power servo on the firewall.  This decides whether air goes in the cabin or in the engine bay.  This is a don't blow air on old ladies ankles delay thing.  When car is not warmed up for example air blows into engine bay, and then when the car is warmed up air blows into cabin.  If the actuator is bad (test it with vacuum pump) unfortunately air will blow into engine bay.  You will see kind of a triangle shaped discharge.  Put your hand there and see if the air blows out of there into engine bay and if it is cold.  I wired mine so it can only blow into cabin, because that damper actuator is prone to failure with all the heat.  The car also had a temp switch behind alternator for this purpose, so it seemed kind of dumb.

If you cannot find engine bay climate control discharge and your controls work, then remove servo vacuum line and plug.  Tee a manifold vacuum line and connect to power servo so it gets full vacuum (heat).  The with car cold (not warmed up, so 100'F is OK), put climate control on and start car with hood open and feel for the air flow right below power servo.  Once you have located it you can see if cold air comes out when you put the system back to normal.

Keep plugging away like me out of necessity you will become a 1970 climate control repair technician.  After repairing 1966, 1967, 1968, 1970, 1972, 1974, and 1976 climate controls, I say 1970 is the most difficult.  The worst is a molested dash where an audio tech has been in there.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Jeff Rosansky CLC #28373

Ibassume you are getting good airflow?  That will determine if the doors are messed up or if the coil is icing over. You can disconnect the power servo and manually wire the blend door open to the stop and see if that makes a difference. If so then you need to determine if it is just out of rig or if the car sensors think you are too cool.
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

"Cadillac Kid" Greg Surfas 15364

Scott sounds like your business is taking off. Just wondered because you were registered and there were som great cars there.
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-

mgbeda

I'm no expert, but it sounds to me like your AC evaporator is freezing up in the high humidity.  Once it gets coated with ice it won't cool near as efficiently.  If you turn just the AC off (car still going) for a few minutes and then start the AC again, does it come cold again?

-mB
-Mike Beda
CLC #24610
1976 Sedan DeVille (Bessie)

jsnassar

#10
Scot,  Purge door IS staying open and blowing air into the engine compartment at all times.  Still getting air flow into the cabin, though.  How do you access the door to wire it shut as you did?  Can this be done without ripping everything apart?

Mike, I thought that would be the case, but even after the car sits a while (45 minutes or so) AC Sill blows 70 degrees.

I'm going through Tim's book now in hopes of finding a solution.

Scot Minesinger

Joey,

I tried to photograph how I had the purge door closed to the cabin and just won't work well unless I jack it up and get the lights out.  If it comes to that let me know and I will.  Look down where the throttle lever that is connected to gas pedal penetrates the firewall and you will see a bracket with two bolts.  You remove one of those bolts.  Then get a piece of 1/2" or 3/4" x 1/8" steel strap maybe 18" long or so (you will need to cut it to fit).  Drill a hole in one end of the strap that will accommodate the bolt you just removed.

Feel up in the purge opening and you will see that you can press the flapper towards the car interior and air will all go into the cabin.  Put a good bend in that strap such that when the bolt is inserted in the hole of the strap and back into the bracket, the door will be held closed so air can purge.  Then tighten the bolt and you are done.


Greg,

Yes I was register and my business is going well.  There was just no way I could go.  Hopefully I get that all resolved for next April.  Nothing is free.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

jsnassar

Scot, thanks for all of your help.

I got the purge door wired shut, and airflow has improved dramatically.  The actuator was leaking and i guess it was opened part way.

Still having cooling problems, so I guess I will have to bring it to my mechanic friend who knows ac - its got to be the compressor getting less efficient when it heats up or the POA or expansion valve. 


Scot Minesinger

Joey,

If the two metal refrigeration pipes connected to back of compressor that transition to rubber hoses do not have a temperature differential then it is most likely refrigeration related.  The fatter line should feel 40;F or so like a cold drink of water with ice in it, and the narrow line should be uncomfortably hot to touch, like 150'F or so.  Although this is not an acid test, it does establish a problem if the temperatures are not what they should be on an 80'F day.

You may want to get a set of gauges to be sure, easy to buy on e-bay (get Robinaire or other good brand) and takes about 15 minutes to read them. 

Unfortunately these climate controls often fail with multiple issues and sound like you got a few of them squared away.  Now that you have the purge door wired to direct air to cabin, you should plug vacuum hose feeding the actuator, as it is likely just leaking (cut a piece of 1/8 round metal stock 1" long, cut vacuum line 2" from end and join the 2" piece back with the 1/8" round stock, then re-attach - looks authentic, but no leak.

Please let us know the results.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Scot Minesinger

Another thought:

This has happened to me numerous times, but have not written about it before - rodents.

They can build a nest inside the evap casing that ruins heat transfer (keeps heat in car from going to refrigerant and making air cold leaving evap casing) but does not compromise air flow that much.  You need a snake camera to check this, and this is a good tool to have anyway, couple hundred on Griotts or other places.  Remove blower and you should easily be able to see with snake camera.  There are metal air flow vanes between blower and evap to make sure evap is evenly coated with air flow, so you cannot get your hand in there to feel.  Unfortunately they usually build their nest on the other side of evap.  You can hole saw a 1" cut for inspection on the other side of the casing and make a sheet metal patch to see if this happened. 

Also look to see if the rubber condensate drain is underneath on the evaporator casing (need to get under car to see).  Picture of this is attached on a 67, which is similar.  If this is missing or severely compromised, it is likely mice are in there.  They sell these at USA Parts for reasonable price.

If mice got in there and built a nest, you may be able to clean it through the inspection hole somewhat, and see if there is an improvement.  Either way that casing is going to have to be removed and cleaned, then re-installed.  If this is the case, most mechanics in my area use a sledge hammer and bust off 75% of the attaching bolt holes, so I would do this myself.  Get the system evacuated, then perform your careful repair work and get it recharged.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty