A/C diagnosis help needed - 1970 Deville

[chrisntam]

Sorry for the long post.

Finally got around to putting the gauges on and got readings.  Did the Cooling Capacity Performance Test as outlined in the FSM.  First, a little background.

In '14, when I got the car, I put in a new evaporator, flushed the condenser, new expansion valve, rebuilt STV valve (Old Air Products out of Florida), rebuilt A6 (Old Air Products - Ft. Worth), original hoses.  Had a local shop put it all together, suck it down and charge it with R-12.  I put in the correct amount of oil.  Never really did cool like I thought it should and the front seal of the compressor leaked.

Fast forward to Spring of '18, I bought a new Four Seasons A6, I put the correct amount of oil in it, installed it, sucked it down and put in 4 cans of R12.  Never really cooled like I thought it should and it freezes up (as I found out when I drove to the San Marcos GN.

Fall of '18, I took it to a local shop that still works on R12 systems, they saw no issues w/ it except the two O-rings on the back of the compressor were leaking.  They replaced them, sucked it down and charged it with 4 cans of R12.

Still not cooling like it should, foam or bubbles in the site glass and freezing up.  Prior to the Louisville GN, I put in another can of R12, thinking the charge was low based on foam/bubbles in the site glass.  No difference.  Still freezing up, sometimes it would cool (50*) for about 15 minutes, once it cooled for about 45 minutes.  Then it starts blowing warm (70*+).

On the return trip from the '19 GN, I just ran the a/c for about 50 miles from the house, pulled in, popped the hood, the STV was froze, the return line coming to the compressor was froze and the evap connection to the exp valve was frozen.  See pics.

I ran the test twice today. It did not freeze up today.  Pics of the freeze up is after running it the last 50 miles coming home from the GN.

1st test it was 92 degrees, 60% RH, after 10 minutes of running the car @ 2000 RPM with a fan in front, temp coming out of the right outlet was 58* to 60*, depending on which thermometer you think is right.  Pressures were 40 on the low side and 280 on the high side.  According to the FSM (based on the FSM chart) the pressures should be 29 (+/- 2) on the low side and 245 (+/- 25) on the high side.

2nd test it was 86* and 68% RH.  Pressures were 41 to 42 on the low side and nearly 300 on the high side.  Outlet temp was 60 to 70 degrees.

My IR temp gun showed the inlet of the STV to be 89*, outlet was 105*.  Did it a minute or two later, it was 120* at the inlet and 160* at the outlet.

Clearly, I have a refrigeration problem, not a control system problem.  Looking at the FSM, my problem fits a bad STV and/or expansion valve.  Compressor is good because of the pressures.  When I first started the test, the low side was 25 and over the 10 minutes it creeped up to 40.  Seems to work only for a short time and that time span can be short or long (intermittent problem).

I kept the gauges attached for a few hours after and the high and low side balanced pretty closely (around 110 low and 125 high IIRC), I don't think there is air in the system.

I'm tiring of having to open the system and put in my stash of R12.  I'd like to get some input as to what I should do at this point.  New STVs are not available, guy on eBay sells used/tested ones for $120, I'm good getting what I need, I just want to be done with it.

Your thoughts?

I'll post pics of today's work in a bit.

[chrisntam]

Adding pics from today.

First pic is of the sight glass with the car off, 2nd pic is with the a/c on and engine @ 2000 rpm.  The "foam" is passing by the sight glass very quickly, not sure if they are "bubbles".  FSM references both bubbles & foam.  I always thought if the charge was ample, the sight glass would be perfectly clear, like the 1st pic.

Next pics are the set up, first gauge pic is the first test, the 2nd gauge pic is the 2nd test.  3rd gauge pic is after a few hours, pressures are equalizing.

Next pic is of the temp probes in the vent on the 1st test.  Last pic is showing the cool timing light (showing 2070 rpms) I have yet to figure out how to use....

[cadillacmike68]

The STV freezing up like that is usually an indication of moisture in the system, low refrigerant or a restriction, or any combination.

The system is working but there is something internally wrong with the refrigerant.

An Evac, flush and recharge would be in order.

["Cadillac Kid" Greg Surfas 15364]

Chris,
You do not mention anything about replacing the dryer/receiver.  Yes, using R-12 the site glass is supposed to be absolutely clear with the system running. I believe your system is designed to hold 3-1/2 pounds of R-12. If the cans are 12 ounces each then 4 cans is just 3 pounds.  The symptoms you describe would indicate either a shortage of refrigerant and/or refrigerant with some moisture in it.
In regards to the front seal leaking, one of the most common causes of seal destruction is not priming the seal before charging and starting up the compressor.  The compressor has to be turned over several times (I usually shoot for 25 or 30) to get the oil pump primed and get oil to the front seal before it is put under stress.  It is the oil that seals the system.
Also, just a note that if the oil level in the system is low and not enough is circulating, beside damaging the compressor, components like the POA ans the TX valve become "sluggish"
Also be sure the TX thermal bulb is clamped on the suction line tightly in the 3 o'clock position.
Greg Surfas

[chrisntam]

Yes, new driers were installed.

I think the failure to manually turn the compressor is why the front seal leaked.

The bulb is currently at the 12 o'clock position.

If it's low on Freon, why are the pressures high?

The system is exhibiting similar symptoms with first compressor/evac/charge as with the 2nd and 3rd compressor/evac/charge, though this is the first time I've put gauges on it and did a performance test.

I'm using old Freon from back in the day - 12 to 14 ounce cans.  Since they are under pressure, I doubt they are getting moisture in them.  Where's the moisture coming from?

Seems like the issue is intermittent, it will initially cool, then fade to warm.

[Big Fins]

When you evacuate the system, how long are you letting the vacuum pump work. Texas, like Florida has very high humidity. Running the vacuum pump for a couple of hours with cooling breaks isn't out of the norm if the system was opened for a while and parts changed.

I get a 40 degree vent temp with the R-134A conversion. That's the compressor, parallel flow condenser and the VIR replacement parts. So far, 4 years and holding very nicely.

[chrisntam]

I can't recall how long I sucked it down (it was several hours), but I understand longer is better.  I've done it once, two different shops have done it once each.  Different compressor, two different driers.  Same problem.   Issue could be moisture (not likely), bad valves (possible) or lack of oil (possible).  Too bad the a/c system doesn't have a dipstick.  Don't some old Ford compressors have dipsticks?

I'm leaning on taking it to a place that can handle R12 and first let them diagnose the problem.  I'll make sure they are equipped (if needed) to flush everything, install new hoses, replace the expansion valve and STV, pour in the correct oil in each component, suck it down and charge it up and see what happens.  I bought an STV from this guy:

https://www.ebay.com/itm/67-68-69-70-71-72-GTO-Olds-442-GS-Impala-Cadillac-Skylark-A-C-POA-Valve-A/201451622220?hash=item2ee773cf4c:g:sdsAAOxyHslQ80Zf

I'm the 35th buyer, he's got 100% feedback, so they must be ok...

For the total job, that'll be $1,000.00, please drive through.

Or, I can do it, but I don't have professional flushing tools and I'd hate to not tighten a fitting properly and have my gold plated R12 leak out...



And I have yet to pull the front springs to see how that got fubar'd.

[TJ Hopland]

I think it was the York compressors that looked like they belonged on an air compressor that had some sort of gearbox or crank case oil separate from the refrigerant side of things.   I don't remember if it was Ford or Chrysler or maybe both?

[Scot Minesinger]

Chris,

The oil generally does not get removed unless you liquid flush the system with refrigerant already evacuated.

You could have too much oil in the system?  To much oil impacts ac performance - states this in FSM.  If hoses are original I would replace them, they may be OK now, but it is a potential issue that you might as well cure now.  However, I have re-used original 1965 ac hoses with OK success.  The problem is not your hoses because you get intermittent results, hoses would just leak down and no ac.

One problem is crappy quality replacement parts.  If you replaced the expansion valve that could be an issue?  POA could be an issue.  Charging could be an issue.  Crappy quality drier could be an issue.  Are you sure the refrigerant is genuine r12?  replacement that are not r12, like "Freeze 12" are around which will be problematic.

I would not take it anywhere based on past issues (exhaust and suspension).  You will be super happy if you fix it yourself and it will be done right.

[savemy67]

Hello Chris,

Or, I can do it, but I don't have professional flushing tools and I'd hate to not tighten a fitting properly and have my gold plated R12 leak out...

Some refrigeration mechanics pressurize the system with nitrogen to check for leaks prior to the final fill with R12.  You can do this yourself, but you really need to be set up for this, and know what you are doing.  If you take the car to a shop, ask the shop if they check for leaks via a non-R12 pressurization test.

Respectfully submitted,

Christopher Winter

[cadillacmike68]

4 pounds of R-12 in a 1970 DeVille.

[chrisntam]

Scot - the oil issue can be addressed after the flush, adding oil to each component in the proper amounts.  I'd say its genuine R12, given what the cans look like, and that I got them from different sources over many years.  The common denominator (appears) is my system, not the Freon.  I agree 100% on the current crop of parts as being suspect.  Hell, I worry about the replacement front wheel bearings I put in a few years ago.  When I sold parts in the '80s, I never realized how I would miss those days.  I recall walking past stacks of wheel bearings, a/c parts, power steering pumps, master / wheel cylinders, brake shoes, ignition parts, spark plugs, wires, oil with zinc in it - Several different brands to choose from, all AMERICAN made.   

TJ - I'll keep looking for a dipstick, it's got to be there somewhere!   

Big Fins - good job on rubbing it in that your a/c blows @ 40!   

Chris - I'll add in the nitrogen charge question while screening potential clowns who masquerade as mechanics.      If they have big black shoes, a red nose, puffy loose fitting clothes and orange hair, I'll know I'm in a safe place.   

Any ideas as to why the pressures are high (if it's low on Freon)?

I think if I take the shotgun approach, I'm bound to have a (properly) working a/c system.  I can generally hang parts, but diagnosis is not one of my strong suits, especially since the FSM is a bit vague as to what the problem is.  I think that back in the day, they wouldn't have any problem flushing the system, replacing valves and recharging, given the fact that Freon was $0.99 per can.  I recall when it went to $1.69, I thought that was outrageous and didn't buy any.  Now I gladly pay $15 to $20 per can.     Endicott or Hershey?   

["Cadillac Kid" Greg Surfas 15364]

Chris
Pressures are high because the system  being short of refrigerant does not have the capacity or ability to remove the heat the evaporator is trying to add.
Greg Surfas

[cadillacmike68]

Scot - the oil issue can be addressed after the flush, adding oil to each component in the proper amounts.  I'd say its genuine R12, given what the cans look like, and that I got them from different sources over many years.  The common denominator (appears) is my system, not the Freon.  I agree 100% on the current crop of parts as being suspect.  Hell, I worry about the replacement front wheel bearings I put in a few years ago.  When I sold parts in the '80s, I never realized how I would miss those days.  I recall walking past stacks of wheel bearings, a/c parts, power steering pumps, master / wheel cylinders, brake shoes, ignition parts, spark plugs, wires, oil with zinc in it - Several different brands to choose from, all AMERICAN made.   

TJ - I'll keep looking for a dipstick, it's got to be there somewhere!   

Big Fins - good job on rubbing it in that your a/c blows @ 40!   

Chris - I'll add in the nitrogen charge question while screening potential clowns who masquerade as mechanics.      If they have big black shoes, a red nose, puffy loose fitting clothes and orange hair, I'll know I'm in a safe place.   

Any ideas as to why the pressures are high (if it's low on Freon)?

I think if I take the shotgun approach, I'm bound to have a (properly) working a/c system.  I can generally hang parts, but diagnosis is not one of my strong suits, especially since the FSM is a bit vague as to what the problem is.  I think that back in the day, they wouldn't have any problem flushing the system, replacing valves and recharging, given the fact that Freon was $0.99 per can.  I recall when it went to $1.69, I thought that was outrageous and didn't buy any.  Now I gladly pay $15 to $20 per can.     Endicott or Hershey?   

Ha Ha. I had a bad wheel bearing set trash my entire front right axle assembly back in 2005. axle meted in two.

[chrisntam]

Chris
Pressures are high because the system  being short of refrigerant does not have the capacity or ability to remove the heat the evaporator is trying to add.
Greg Surfas

Should I add a can and see how the pressures do?  Could the low charge be supported by the fact that the pressures start low (I recall seeing the low side at around 25 for the first few minutes) and creep up (to 40) over 5 to 15 minutes?

Are bubbles and foam (in the sight glass) considered the same thing? 

After doing some reading, (I know others know this, but I didn't) the bottom of the drier is the storage area for the liquid refrigerant, it siphons up from the bottom and then mixes going past the sight glass?  So the foam/bubbles I'm seeing is the lack of refrigerant being siphoned up?

And the engine temp was moderately high, say around 215ish, even though I had the air mover in front of the radiator/condenser.  I'm trying to get a higher velocity fan that will mimic air movement of 40 mph... the one I have only has one speed, but I don't think the velocity is ample.

["Cadillac Kid" Greg Surfas 15364]

Chris,
In order for the system to work correctly the system must be fully charged, meaning the site glass should be clear.  Fully charge the system and try driving the car at say 30-40 mph to get adequate air flow over the condenser and adequate compressor speed to give you the needed capacity. Then see what the outlet temperatures are with the system on both High and Low.
Greg Surfas

[Big Fins]

Big Fins - good job on rubbing it in that your a/c blows @ 40!   

I didn't say it to break your chops. 
If you must know, it cost me a Gee-wizz to get it like that. I told the well established shop (Since 1958) to make it like you owned it. And he told me the number before he even started. That number was already in my head as I know, any Caddy, that the A/C is not right in, you are looking at $1000. No if's and's, or buts about it.

I told him if you can make it R12, do it. If R134-A can do the job as well, do it.

Okay, so sue me. It's near 45F. 

[chrisntam]

Thanks for the info Greg.  I think what I'll do is take it back to the shop that did the last work on it and let them give their opinion.  If they put 4 cans (12 to 14 ounces) in it in the summer/fall of '18 and I put a can in in June of '19 and it is still low, there must be a leak.  They can check that and give their opinion on the state of my refrigeration system.

Fins, I look to find humor in all this way wound-too-tight world, that applies here as well!  Just funnin' with ya!   I'd be happy with 55*!

["Cadillac Kid" Greg Surfas 15364]

Chris,
In our neck of the woods EVERYTHING has to be working at maximum efficiency to get satisfactory cooling. 
Greg Surfas

[Big Fins]

Fins, I look to find humor in all this way wound-too-tight world, that applies here as well!  Just funnin' with ya!   I'd be happy with 55*!

Yeah, I should have known with you. I still tread lightly here.

Good luck on getting the freeze that you need. In our temps, there is no substitute for cold A/C. It works, or it doesn't.