strange cooling

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grumpy old man
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Re: strange cooling

Postby grumpy old man » Fri Jul 27, 2018 9:29 am

So when I get home I will put the gauges back on the windshield and drive it to see what is happening. Should I bleed off enough refrigerant to get it to cycle the clutch, if it is overcharged as I recall that can affect the nozzle temp. Not knowing what the capacity of this condenser might it help to go to the Cad condenser, would it be worth a try? At this point I will do almost anything. I was running a garage for LAPD in the 90's and the crown vics had no problem maintaining nozzle temp at idle but they did have a pretty substantial electric fan between the radiator and the engine fan. It was common practice for a police car to be sitting at idle while the officer was doing whatever and they would maintain internal temp for extended periods of time. So I am thinking that there is not enough transfer of heat at the condenser, could be condenser capacity or could be air flow even though the engine temp problem seems to be cured.

At this point I do not know what this thing will do at more reasonable ambient temperatures as my only experience was Tuesday in the high 90's so larger electric fan, better condenser or bite the bullet and live with it?
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bohica2xo
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Re: strange cooling

Postby bohica2xo » Fri Jul 27, 2018 10:44 am

A driving test may have some answers. Increased airflow results will tell you if it is a condensing problem.

Not cycling under high heat load is normal. If you can reduce the cabin fan speed to minimum it should cycle when you raise the engine RPM above 1500 - 2000 RPM

Discharge air temp vs volume is always a two edged sword. Double the CFM but 10f warmer? which brings the CABIN temp in to a comfortable range quicker?

Yes taxis & cop cars idle all day, but once cooled down some it takes less to keep them cool.

It was 117f on the car thermometer in the wife's 2018 Equinox yesterday afternoon when I started it. It had been sitting in the sun all day, and it was 2pm. The ACC made the decision to run fresh air & 100% fan for the first 2 minutes, then switched to recirculate. It began to reduce fan speed just as the cabin started to be tolerable - probably 80f The wife put her hand in front of the now very cold discharge air and said "Finally! the A/C in this thing takes forever"
When in reality it had dealt with the 140f+ interior temp quickly & effectively with a programmed strategy.
grumpy old man
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Re: strange cooling

Postby grumpy old man » Mon Aug 06, 2018 8:30 am

OK so I spent most of Friday afternoon and some of Saturday morning putzing with the A/C. I decided rather than modifying the radiator header AGAIN I would go back to my original idea and stack the condensers. I got another condenser to match the one already in there,. the screw holes in the top and bottom strips match up so I just screwed them together and connected the hoses. The initial result was that the high side pressures came way down. That required more refrigerant, 48 oz, to get the high side pressures up enough (225psi) to get the accumulator to sweat. Ambient temperature in the garage was high 80's, according to the thermometer sitting on the shelf above the work bench, nozzle temp at 40 with the engine slightly above idle, climbing slightly at idle.

Sunday I drove it, the temperatures were in the mid 90's. Initially it was OK but when I parked it in the sun and came back a few hours later the internal temp was reading 140 on the thermometer that is presently living in the center vent. I was only a couple of blocks away from the freeway on ramp and 4 miles on the freeway the nozzle temp never got below 60. When I dropped off the freeway to the surface streets the nozzle temp came down into the 40's within a couple of blocks.

I have been chewing on this since Sunday afternoon and here is the theory I have extrapolated. What is the possibility that the orifice I have in there is too restrictive? It would explain the high side pressures I had before changing the condenser arrangement. The airflow on the freeway with the cooling capacity of two condensers would not let the high side pressures get up enough to push the refrigerant past the orifice. On the surface streets the lesser airflow brought up the high side pressures and pushed more refrigerant through. The orifice that is in there came across the Ford parts counter and supposedly is for a '98 Crown Vic police cruiser. One of the first lessons my dad taught me was that just because a part is new does not mean it is good. So the questions are is it the wrong one, is it defective or is it just not the right one for the strange collection of parts I have in this system?

I once ran across a chart showing the color code and size of the orifices but can not seem to find it again. Do you know if the orange orifice is actually correct for the '98 Ford an if it is what is the next size up?
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bohica2xo
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Re: strange cooling

Postby bohica2xo » Mon Aug 06, 2018 10:34 am

You would appear to have the OEM tube, but with china churning out parts who really knows.

Here is an old post covering the sizes:
https://www.autoacforum.com/messageview.cfm?catid=20&threadid=10818

I would avoid any "self adjusting" tubes, we have never seen any gains from them.

I have never had anything good to say about the CCOT system in general It is one big compromise, to replace a 15 dollar valve with a 20 cent part. This is why some people have success using non-standard tubes to meet the needs of a local climate. You could try a white .072 tube for more flow.

I have converted a few CCOT systems to CC-TXV. That way you get an actual variable orifice with a feedback loop. It is good in areas where the heat load means that at idle there is not enough compressor volume or condenser capacity to deliver clean liquid to the expansion device. Sloppy, turbulent foam does not meter well through an orifice. The TXV will open all the way, which reduces high side pressure during long hot idle conditions. It still cycles to control freezing.
grumpy old man
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Re: strange cooling

Postby grumpy old man » Thu Aug 09, 2018 6:03 pm

I put in the .072 tube and there is little change. The problem with this Pontiac is that I need 40 degree nozzle air at full blower just to maintain a livable cabin temperature in 100+ degree air. Nothing is insulated, a dark blue convertible top and untreated glass. Driving on a sunny day you can feel the heat load and if you happen to get stopped under an overpass out of the sunlight you can feel the cabin cooling off in the time it takes for a light to change!

What does it take to install a real expansion valve? What valve would I use and how to connect it to the evaporator. The condenser to evaporator is just having a different hose made. Or............ somewhere in this exchange you alluded to the Ford units not being that great to begin with. Is there something else that I can use for a starting point in a similar housing with a greater cooling capacity. I just need something in a similar housing that I can position on a flat firewall over the existing hole, or a different evaporator that I can adapt to my housing. Something in a similar firewall mounted housing I could whack off the fan housing and marry it to the custom one I made for this installation. The inside unit does a good job of directing the air flow and it is already connected to the Pontiac heater control. I adapted the Ford vacuum valve and fan switch and the temp door is now controlled by the Pontiac cable. It all works fine I just need to get this cooling corrected, and if the car was not so hard to cool and maintain we probably would not be having this conversation.

What does a Cadillac evaporator look like? If I use a Cad condenser and evaporator it would be a matching unit assuming that the compressor I am using will drive it. I am reaching a point of desperation.
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bohica2xo
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Re: strange cooling

Postby bohica2xo » Thu Aug 09, 2018 11:30 pm

Well, a couple of things come to mind. Compressor Speed & Compressor displacement.

Your fan speed was way down, and you have corrected some of that.

But I can't seem to find any info on your compressor in this thread. Ice touched on this in his earlier post, where he describes using a 138cc/rev compressor with a 1.39:1 Overdrive from the crank. That is an 8 cubic inch compressor.

GM's standard compressor for factory A/C in the 1960's & 70's was the A6 with a displacement of 12 cubic inches per revolution.

The Crown Victoria your evaporator came from had an FX10 compressor, those are 10.4 cubic inches.

So you see the speed vs displacement issue. You can replace a 10 cid pump with an 8 cid unit - but it needs to turn faster to make the same volume. At road speed both units will make enough volume, but at idle the difference is very noticeable. Road test your car. Run it in low gear at 3500 engine rpm & see what happens to the vent temperatures.

Doing the swap to a TXV on a CCOT system is pretty straightforward. You keep all of the existing system except the orifice. The accumulator stays, as well as the cycling switch. You add a receiver / dryer in the line from the condenser to the expansion device. Select an expansion valve that has internal equalization and make up s very short hose to fit between the TXV & the springlock on the evaporator inlet.

The only issue I see in your case is the sensing bulb attachment. I generally do this conversion on ford trucks, and they have a fair bit of tube available at the accumulator. The Crown Victoria as I recall has very little between the accumulator & the firewall. You really need to keep the sending bulb close to the evaporator outlet. I suppose you could clamp it to the side of the accumulator & insulate the whole thing, or make a short tube adapter to fit between the evaporator & accumulator.

I would road test a little more to explore the compressor volume issue before replumbing for a TXV. The 1998 Crown Vic cooled well enough to keep the black town car guys happy here. i suspect that evaporator has enough capacity for your needs.


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grumpy old man
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Re: strange cooling

Postby grumpy old man » Mon Aug 13, 2018 8:58 am

I went back and read the entire thread, sort of like job notes. I realized that I had the original weird problem where the auxiliary fan was being wind driven and generating enough current to keep the clutch engaged That got me chasing all the strange rabbit trails ultimately reaching the point where I was just throwing stuff against the wall to see what might stick.

So I checked with oid air products and found that i probably have the same compressor that ice used on his system. 138cc (8.4") and the same overdrive. The crank pulley is 7.25" and the compressor is 5.25" which if I remember my high school algebra at all comes out to 1.39 to 1. I did drive it around a bit yesterday, temp was mid 80's in the garage so in the sunlight probably 90 +-. Driving 35 mph in 2nd gear nozzle holds steady at 40 and the clutch not cycling (I can tell by the ammeter). Shifting into 3rd nozzle comes up to 42. Stopping, the nozzle takes 15-20 seconds to climb up to 60 where it holds steady. This is with the .072 tube.

I am going back to the beginning and take this thing step by step. Some time today I will put the original tube back in, put the gauges back on the windshield and drive it for a couple of days to generate some accurate data. If I can get this thing operating acceptably for the time being chances are sometime this winter it will be going through an engine change. I have been playing around with the engine since I got it running and have gone through several induction systems, different carbs, working right now on the 2nd injection system and can not get this thing above 13 mpg on 4 buck gas. I am vacillating between an LS and a Hemi. In either case if I use the compressor that comes with the engine it should solve the compressor at idle issue.

When I get some data I will be back.

While I was on the old air website I saw an expansion valve. it has a tight wound sensing coil on the end of the tube and it appears that if I mount it up near the evaporator outlet I can split the clam shell and put it inside catching the air coming through right at the outlet. So depending on what I find that will probably be my next thing.
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bohica2xo
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Re: strange cooling

Postby bohica2xo » Mon Aug 13, 2018 9:52 am

Which EFI are you running? 13mpg sounds way off, unless you have a huge cam in it... i had a 455 that got 12mpg with a Quadrajet.

Your 2nd gear / 3rd gear test shows the volume issue. Even with road speed & ram air, you still can't produce enough volume.

You could swap out to a V7 compressor & leave the Orifice tube in it.
71403
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Re: strange cooling

Postby 71403 » Mon Aug 13, 2018 4:01 pm

grumpy old man wrote:working right now on the 2nd injection system and can not get this thing above 13 mpg on 4 buck gas. I am vacillating between an LS and a Hemi. In either case if I use the compressor that comes with the engine it should solve the compressor at idle issue.


Injection as in EFI? Fuel-wise the only thing EFI has over a well tuned QJet is decel fuel cutoff. Hemi is a money pit with extremely limited aftermarket support, leave that to the Mopar purists. LS is the modern day small block chevy, huge base of support and best cost to benefit ratio of any powertrain choice.

To keep this forum-relevant my DD is a LS swap with a V5 compressor. :D Next DD is going to be the newer direct injected LT motor with the electronic variable displacement compressor.
grumpy old man
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Re: strange cooling

Postby grumpy old man » Mon Aug 13, 2018 11:43 pm

Engine is a 389 with a very short camshaft. Problem is that there are no aftermarket parts for pre '65 Pontiacs. If I could find a 4 barrel intake and use an a of b series AFB I might be able to squeeze a couple more mpg out of it but it needs premium fuel because of the compression ratio.

The original Rochester 2bbl was good for 11-12. I had a modified GM tbi that was good for another 1 or 2 on a really good day but we could never get the thing to get along with the roto-hydramatic, long story. I presently have a Holley sniper 2bbl tbi that runs great but doesn't give any more mileage. This is probably my last car because I don't have another build in me so before I finish I need to get the thing right so down the road there are no regrets.

Pardon my ignorance but what is a v7 compressor?

I believe that I saw on the Sanden website a variable compressor but I do not know if it would fit my brackets.

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