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AC too cold?


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huntindog
User

May 19, 2017, 3:52 PM

Post #1 of 19 (805 views)
  post locked   AC too cold?  

I just finished an AC job on a 73 Blazer. Since the stock condenser isn't available, I installed a parallel flow one. 16x27.
The AC airbox was rebuilt and everything is new, as far as the mechanicals go.

It only took a little less than 3 cans of R12, instead of 48oz like the book calls for. I attributed this to the smaller volume of the PF condenser.

Performance is good. Maybe too good. It will pull down to 32.5 degrees on the highway. city streets here in Phoenix today saw sub 40 degrees a lot. The compressor is not cycling off @ 32.5.
According to the specs on the switch I bought, it should be cycling of @ 28 psi, or about 30.1. As far as I can tell, it is not icing up.
It was a pretty nice day here in Phoenix. About 82 when I was driving it. I have read where these PF condensers can really increase the performance....and maybe when it gets hotter, the vent temps will be more in line with what I am used to seeing.
Everything appears in line. Evaporator inlet /outlet temps equal, the condenser is shedding heat really well. The outlet is close to ambiant temp, and the inlet too hot to comfortably keep my hand on it.

Thoughts?


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 19, 2017, 4:08 PM

Post #2 of 19 (801 views)
  post locked   Re: AC too cold?  

? Understand lower charge with new condenser and you are still using R-12. You really should never see a true 32.5F at a panel vent as it gained 3-5 degrees from evaporator to vent just heat in the ducts.
Seems nice but will if humid freeze up evaporator and understand not usually humid in Phoenix.


Help me - this is old and can forget. Is this a CCOT system with the cut out switch on the accumulator? If so and again I forget which direction you can adjust the cut out pressure with a flat head screwdriver with just taking off the switch. On threaded end should be a screw seen only with it off. Remove fast as there's a leaking time while unscrewing that type. Clockwise or C. Clockwise just a 1/4 turn in or out the low pressure cut out will change visibly by pressure or checked for continuity.


Warning! Adjusting that screw many will begin to leak a lot younger than this. New would likely be set for 134a a slightly higher pressure to cut out.


Be ready if you touch the thing so you don't lose your R-12. There was OE a Schrader behind the switch - no telling after all the years what's there now if OE for this or what as almost no chance these parts could be the first ones on this vehicle meaning mostly an accumulator so IDK what was fit in if replaced,


T



(This post was edited by Tom Greenleaf on May 19, 2017, 4:11 PM)


Hammer Time
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May 19, 2017, 4:47 PM

Post #3 of 19 (790 views)
  post locked   Re: AC too cold?  

You don't say how you concluded that this system was actually full with the reduced charge or what the high side pressures were running.

What are you using for a condenser fan?



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huntindog
User

May 19, 2017, 5:28 PM

Post #4 of 19 (785 views)
  post locked   Re: AC too cold?  


In Reply To
You don't say how you concluded that this system was actually full with the reduced charge or what the high side pressures were running.

What are you using for a condenser fan?

Went with a combination of feeling the inlet/outlet of the evaporator, acceptable vent temps (had 43 @idle) and pressures. I had about 34 low, and up to 220 high. Decided to quit then. When I let the system suck the liquid R12 out of my gauge hoses (10 footers), I really thought that may have put it into an overcharge... Then I get this kind of performance driving it.

I am beginning to think that the clutch cycling switch is faulty. It is new, and has a sticker on it that says R12.... But I bet it is set for 134... That would make the cutout 25 psi, and 23 degrees.
I had this problem before, and purposely got a different brand because of it. The last one was a Santech, and this new one is a 4 seasons.
Any other brands I should look to?

As for the fan, it is a stock engine mounted mechanical fan with a heavy duty thermostatic clutch. Almost new.
I do have some rubber that just arrived today to seal it better to force all incoming air to pass thru the condenser... Though with the performance I am seeing, it probably isn't needed. It does fit very well. Sitting in the drive at idle without the clutch engaged, it will duck s dollar bill right tight to the condenser.


Hammer Time
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May 19, 2017, 5:31 PM

Post #5 of 19 (779 views)
  post locked   Re: AC too cold?  

Where is your low pressure port in relation to the cycling switch?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



huntindog
User

May 19, 2017, 5:36 PM

Post #6 of 19 (774 views)
  post locked   Re: AC too cold?  


In Reply To
Where is your low pressure port in relation to the cycling switch?


They are both on the accumulator towards the top pretty much opposite one another


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 19, 2017, 5:39 PM

Post #7 of 19 (770 views)
  post locked   Re: AC too cold?  

OK, I just wanted to make sure it wasn't on the compressor and giving you a lower pressure than the switch was seeing.

It sounds like the switch is the issue, whether you adjust it or replace it.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



huntindog
User

May 19, 2017, 7:31 PM

Post #8 of 19 (763 views)
  post locked   Re: AC too cold?  


In Reply To
OK, I just wanted to make sure it wasn't on the compressor and giving you a lower pressure than the switch was seeing.

It sounds like the switch is the issue, whether you adjust it or replace it.

Are there any brands other than 4 seasons and Santech?
Having had the issue with both, I bet they are from the same production line.
I really don't want to adjust it, Heard too many stories about that causing leakage... And they instructions with the switch states that as well.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 19, 2017, 7:34 PM

Post #9 of 19 (759 views)
  post locked   Re: AC too cold?  

What about the shraeder valve. Is the switch actually contacting it?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



huntindog
User

May 20, 2017, 1:03 AM

Post #10 of 19 (744 views)
  post locked   Re: AC too cold?  


In Reply To
What about the shraeder valve. Is the switch actually contacting it?


Hmmm. Not sure. It is screwed all the way on. The accumulator is new. Perhaps the water on the condenser trick will tell the story.


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 20, 2017, 3:01 AM

Post #11 of 19 (741 views)
  post locked   Re: AC too cold?  

Don't touch the Schrader valve it might just leak. New switch so should tolerate adjustment. If you remove that lube the threads and "o" ring if you didn't or it will leak messing with it.


You need split second know accurate temps and pressures. I don't think your thermometer is correct. You aren't off that much and now need to know if you see frost or just a wet return line and cold accumulator. Rev engine up over 1,000 to 1,500 or so for tests.


You said 3 cans of R-12? 12oz cans or 14oz cans - they made both sizes. That if you got all of it in could be about right 14X3 = 42 some systems were between 44oz to 52oz with OE condenser so you are there or close. You could just be close on these not spot on. Last condenser changed to HE from OE tube and fin said to reduce charge by 10oz right on it just were doing that as nothing else available and said the difference.


Factors in everything. I'm in the Northeast - All weather can happen except not the super hot and super dry air both. Altitude matters and known humidity and dew points. They will be listed here just put in your zip code and find the closest reporting station - no joke. Link to the site is...........
> http://www.intellicast.com/...px?location=USAZ0166


Dew points are in the 20s and elevations for Phoenix range around 1,000 to 1,500 matters. I'll plead not sure how it would make it colder without a problem measuring temps. Pressures probably close enough to any charts. Infrared touchless thermos may be best on solid items.


This may not work. Today right now reporting stations..................WH0262 Test StationPhoenix, AZ
33.45°N, 112.08°W at 1280ft 61.5°0.0mph at 186°S
Updated 13s ago
More Details Central CityPhoenix, AZ
33.45°N, 112.08°W at 1190ft 73.4°0.0mph
Updated 3m 22s ago
More Details Deer ValleyPhoenix, AZ
33.45°N, 112.07°W at 1478ft 68.2°
2.0mph at 40°NE
Updated 8s ago
More Details






Good luck. Take all info you get and do verify it with other equipment especially thermos as I really think that's screwing you up and wrong just off a few degrees. If you can find one try a wired digital remote put end down a center panel vent,


T



huntindog
User

May 20, 2017, 3:22 AM

Post #12 of 19 (735 views)
  post locked   Re: AC too cold?  

It is dry here. So no frost or sweating.
I actually went and bought a new digital thermometer yesterdaym as I didn't believe the two I was using. It is within a helf a degree of the others... The digital ones are the fast acting ones.

I do have a switch with an indicator light on the dash that I can use to cut the power to the compressor, and when the light is on, the compressor is running... I did this years ago when I used to tow with it. I could cut the power for hill climbing and still get a little cool air .
So I am sure that the compressor has never cut out.

If that cycling switch is working right, it has to cut out at those low temps.... Right?

Hammer may have something with it not engaging the schrader valve... Will check on that. I could always move it to the other port to see if that one works.


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 20, 2017, 4:21 AM

Post #13 of 19 (727 views)
  post locked   Re: AC too cold?  

OK - trust your double check of thermometers. BTW I'm at 232 ft. Elevation right now 52F w RH @ 82% - don't ask I'm a total heat transfer nut case monitor all, all the time. This is W. of Boston (is at sea level) by ~ 25 miles elevation begins to rise.


I never worked on anything at elevation yet lived in Denver for a year at a mile high +/- - super dry air can't sweat so understand. It matters - tire pressure changes - a lot of bull changes - boiling points, air density by elev. and temp both.
Another thought: Your accumulator may be generic fit for a few vehicles? You may be able to change which port you use for service port and for switch? I do think turning screw CC (counter clockwise) raises the cut out pressure but don't touch it yet. Cold is fine except for icing you may never get where you are. Your working A/C probably never makes puddles of water under vehicle when shut down either.
With that it's more efficient but less BTU because of altitude not by much.


Do know R-12 and type of vehicle will be tolerant of being off because it's a CCOT system just catches the extra, felt by accumulator being cold to touch - that's a good sign it's just slightly more than required to work.


Problem isn't so much icing as you could just shut it down for 1 minute it would melt and work again the problem would be if it could return liquid R-12 to compressor would lock it up. If hoses returning have tight insulation or accumulator IMO not needed and take it off return lines. Causes rust/corrosion over some years.


You are very close to perfect IMO. Just would hate to see you mess up and make a leak adjusting dang switch if really needed to do so at all. It probably wouldn't stay that cold for long enough?


Trivia side note: Schrader is a name of inventor "August Schrader" but spelled different ways and auto corrected by my device! Named for the idea but there are different types that fit and sizes totally. I've never been able to loosen one to touch better without making a leak you don't want. Problem would be with the switch not screwing down tight (hand tight plus a little about) just off. Another may or may not be better by a couple PSI if you wish or worse - can't know quality of stuff stinks.


Your call if you see super low temps to always use high blower fan should help with less air "residence" time at evap same BTU still comes thru.


Other if you have a floppy ended elbow of drain rubber tube is to cut off the floppy tip of it! Some extra cool will blow out of it then.


Tom



huntindog
User

May 20, 2017, 5:55 PM

Post #14 of 19 (706 views)
  post locked   Re: AC too cold?  

Did some more today. Installed the rubber sheeting I ordered around the condenser. It turned out really well.

I unscrewed the misbehaving switch from the accumulator. It made a pfft noise, and a click... and the inside of the switch had oil in it.
When I screwed it back on, it clicked... That tells me, that it is working, and it is engaging the schrader valve.

So it may say R12 on the sticker, but it is performing like a 134 switch.

I have done some searching, and I see that there are many such switches for other makes available. I would be up for installing one of them, and the matching wiring, to get this working right.

I have zero experience with the other brands as far as AC goes soooo..

Any reccomendations?


(This post was edited by huntindog on May 20, 2017, 9:17 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 21, 2017, 1:53 AM

Post #15 of 19 (694 views)
  post locked   Re: AC too cold?  

? Can't find the chart this second but R-12 should actually cut out at a lower pressure than 134a but parts are just parts and plenty aren't right on.


It works - just a bit low. Most wouldn't notice if by the time it could freeze it would click off and would melt that in no time. For conversions never touched them and worked fine so R-12 doesn't mean too much on that switch unless rubber seal wasn't up to speck - not anymore though. That's the only problem. If humid enough and did that it would/could make an iceberg and air flow go slow then when say you just parked it make a huge puddle and work yet again later like there was no problem.


Because it's new I think I just swap it out for another


BTW: You can use a switch for many Ford products fits just wires and plug you would have to adapt. They are larger and all did adjust as said and many leak. I keep a coffee can full of them because they usually remove by hand easily and a junkyard let me have them plug and all with wire to splice,


T



huntindog
User

May 22, 2017, 11:20 AM

Post #16 of 19 (659 views)
  post locked   Re: AC too cold?  

Just drove it home from work. 96 degrees, and a much hotter interior. Within 2 miles @ 40 mph the center vent temp was 41 degrees. It continued to drop, stabilizing @ 40.1.

The compressor never shut off, though it probably would not on this short hot trip.

Going to call 4 seasons today to discuss the misbehaving switch..
I do have the chart. It shows that an R12 system will freeze at a higher pressure than 134... IIRC with this switch cutting out @ 25 psi, that would be 25 degrees.


Hammer Time
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May 22, 2017, 11:25 AM

Post #17 of 19 (655 views)
  post locked   Re: AC too cold?  

I really wouldn't be too concerned with it. Some of the Chryslers cut out at 18PSI and don't freeze. Even it it starts to freeze, it will cut out soon and warm up.

Unless you actually experience a solid freeze up I would just drive it. Keep the blower speeds off the lowest speed.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



huntindog
User

May 24, 2017, 3:37 PM

Post #18 of 19 (620 views)
  post locked   Re: AC too cold?  

4seasons said to play with the adjustment on the switch... Carefully since it is touchy.
He also said it may be low on freon.

Today I hooked up my gauges, and fed the lines thru the vent window to the passenger seat. I have 10ft lines, so it reached easily. I then had my wife drive while I monitored pressures and vent temps.

It was about 102 out when we did this. City street driving the numbers were all over, but nothing looked out of ordinary.
Then we got on the highway for probably 10-12 miles.

High pressure ran 220, and low 27.. vent temp hit 44.

We returned home. I disconnected the gauges letting the system suck the liquid out of the high side line.

I then repeated the drive. vent temp hit 43.

I think when my gauges were hooked up, that I should have had a little higher low pressure... But draining the high side lines when disconnecting should have put a little into the system.
That could put it spot on..

I am considering doing this again tomorrow. But having a can of freon hooked up, and adding a little to the system as we go down the highway. I would have another thermometer measuring outside air temps, and add freon till the high side hit exactly 2.2 times the outside temps. Then disconnecting the gauges without emptying the high side line.

Thoughts?

P. S. I am not messing with the switch for now


(This post was edited by huntindog on May 24, 2017, 3:43 PM)


Hammer Time
Ultimate Carjunky / Moderator
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May 24, 2017, 3:47 PM

Post #19 of 19 (614 views)
  post locked   Re: AC too cold?  

Man, you just have too much time on your hands. Anybody else would be jumping for joy with these numbers.

Just leave it alone and drive it. I don't see anything wrong.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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