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Coral Red Syd's Avatar
 
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AC High and Low Side Pressure Gauge Fitting and Vaccum

The easy questions are the hardest. Did a search and nothing so here it is:

Question 1:
- Testing the AC high side and low side on the compressor.
- Have an air compressor gauge (up to 300 psi).
- Where can I find a fitting that fits the Schrader valves?

Question 2:
- Need a recommendation on a good vacuum pump to evacuate the system. By 'good' I mean one that will last many years for several p-cars and can handle my existing R12 system or R134 if I later convert.

Question 3:
- Would you recommend a leak tester or the soapy water test.

Thanks in advance.
CrS
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Old 09-22-2006, 07:22 PM
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You need a set of a/c manifold gauges. There are sets for R12 and 134a.

You need to be able to open the system to the gauge and close the system.

If you don't have the right equipment, don't even try reading the pressure.

You can pick up a set of 134a gauge at Harbor Freight or Ebay. Use set of r12 gauge can be found on eBay.

Best tester for finding leaks is the electronic sniffer.
Old 09-22-2006, 07:47 PM
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Thanks, your comments get me on track now.
Wayne's 101 projects book says an "air conditioning pressure gauge" p125 and got me thinking of a compression gauge as used to measure cylinder pressure...

Can you recommend a good vacuum pump?

Thanks
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Old 09-22-2006, 08:20 PM
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Quote:
Originally posted by Coral Red Syd
Thanks, your comments get me on track now.
Wayne's 101 projects book says an "air conditioning pressure gauge" p125 and got me thinking of a compression gauge as used to measure cylinder pressure...

Can you recommend a good vacuum pump?

Thanks
Two completely different type of gauges.

Robinaire makes a nice vacuum pump.
Old 09-22-2006, 09:44 PM
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You probably need all this stuff

ac starter kit

Search around for the best price

The forum associated with the above is prettty good also

ac forum

I have no association with the above
Old 09-22-2006, 10:03 PM
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Good vacuum pump (buy extra oil too):

http://www.thetoolwarehouse.net/shop/ROB-15434.html

Good harness:

http://www.thetoolwarehouse.net/shop/MAS-84772.html

I believe shipping is free is you buy more than $200; pump is heavy.

Also get safety goggles, refrigerant can dispensing valve and a couple of bimetallic dial thermometers.

Last edited by Jim Sims; 09-23-2006 at 07:25 AM..
Old 09-23-2006, 07:18 AM
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There are lots of good threads here, just look under
Jim Sims name in a search.

And there is this as well:
http://www.griffiths.com/achelp/achelp1.html
Old 09-23-2006, 12:57 PM
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Thank for these. Valuable learning here.

Two last questions (I hope). I'm going to use freon cans and was wondering how good the side mount can tap as shown in the starter kit (above) was.

Also will the dye hurt the Porsche AC system?
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Old 09-26-2006, 07:58 PM
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If you use dye, and the evaporator coil is leaking, you won't be able to see the dye, but if you use an electronic sniffer, you can test the air coming out of the vent to see if there is freon mix with the air.
Old 09-26-2006, 08:59 PM
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Quote:
Originally posted by Coral Red Syd
Thank for these. Valuable learning here.

Two last questions (I hope). I'm going to use freon cans and was wondering how good the side mount can tap as shown in the starter kit (above) was.

Also will the dye hurt the Porsche AC system?
Having the dye added to the system is pretty much SOP today, because:
Say for example you are testing for leaks with an electronic sniffer at a connection(s) or component(s) on the high side, and the system pressure is (for example) 225 psi and the sniffer does not detect a leak. Then a few days later it is much hotter outside (ambient) and the high side pressure jumps near 300, chances are any small or potential leak point will be more likely to push out refrigerant (and the dye). Dye does not always show up at leak small points, but for the cost and simple procedure it is well worth the effort. Avoid any refrigerant additives such as "leak sealer" or "revitalizers" .

With respect to charging with small cans:
a) Know the capacity of the can, 12 oz or 16 oz.
b) purge the air from cans hose before connecting to the system
c) Wear safety glasses and don't expose R12 to open flames or heat ranges of the same.
d) Remember that most of the retail "starter" kits are rather inexpensive, so you get what you pay for. Insure the seal is attached to the tap port that contacts the can, and make sure the device that punctures the can is retracted before you attach the can. If you don't have a formal refrigerant service gauge set then find a friend that has one and who has done the procedure before (hopefully more than one time) to guide you.

We can go on to mention other things you are suppose to know before you start the procedures, however most of them have been covered already in other posts......
soooooooooooo READ before you start.
Old 09-27-2006, 04:36 AM
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An addition to the original post... the quest continues
Done the reading and getting there
1984 Targa has the original R12 system.
Ready to pull a vacuum and recharge the system with R12 from small cans, check for leaks, and chase down problemactic areas with a sniffer.
Question: I see from the Bentley manual that total system capacity of AC oil is 2 oz at the compressor, what type of oil should I put with the R12 system and how should I add the oil to the system?
Note: AC compressor is the original Nippodenso.
Also how much oil should I put in at this initial recharge?
One more, what will the system pressure be once I add the small cans of R12 to system capacity of 47 ounces?
Thanks all,
Cheers
CrS
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Old 05-04-2007, 07:36 PM
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Don't forget to get a shop blower or fan to blow air across the deck lid condensor. Without this extra step.... damage to your system could result.
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Old 05-04-2007, 08:30 PM
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+ 1 on the shop fan on the condensor (while the engine lid is open).

Damage to your system you must avoid.

(sorry, was trying to sound like Yoda there)
Old 05-04-2007, 08:48 PM
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If you've drained the compressor, replaced the R/D and flushed the condensers you will surely need to add more than 2 oz of refrigerant mineral oil (for R-12.) You will need a good vacuum pump; the compressed air powered venturi type are inadequate. The proper pressure when charged depends on the ambient air temperature. You need an R-12 table and thermometers. Be sure you connect the charging hose to the low side (suction side.) If you don't know what this means and how to do it, get some experienced help. A/C systems can blind, maim or kill you. Always wear eye protection.
Old 05-05-2007, 08:10 AM
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Thumbs down

Blowing air across condensers when charging or testing the system.......? I think you want to think about that idea.

Imagine you are driving your car and come to a traffic stop light, sign or simply traffic. Its a hot day, ac is on. If you sit there for long pretty soon "things" are going to start to heat up. The ac refrigerant pressures are going to rise. There are no shop or portable fans blowing across your deck lid condenser nor past your front condenser.

Thinking back on how you charged your system at home or back at the shop, aiming fans across the deck lid or the front of the car and checking or adjusting your refrigerant charge in that scenario, ..... is not going to help you when you are stuck in traffic without those fans. It will simply give you, unknowingly, false results.

Here is how it plays out, example:
When you charged and tested the system back home or at the shop, using "fans", the ambient was say 90F (hotter is always better) you had a high side pressure of 270 psi at idle (using giant fans blowing across the deck lid and pushing under the front of the car).
The following weekend you take the car out for a spin, its around 90F again, and you come to a traffic light and stop for awhile to watch the parade. What do you think the high side pressure will be "without" those fans from back home?

The preferred method of checking and charging the system is NOT to use "something" you won't have in the real world (such as the fan idea; the idea of placing small 12vdc fans on the deck lid is another topic) when you are out driving.

Aiming fans at the car, say at the oil cooler, when you are doing other things such as a tune up or dyno tests, does come in handy.

Its best to finalize or tweak the "safe" charge level of the refrigerant (using a P&T method) is to design it around a worst case scenario, which is sitting in traffic without shop or home "fans"; engine deck lid down.
Old 05-05-2007, 08:50 AM
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Kuehl,

This is an honest question, I'm not trying to be a smart Alec here.

If you're at a stop light or in my case a drive through fast food window, with engine on, don't you get some air flowing across your condensor due to the engine fan sucking air into the engine compartment? And the front one has a small electric fan, weak as it is, pushing some air through it as well? And 270 psi on my 134a system is like nothing. I've had to charge my system on a 100 degree day. At around 2000 rpm or so I'd swear I saw 340-360 psi, but I could be wrong. Am I about to blow an AC hose or seize the compressor with pressure like that?
Old 05-05-2007, 09:24 PM
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Rusnak,

No I don't think you are being a wisecracker. You are actually raising an important issue. The short answer to your question is "yes" your pressures are way too high.

The long answer as to why requires some pondering as there could be one or more reasons for excessive high side system pressures. Besides high pressures placing stress on your compressor, high temperatures also reduce the life of the compressor. Do you have a pressure cut out switch installed in the system? Have you considered adding additional condenser(s) capacity such as the Kuehl systems or others?


Stepping back, some off the cuff question I would ask:
1) How long did you pull a vacuum for?
2) How much refrigerant did you put in the system?
3) What was the ambient temp and high side pressure, at idle, when you finalized the charge?
Old 05-06-2007, 04:50 AM
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I have the venturi type of pump (I am planning to buy the electric one from Toolsource.com thanks to advice on this board) and pulled a vacuum for maybe 45 mins.

The amount of refrigerent I'm not sure of since it was about a year ago after I bought the new tail and condensor assembly. Basically I added about a can and a half, ran it and then added more. I usually have 3 cans of straight 134a on hand when I service the system for leaks or evac/ recharge. I found that when I added more it got really really cold. I hypothesized that it took more refrigerent to get droplets of liquid at the expansion valve to be released into the evaporator. I've never had the evaporator freeze up on me. Ambient temp was easily over 90F maybe closer to 100F, I don't recall. At idle I would guess around 290psi. The pressure climbs so fast with rpms.
Old 05-06-2007, 05:33 PM
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Just a suggestion.

Buy good equipment (gauges, pump, sniffers etc) no matter what it costs.

Evacuate at an ambient of 75F or warmer and for 3 hours.

Try to charge at an ambient of 80F or warmer, and adjust the charge amount based on pressures and temperatures.

Keep more accurate records of the procedure and results, such as ambient temps, pressures and refrigerant amounts down to the ounce.
Old 05-07-2007, 02:37 AM
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Kuehl,

thank you for the advice. 3 hours though? Won't my residential hobbyist type of pump overheat? What if it turns off to protect itself, do I try to shut the valves and then re-start the evacuation?

This is what I was thinking about buying:
http://www.toolsource.com/ost/product.asp?sourceid=&dept%5Fid=500&pf%5Fid=59320&mscssid=8F36QS6G42EX9JSP0GWUUSWAMCUJ9DC7

Also, I thought I'd clarify for those running R-12 that the pressures for 134a are significantly higher, which is why most people upgrade their pump to an ND, Seiko, or other rotary pump when they switch to 134a.
Old 05-07-2007, 03:23 PM
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