A/C Vacuum pump

[RVTRKN]

JB is a good inexpensive American made brand, a small pump is all you need for a small auto AC system. BTW, the standard for pulling a vacuum on a small 3 ton home AC system, is 500 micron or below. A quality vacuum pump, like JB can run continuos for days if needed. When I perform repairs on my own system and I have time, I will run it for 24hrs. Getting to 15 Microns is not necessary, and 250 or below would be my goal, but my pump is rated at 10 CFM, however a 3 CFM pump would work and get below 250 microns.http://www.jbind.com/products/product-search-detail.aspx?SKU=DV-3E

 

[NIsaacs]

Go big or go home. Get the two stage. Why am I sticking my nose in you ask???

I bought a Robinair knock off just like what is pictured. It is NOT strong enough to hold a solid 30 in Of vacuum. 29 to 29.5 and then it struggles.

My T/K tech / guru maintains you need a solid 30 in or your just wasting time and electricity. The moisture remains in the system and performance suffers.
Not so critical out where Dave is but very important for us that live with summer humidity.

Okay, I don't know squat about AC systems so I "might be wrong".....but I do understand a little about vacuum. I have a vacuum gauge in my Ford Cummins from day one. It had the rotary pump similar to the older Dodges, they pump continually. The vacuum output is totally related to elevation and barometric pressure. If you try to get more vacuum then is "out" there it ain't gonna happen.

 

[RVTRKN]

Vacuum pumps running controls are a different animal, but it would be interesting to see what micron yours is capable of. 30”hg is the lowest a anolog gauge will show, micron is the metric measurement to see accurate vacuum below 30”hg.

 

[JR]

Another question on vacuum pumps. Looking at a similar kit in the link I posted at the start of this thread, only difference being the vac pump. The one I posted is 3 cfm single stage, the other kit I'm looking at is 1.5 cfm 2 stage...and is almost an extra $200 for an otherwise identical kit. Can someone please explain the difference, why a 2 stage with lower cfm rating is that much more. Just trying to educate myself before making a purchase.

Thanks!

 

[JR]

Found on another website for a much better price, about another $60 over the 3CFM single stage

 

[mwilson]

I can't remember, getting old but there is something that won't work...I will ask Brian Monday....

I forgot to ask him, he's in the middle of a unit install on one of those wretched little Promaster's....great wagons but not very friendly when it comes to add ons...

I'll stayed at a safe distance....will catch him in the morning....

 

[Tuesdak]

I see some of the new units claim multi refrigerent capability, but this older unit says R12 only

Thoughts?
https://ashtabula.craigslist.org/pts/d/white-industries-air/6623191852.html

Yuck! I would get a digital scale type unit. R12 hoses and seals don't work so well with R134a so every valve and connection on the machine can leak.

Suggesting starting with a known good unit you can watch work.

I went the expensive way by starting out cheap: I bought a used dual R12 and R134a Robin air recycler for $200. The oil dump valves had quit and flooded the recovery compressors on it. Vac pump recovered with a couple oil changes through it. $1500 in repairs later I have a good machine. Repair to the stuck auto oil dump valve including a new compressor and "filter" (that's really just a dryer cartage). Didn't bother with the R12 side. When the repair crew turned on the old compressor to test it they took a bath in oil as it shot it out everywhere.

Sure it wasn't the least expensive way to get a good recovery machine, but, I already paid for it with side jobs let alone working on my own junk.

 

[JR]

I think for the time being I'm going to just buy a unit similar to what I linked in my first post. Vac pump, manifold with gauges and hoses and digital scales. Then purchase a 30 lb tank of R134a. Reasoning for this - Both my vehicles that bit the dust are already discharged so recovery is out of the question and I need to get them fixed now. At a later date I may pick up a recovery ONLY machine to round off the tool set . If I had more time I might be able to come across a good deal on an all in one unit but there just isn't anything out there that's used within arms reach I'm comfortable with and buying new ($3k-4k+) is not an option for a DIY guy.

At this point I'm still hung up on vacuum pumps. 3 cfm single stage vs 1.5 cfm two stage....if anyone can explain the difference here in laymen's terms I'd be eternally grateful.

 

[mwilson]

Fighting me....

 

[mwilson]

Found this picture quite by accident.....trying to pull 30 in on the Yulkon last summer when I fixed the block offs for the rear unit. I can't remember if this was pre leak or post leak....

I don't think it is powerful enough....

 

[Dan_69GTX]

Sorry to get into this a little late. Hopefully this will be helpful....I recommend the 2 stage unit as well - such as the 1.5 CFM vs 3CFM unit - it will take longer, but do a better job! At the lower vacuum, you really need to measure in Microns (as previously stated). You are not just trying to remove air, you are trying to remove any MOISTURE too, which boils at a very low temp at a good vacuum.

Re older recycler units - beware of the snap-on/ MRC machines. They were decent machines, but they wear out. Snapon will not sell you a service manual on it, but they might service it for you. $$$. I had several and sold them because of that.

Using an older R-12 unit - depends on the oil the compressor (in the unit) uses. R-12 used mineral oil and R-134a uses a PAG /Ester oil (synthetic). Don't mix the 2.

A/C sealer - NEVER NEVER NEVER NEVER..... use it. I have a sealant detector and will NEVER work on a system that has sealer in it - it WILL ruin A/C equipment, and will ruin your A/C system in the long run.

Some info you might find interesting - or REALLY boring.....:
Water boiling vs vacuum chart:
https://www.quora.com/What-happens-to-boiling-point-of-water-in-vacuum

MICRON - A unit used to measure high vacuums. One micron equals 1/25,400 of one inch mercury.

MICRON GAUGE - Instrument for measuring vacuums very close to a perfect vacuum. Some models can measure to 0 microns. (Using the 29.999 inches of vacuum chart.)

STANDARD DEGREE OF VACUUM FOR A VACUUM PUMP - 500 microns or below and must maintain that degree of vacuum for the time corresponding to the size of the system. The old standard was 1,000 microns or below.

VACUUM PUMP MICRON RATING - Newer models can be rated to 20 microns when hooked directly to an electronic micron gauge and no other connections.

The absolute perfect vacuum is 29.921 inches of vacuum or 0 microns. In air condition and refrigeration,
water/moisture boils out under a vacuum at about 1500 microns. The standard is to pull 500 microns and isolate. If any moisture is left in the system, the reading will rise close to or above 1,500 microns. All the data for the 500 micron standard was compiled for medium/smaller systems. When you start to talk about commercial and industrial situations, the industry standard is different depending on the size of the system.

Here is the controversial part. The absolute perfect vacuum is 29.921 inches of vacuum or 0 microns, which is said to be unattainable on Earth. Many of the Pressure/Temperature charts that you review are based on 30 inches of vacuum. For instance, Robinair lists their last entry as 29.995 inches of vacuum. That may seem quite trivial, but the difference for temperature boiling point of water/moisture can be staggering. In the same chart 29.95 inches of vacuum
is 6 degrees Fahrenheit and 29.995 inches of vacuum is -35 degrees Fahrenheit. Other charts list 29.999 inches of vacuum as their last entry.

 

[Dan_69GTX]

A few more random thoughts:
Air in the system - even 5% will greatly reduce the efficiency of the system

A mixture of refrigerant - bad - always make sure your supply is pure.

I'm sure you don't want to spend the $$ on it, but Neutronics makes a refrigerant identifier that will also tell how much air is in the system.

For the new R1234yf refrigerant - any reclaimer/recycler has to have an identifier and it must show OK before the machine will even run. Besides the new stuff costing about $70 per pound. So a shop needs ALL NEW equipment to service these vehicles.

https://refrigerantid.com/products/automotive-refrigerant-identifiers/

 

[Dan_69GTX]

Now all that being said...you will probably be fine with the initial kit to do a few units. Most of the time it will work just fine.

Around here I've yet to find a shop (I no longer work for the public) that has an identifier, or a micron gauge, or really knows what either is.

 

[RVTRKN]

The new auto shop machines do it all, to include the proper charge in one unit. The exception is acidic refrigerant which must be recovered and disposed of with a separate recovery designed to be connected to the all in one unit. The major purpose of achieving 500 or below microns is the removal of moisture. Moisture in the system will cause a restriction at the refrigerant control as well turn the refrigerant acidic over time.

 

[JR]

Thanks for the advice Dan. I ended up buying a 2 stage 3cfm unit. Got the rear lines ordered for the Mercury so hopefully this weekend will be trying the new equipment out. Did some troubleshooting on the VW last week, the passenger side fan would only run on high speed and would not kick on at all with the A/C commanded so I got the replacement installed last night. Fired up the A/C, it started to briefly cool but almost right away went warm and started making an odd groan from within the dash. I flipped the settings from hot to cold and a bunch of foam came blasting out through the vents . CRAP! Thinking I've got some blend door issues because now I'm not even getting any real heat . I am NOT looking forward to this job. Always something!

 

[Dan_69GTX]

The new auto shop machines do it all, to include the proper charge in one unit. The exception is acidic refrigerant which must be recovered and disposed of with a separate recovery designed to be connected to the all in one unit. The major purpose of achieving 500 or below microns is the removal of moisture. Moisture in the system will cause a restriction at the refrigerant control as well turn the refrigerant acidic over time.

Yup, the new ones do it all.. But they are many $$$$$.

Regarding acidic refrigerant, in an automotive environment the only acidic refrigerant would be R-12. When with moisture the Chlorine will become HCL (another reason to remove moisture). With R-134A there is no chlorine to react with. However, PAG oil is very hygroscopic and will easily absorb water - which can eventually cause corrosion.

You have a good point on the moisture. It will turn to ice particles at the expansion valve or orifice (whatever system the car has) and plug it up. As the system warms the moisture melts and then the system works again for a little bit - a constant cycle (and PIA).

When opening an A/C system up, it is recommended to replace the receiver dryer/ accumulator since it has a desiccant in it to absorb moisture. If I have a system open to replace an o-ring I don't bother. If I'm replacing major components or the system will be left open, I do.

If you will have a system open try and find tight fitting caps to seal the hoses, etc.

 

[Dan_69GTX]

Thanks for the advice Dan. I ended up buying a 2 stage 3cfm unit. Got the rear lines ordered for the Mercury so hopefully this weekend will be trying the new equipment out. Did some troubleshooting on the VW last week, the passenger side fan would only run on high speed and would not kick on at all with the A/C commanded so I got the replacement installed last night. Fired up the A/C, it started to briefly cool but almost right away went warm and started making an odd groan from within the dash. I flipped the settings from hot to cold and a bunch of foam came blasting out through the vents . CRAP! Thinking I've got some blend door issues because now I'm not even getting any real heat . I am NOT looking forward to this job. Always something!

Excellent choice!

Yes, it is ALWAYS something.

Oh yea, you stated about getting a 30lb jug of R-134A - now you need a certification to buy a large jug - just like you have needed one for R12 for the past 25 or so years. The little cans can be bought by anyone, and there is always waste and leakage with those cans. But government knows best how to "protect" us. The jugs have also gone up in price. Last year I bought them for $68 ea if you bought 4 or more. Last I looked they were $200 ea.

 

[JR]

I bought a 30 lb bottle of Dupont R134 for $160. That with a disposable tank. Refillables were a good bit more, and the few local people I've talked to said it's all but impossible to get one refilled without a refrigerant license .

 

[Dan_69GTX]

I bought a 30 lb bottle of Dupont R134 for $160. That with a disposable tank. Refillables were a good bit more, and the few local people I've talked to said it's all but impossible to get one refilled without a refrigerant license .

Good job!

 

[RVTRKN]

Try “Sams Club”, that’s were I bought my 30lb jug for @ $70.00. However, I had to pay for the membership that cost me @ $110.00 total, if my memory serves me right. The odd part was, I didn’t have to show my refrigerant license at the register when I paid for it.

Dan, good explanation of moisture complications, I was just making my point as short as possible.