Ninja tips: AC systems Options

[technicalninja]

This thread is my base AC thread for suggestions, questions, whatever...

I run
https://granburyautoac.com/

I specialize in automotive heat and air conditioning systems.

I've been doing AC work since 1983 and have seen all of the changes, good and bad, that have occurred over the last 40 years.

I'm keeping the first post short as they always show up at the top of each page and if long, they clutter up the thread...

[technicalninja]

1st tip and this might be the single most important...

DO NOT purchase any R134a that has anything in it!!

You want the cheap stuff! No AC pro, no easy fill cans, look to the low side of the refrigerant display to find the R134a that is just R134a.

It is perfectly fine to buy this at Walmart. R134a is a chemical and doesn't need fancy labels.

Most of what available at the parts houses has both oil and sealant in it...

The oil doesn't bother me that badly, but the sealant does.

I've never seen it fix a leak, but I've seen too much of it TRASH entire systems.

All of my recycling machines state in the very first sentence of the warranty section

"Any sealants found in the machine void all warranties".

The sealant crap can be the death of your system. Avoid at all costs!!!!

The straight R134a is also the cheapest alternative. Be a cheapskate regarding your refrigerant...

[technicalninja]

2nd stupid important tip.

Change the service valves every single time you evac and charge a system.

The little valves will seal perfectly for 10+ years the very first time they are used.

If they are only 6 months old they might seal a second time. If they are 2 years old or older they will not and all of your refrigerant will leak out slowly over time.

The service valves are the single most common leak on ANY system.

Originally, they were Shrader valves, but they were not normal tire valves. The material that the seals are made out of was higher quality and can seal at much higher pressures than a standard tire valve. If you have a motorhome that has 100psi tires on it the AC valves are the way to go...

There are many styles of valves now. Make sure you're getting the right ones.

Some KIA/Hyundia valves are slightly different than the normal JIS valves and swapping them damages the valve seats. I ran out of the KIA valves once. Both the Kia and Hyundia dealers didn't have the correct valves and didn't knpw they were different!
I re-used the customer's valves and had to re-do the evac and charge 9 months down the road as the 4-year-old original valves didn't seal properly.

I ate the job and didn't charge the customer again. Full blown come back!
I believe I am the only shop in town that would have done that...

These valves are cheap, replace them every time...

Stop the job if you don't have the right parts or you will get additional training!

[technicalninja]

3rd tip...

Oil balancing is very important!

A modern AC system uses approximately 4 ounces of oil per LB of refrigerant.

Putting too much oil in degrades system efficiency. It coats the inside of the tubing and the heat exchangers and can seriously degrade system heat transfer.

The oil DOES NOT stay in the compressor. It runs around the system with the refrigerant and the liquid refrigerant mixes completely with the oil. When the liquid goes through the phase change from liquid to gas it releases the oil as fine droplets and this oil mist is how the compressor oils.

Ever been in front of a fan with a water mister on it?
This is how the compressor oils...

The ONLY thing that needs the oil is the compressor.
Modern compressors have multiple ways they try to keep the oil in the compressors.
IMO none of them work. I expect 33% of the system oil in the compressor and the other 66% will be in the system, mostly in the evaporator as this is the main area the phase change occurs in.

Most of those expensive refrigerant cans have 3 ounces of oil in them. If you've had an explosive decompression of the system, you might lose 3 ounces. Ripping a hose off is an example of explosive decompression. This vents the entire system charge in a second, you get a BIG bang and a pretty impressive cloud for just a moment.

If you haven't violently vented your system, you NEVER need the amount of oil in one of the fancy cans and putting 3 ounces of oil in a system that needed none is "shooting yourself in the foot."

A slow leak does not vent much of the oil out of the system. You might only need a 1/4 ounce of oil. Experience is what makes me able to determine how much oil to put back in. It's usually a very minor amount...

I have a Hybrid capable machine and it did not have an oil injection system.
At first I was pissed, My 5K machine could not inject oil!
I far prefer it that way now.
I use a 60CC cow injection hypodermic srynge to dispense oil into the high side of the system (ONLY!) during vacuum operations. Work like a charm and was dirt cheap.

Robinair and others make an actual oil injector to allow injection of oil into a charges system. I originally wanted one but after getting used to the cow needle I'm fine with out one.

[technicalninja]

I put oil into the system through the high side port only!
Placing it here means it will be absorbed by the liquid and it will reach the compressor as fine droplets.
It is possible to hydro lock a compressor. We call that "slugging" a compressor.
It doesn't do as much damage as hydro locking a ICE engine but it can destroy the reed valves inside the compressor thus rendering a compressor useless.

Now, when I'm doing a full system and I have everything apart, I place 1/3 of the oil in the compressor sump, 1/3 in the entrance to the condenser and 1/3 in the entrance of the evaporator.

Adding oil to an existing system is ONLY done through the high side port when under vacuum.

[technicalninja]

When replacing a compressor, it is stupid important to rotate the compressor by hand at least 20 360-degree revolutions. This clears the cylinders of oil and keeps the compressor from hydro locking from the start.

If a compressor hydro locks, it sounds like a "mouse with a machine gun".

You get a quick "Brrt" and you're done...

Now, a late modern PWM controlled compressor is at full de-stroke when installed and you cannot really clear them. They add stroke slowly and tend to be self-clearing but I am a creature of habit and rotate them anyways.

Some PWM compressors (German stuff mostly) do not have magnetic clutches and cannot be rotated by hand once the belt is on. I rotate those before I place the drive belt.

[technicalninja]

The very first thing I do when checking a system out is feel the aluminum tubing by hand to see if I have any heat transfer going on.

The high side discharge hose from the compressor to the condenser is the very hottest hose in the system. On a 80 degree day it should be warm-hot, on a 100degree day it will be hot, hot like a cloths iron. Be careful here; this line has the ability to burn you.

The liquid line from condenser to expansion device will still be warm but much cooler than the discharge line. Barely warm on a 80 degree day, warm-hot on a 100 degree day but you should be able to hold on to it without burning your hand.

The low side hose from the evaporator to the compressor (suction line) should be cold/cold.
When working properly it will be similar to grabbing on to an ice cube.

This cold starts from the evaporator and extends down to the compressor.

A slightly low system will have this line getting warmer that closer to the compressor it gets.

We want the liquid refrigerant finishing its phase change at the entrance to the compressor.

The phase change absorbs as much as 100 degrees of temperature and a cold line all the way to the compressor is what we are looking for with one exception.

Late modern systems use a secondary cooler where the liquid line post condenser gets wrapped around the suction line to absorb the extra cooling that is available in the suction line. Suction line post secondary cooler is not cold like the entrance suction to the secondary cooler.

This secondary cooler is old school technology. Mercedes used this set up in the late 70s to cool the return fuel to the fuel tank to reduce evapoatory emissions.

What was once used to cool fuel is now used to cool refrigerant.

These secondary coolers are far more common on R1234yf systems but some late R134a systems have them.

@ClayPerrine This is a item I may try to incorporate into a modern 914 system to do what you have done by adding a secondary condenser. I just need to find a secondary cooler that is long and thin to work in the right side rocker panel where the lines go in a stock ac equipped 914.

This is it for my text barfing for today. I've got to go fix a bunch of ac systems and will be busy...

[VaccaRabite]

Ninja are you going to be offering 914 AC?
Zach

[914werke]

[914_teener]

All good advice.

Not enough though about pulling vaccum and evacuating.

Anytime you open a system you will introduce moisture which is the death off any AC system. It should be evacuated to the specs negative vaccum and then refilled with clean refrigerant as the poster says with the correct amount of oil for the system.

You can rent gauge sets at your local FLAPS.

[VaccaRabite]

This picture confuses me.

Did someone plumb AC.... into a dune buggy?

Zach

[technicalninja]

I'm not finished, just starting. multiple days of information downloading will happen.
I'm just busy working on customer stuff.
Will have multiple posts regarding evac and charge and the need and time for vacuum.

I suck HARDER and LONGER than anyone else I know!

Overnight is common for me...

[914_teener]

This picture confuses me.

Did someone plumb AC.... into a dune buggy?

Zach

Nice catch Zach....I saw a Baja in AZ last week.. with AC. It was 46 degrees outside so I quess they didn't need it that day.

Crank fire as well?

[technicalninja]

Not really planning on offering AC systems for anything.

I will, however, train you all to do it yourself with supply vendor info and all you will need to know...

[mepstein]

Not really planning on offering AC systems for anything.

I will, however, train you all to do it yourself with supply vendor info and all you will need to know...

(IMG:style_emoticons/default/beerchug.gif)

[914werke]

This picture confuses me.
Did someone plumb AC.... into a dune buggy? Zach

Nice catch Zach....I saw a Baja in AZ last week.. with AC. It was 46 degrees outside so I quess they didn't need it that day.
Crank fire as well?

Baja Bug not buggy. & no crankfire you can see the dizzy wires peaking out above the compressor.

[Front yard mechanic]

Looks like a nice set up if you could incorporate a crank fire

[DRPHIL914]

I'm not finished, just starting. multiple days of information downloading will happen.
I'm just busy working on customer stuff.
Will have multiple posts regarding evac and charge and the need and time for vacuum.

I suck HARDER and LONGER than anyone else I know!

Overnight is common for me...

@technicalninja

i was looking back over this because i am looking into AC for the 914 its hot here and humid in SC just like Texas, and i am wondering what you think of using the new electric compressors, this is the direction id like to go, AND i would like to not put a hole in the front trunk so what options would i have for a small system and more compact stuff- nost sure what the call it the evaporator coil finned thing was under the floor board of front trunk, so looking for system design suggestions.

Phil

[technicalninja]

I'm running 14-16 hour days right now, 7 days a week. Customers get down right demanding when the temps are above 100...

Units that take the hot high-pressure gas from the compressor and condense it down to a high-pressure cooler liquid are called condensers.

There is no real downside to running excessively sized condensers (or dual) except weight and the requirement of more refrigerant.

Units that allow the high-pressure liquid to evaporate (rapidly) and absorb heat are called evaporators. Once again, bigger is usually better.

Being large on condenser has a larger effect on efficiency than being large on evap.

Both units are technically heat exchangers.

I'm planning on making a fiberglass 916 style front cap that gives me enough room to install a wide thin core in the bumper and NOT use the normal location, but I haven't finalized anything yet.

Clay suggested another condenser trick that I may employ. Running a small condenser inside the engine compartment ala 911 style condenser in series with a front cooler.

This will most likely KICK ASS!.

When using cheap condensers, I commonly have to correct warpage before install (make them flat) and I believe I will be able to bend a new core to the same arc as the front bumper. I haven't tried this yet, but condensers can take a bunch of straightening and not leak.

I do apologize on not finishing out this thread but what I really need to do is a series of you tube vids explaining automotive AC systems and post them on my website.
This is something I'm going to try and get done in my next slow season.

On electric compressors...
The Mitsubishi electronic compressors work extremely well but require the 600 volt battery pack to function. (Toyota Prius/Cadillac hybrid Escalade) This is too heavy and bulky for a 914. The Cadillac unit is actually mounted on the fender well and not built into the engine like the Prius one.

Clay's unit is straight 12 volt and if it works as it's supposed to it may well be the answer for our 914s.
It will require a Billy bad-assed charging system and maybe a bigger battery.
I haven't seen the unit Clay Perrine is going to use but I am very hopeful it will suffice.

One nice thing about the 914 is the tiny passenger compartment. It is half the size of a standard economy car and this makes it a butt-load easier to cool off.
Smaller parts should work well.

I've helped many Fieros turn into refrigerated meat transport vehicles.
They have tiny cabins as well and run R12.

I actually have a "spec' for the final unit in my car.
I want it to freeze my ass off on a 100 degree day, with the top OFF!
I'll be shooting for 33-34 degree vents on high blower...

[Steve]

I'm running 14-16 hour days right now, 7 days a week. Customers get down right demanding when the temps are above 100...

Units that take the hot high-pressure gas from the compressor and condense it down to a high-pressure cooler liquid are called condensers.

There is no real downside to running excessively sized condensers (or dual) except weight and the requirement of more refrigerant.

Units that allow the high-pressure liquid to evaporate (rapidly) and absorb heat are called evaporators. Once again, bigger is usually better.

Being large on condenser has a larger effect on efficiency than being large on evap.

Both units are technically heat exchangers.

I'm planning on making a fiberglass 916 style front cap that gives me enough room to install a wide thin core in the bumper and NOT use the normal location, but I haven't finalized anything yet.

Clay suggested another condenser trick that I may employ. Running a small condenser inside the engine compartment ala 911 style condenser in series with a front cooler.

This will most likely KICK ASS!.

When using cheap condensers, I commonly have to correct warpage before install (make them flat) and I believe I will be able to bend a new core to the same arc as the front bumper. I haven't tried this yet, but condensers can take a bunch of straightening and not leak.

I do apologize on not finishing out this thread but what I really need to do is a series of you tube vids explaining automotive AC systems and post them on my website.
This is something I'm going to try and get done in my next slow season.

On electric compressors...
The Mitsubishi electronic compressors work extremely well but require the 600 volt battery pack to function. (Toyota Prius/Cadillac hybrid Escalade) This is too heavy and bulky for a 914. The Cadillac unit is actually mounted on the fender well and not built into the engine like the Prius one.

Clay's unit is straight 12 volt and if it works as it's supposed to it may well be the answer for our 914s.
It will require a Billy bad-assed charging system and maybe a bigger battery.
I haven't seen the unit Clay Perrine is going to use but I am very hopeful it will suffice.

One nice thing about the 914 is the tiny passenger compartment. It is half the size of a standard economy car and this makes it a butt-load easier to cool off.
Smaller parts should work well.

I've helped many Fieros turn into refrigerated meat transport vehicles.
They have tiny cabins as well and run R12.

I actually have a "spec' for the final unit in my car.
I want it to freeze my ass off on a 100 degree day, with the top OFF!
I'll be shooting for 33-34 degree vents on high blower...

I’m running the benling dm18a7 12v compressor. Draws 60amps at the medium setting. More than enough for our little cockpits.

https://benling.coowor.com/shop/product-det...09087VFAMP1.htm