Air conditioning rant and a few questions

Charged the system tonight. I was 2 oz shy but I was getting no cooling. Pressures were 20/75, but there was no hunting that I was experiencing before. Both pressures were low, just like the last time I partially charged, but my high side is now lower.

Remember I said that I lost all cooling when I last changed the TXV, and I said it was pretty coincidental? I'm now wondering if I received another junk valve. I wasn't spending much, and these were China valves.

I'm thinking that I should order an O.E. valve and see what happens before I blame and pull the compressor again. Opinions?

I think Rein is the O.E. valve; can anybody confirm? I'm hoping the Denso wasn't returned erroneously.

-Todd

Rein is the manufacturer of the TXV I have presently installed.

If you are suspecting a poor quality TXV, I would change it.

Tony

Is Rein O.E. or at least O.EM.?

Thanks.

-Todd

Denso 471-7000 shown in stock at Amazon for $335. I returned two allegedly new Sanden compressors when they showed up from China and installed a 4 seasons rebuild. It has worked fine for a year now but who knows how much longer? Your pics sure look like an item that was installed/removed/returned.

Todd,

Your compressor was backordered from the manufacturer and you ended up with a unit manufactured in 2007 (at least the label in the pic indicates this)?!?!?!

Looks like this is a unit that has sat on a shelf for 5 years. Also, if it was backordered I would expect to receive the actual brand of compressor you had ordered. If it was backordered you would think the manufacturer should beshipping newly manufactured units.

Something fishy is going on with your order.

I saw that Amazon had it in stock, but I wanted a local vendor in case of a warranty claim. Denso is based in CA and I'm in NJ. If there was an issue, I'm sure I'd have to ship it to them, wait and see if they'd stand behind their product, then have it shipped back. I figure 3 weeks.

If I wanted the Driveworks compressor, I could have had it the next day. Returning the Denso was absolutely hassle free. Including my credit card benefit, I have a 3 year warranty.

The compressor wasn't back ordered. Advance Auto's site had none in stock. Apparently, they don't share stock with the stores. When I originally called for a replacement Denso, they offered me the Tough One. I declined, then called back the next day and was told "out of stock". They ordered 2 more in; I just had to wait for the site to show availability.

The local store told me rebranding/reboxing was common when a part wasn't available, especially on older car parts. Other than the greasy fingerprints and the torn sticker, this compressor shows no signs of scratches, peeling paint, corrosion, etc. The threaded bushings that compress to the bracket were fully retracted. The oil looked perfect. If someone were to have gone through all the trouble to hide use, I figure they would have wiped the outside down, and removed the torn sticker.

Anyhow, I called GAP this morning for the TXV. They carry CRP (Continental). I asked about Rein and he told me they were a rebrander and wasn't sure who they got them from. I asked about O.E. and he said TGK. They don't stock them, but could get them for about $50. I went ahead and ordered the TGK.

I'm still hoping for the best and will recharge once my new TXV comes in... I just want this to work. As mentioned, the local store manager will replace all my oil and refrigerant if the unit proves to be bad. He told me I'd be better off ordering another online, because he can't match the discount and his district stores don't show availability.

-Todd

The TXV was sitting on my doorstep when I got home from work. It was around 80°, so I wanted to get it swapped and start the vacuum.






Of course there's always an issue and it started as a leak when the port valves were closed. I go to tighten the 5mm bolts and one strips the hole.

I run around to a few stores looking for a Heli-coil and of course nobody stocks one that small. I go to Home Depot and find that 10-32 thread pitch is a near perfect match. Apparently the stock bolts don't go all the way through the backing clamp, and I'm able to catch a few threads but I still use a lock washer and nut. Not the worst glitch; I'll get another clamp the next time I'm at the junkyard.

The system ends up holding vacuum for an hour after vacuuming for an hour. I also heated the drier for good measure. This drier has been exposed to air for at least an hour, over the last few troubleshooting sessions.

Time to charge. Charged as a liquid through the high side under vacuum and the pressures are at 22/100 with the first can and I'm already feeling cold air. It's already higher than last time with a near full charge. The second can takes me to 32/180 and I still need to add 5oz.

After adding 27 oz total, I'm seeing 55° at the vents on max/recirculate. Pressures are at 32/185. Wondering if this is anything like propane I take it to 1,750 rpm and only see around 50° with a 72° ambient. It's not propane cold, but this point, I'm not complaining! I figure if it's at least as good as 134a, I'll be happy for now.

So onto my new alternate refrigerant.... computer duster aka R152a.

Where I first read about it:
http://www.rx7club.com/2nd-generati...sy-cheap-safe-alternative-refrigerant-964688/

MSDS of the product that I used... take note of the manufacturer:
http://www.sisweb.com/referenc/msds/dustoff.pdf

GM/Delphi tests. Plenty more of these online:
http://www.sae.org/events/aars/2002/baker.pdf

I bought a 6 pack of "Dust Off" from Costco for under $20. Using the conversion, I needed 27 oz of 152a compared to 42 oz of 134a. $20 gets me almost 3 full charges. I figured if it didn't work out, I'd just huff the stuff. That's what all he cool kids are doing!










At this point, I'm claiming sucess and will be celebrating with beer and whiskey. Now, I just need my China compressor to hold up. If this goes well, I may upgrade to a large parallel flow condenser, later on.

-Todd

Good job to come up with this, although I bet you broke about a dozen useless laws when you did this the way you did......maybe you should re-word your posts to state that this is for experimental purposes only

It is a shame that the ac industry as a whole has done everything it could to spread misinformation when it comes to what is safe and will work in what application. Most of what I know on what can replace what was learned in the real world in the late 80s to early 90s from retrofitting farm ac and cooler systems. We are surrounded by stuff in cans of all sorts that will work as drop in replecement in most ac systems, it is a shame that this knowledge isn't out there......

One thing I would do is create warning under the hood that state's that the refrigerant has been replaced with R152a.

On test performance, I looked up the numbers and they are pretty close to R-134a but less quantity being required for the charge. It does seems that it is miscible with factory oil the same as R-134a, this stuff is not miscible with mineral oil so could not be used as a drop in replacement for CFCs. It does look like the cooling in side by side is a little better than R-134a but close from what I read a little while ago. I remember this being talked about years ago as the stuff we would use the replace CFCs. You have me wanting to did through some of my college papers now......

Let us know what the cooling numbers you see are in higher humidity and heat, I seem to remember this stuff having some over expansion issues from high ambient heat events( becoming unstable at very high ambient temps to the point of causing a system over pressure & release )......

Ha!... the word experimental was in there, but I deleted them because I wasn't the pioneer.

"Useless" is the correct term once you realize that other "dusters" are 134a or paint ball propellants, etc, (and are legally vented) but more people want comfort than skirmish. Before I went on this kick, I knew dusters were also 134a, but never considered a side can tap to get them into my car.

I'll report back, once the temperatures start climbing again. This stuff's COP is supposed to be better with a higher ambient temperature.

-Todd

90° ambient with 50% humidity, today.

I was seeing 58°-60° on max/recirculate at idle. At around 2,000rpm, I was seeing around 55°.

On speed 2, I was seeing around 45°, so that's not terrible, but I was hoping for better.

All in all, I think it's working. One thing I notice is that it seems to take slightly longer for the vent temps to bottom out. With propane, the cold air was almost immediate.

-Todd

Todd,
Your temps are not too different from mine.

>90F on the freeway, hi speed, vent temp is ~53F; < speed 2, vent temp is ~45-47F
>90F in town, high speed, vent temp will be 53-56F; < speed 2, vent temp is ~45-47F

<90F, freeway or in town, <=50F at high speed. Low speed (1 or 2) will be <45F

Tony

Tony, I was hoping for better based on the info that's out there. Supposedly, this is a superior refrigerant. Oh well, I guess I'm in the ballpark, so I can't complain. Maybe a mix of duster and propane is in my future...?

Thanks for all the input along the way.

Anyhow, I went back through the thread. The last TXV swapped on 6/30 was obviously bad. The Denso I returned may have been good, and I may have suffered for over 2 weeks over nothing but a cheap China TXV.

I contacted the company that sold me the valve and they promptly refunded my money.

-Todd

Todd,
You bet!

It's all in the name of learning, anyway!

Tony

From what I know your numbers are in line with what that refrigerant can produce, about ~3* F lower @ the vent than would be seen with R134a.......

Propane will work but it has issues with lubricant miscibility, straight propane is not the best at moving the lubricant around the ac system so will shorten compressor life. You might try mixing in a ~20-30 % of total quantity charge of one of the hydrocarbon blends like R-12a or R-22a, I use Redtek. This stuff is specifically blended for better miscibility so has a better profile of being miscible with your refrigerant oil than straight propane......

Also, You can't use a 100 % charge of either in your car without adjusting the evaporator bleed down pressures, R134a spec range is too high to cool down without the system being overcharged. But you can mix them to keep bleed down pressures at the low end of spec within spec and still keep the charge quantity within spec.

A mix of one of the HC blends in the 20-30 % of total charge will allow you to still get the extra cooling into the ~20s * @ the vents. I have documented temps as low as the high 10s* F @ the vent in A4s & A5s Jettas/Golfs/NBs and in B4s & B5s Passats with that blend. This blend works the best in cars without cold temp shutoffs like VW & Audi ac systems. In cars with low pressure shutoffs like my Honda & Toyota the set bleed down profile cause no cooling in higher ambient temps. On cars that have a low pressure/temp cutoff it is hit and miss on whether a blend will achieve colder temps. In these cars if you get the blend & too high it will lower the bleeddown spec to be out side what the system's factory range spec will allow negating any extra cooling you would see...

On VWs & Audis with the varible displacement compressor I have been forced to install a cold shut off switch in our cars to prevent freeze up in higher humidities.....

I have had really good luck with these over the years in all sorts of auto ac systems....


good luck.....

Ah, not so fast, lol. Today was around 95° and I was seeing anywhere from 45-52° on speed 2. It was good, but like a typical American, I wanted more!

I was running some errands after work, ambient was now 90° and im seeing the same vent temps. On max/recirculate I'm seeing 60° and my pressures are 35/235. I don't feel like evacuating and pulling another vacuum, so I decide to charge by pressure. I bleed down to 28/165 and now I'm seeing 64°.

I hook up the propane rig and I start charging. I planned on charging to the original spec, but I slightly overcharged. I'm now at 42/240. I'll take care of that later. Onto the pics.... don't mind the CEL. It goes on and off ever since I advanced timing to max as suggested. I need to retard a bit.

I dropped around 8.5° on max/recirculate.




Speed 2@ idle.




Speed 2 after holding it @ 1,750 rpm for a minute. MWUHAHAHA!




On straight propane, I saw as low as 21°!

Would you need an adjustable TXV to control bleed down? AC tech at work mentioned something like that a few months back. He's the same guy who got me charging as a liquid.

What's involved with installing a cold pressure switch? I'm guessing without it, the evaporator freezes? I was just planning on dialing the temperature knob back.

Thanks for any info that you can or have supplied.

-Todd

ToddA1 said:

Hey, Rotary kid.... where'd your post go?

-Todd

Click to expand...

On what is involved with getting and installing a cold cutoff,

I just had someone at the local auto zone/napa/ect... take me to the shelves where all the factory cold cutoff switches are to pick one that fits the bill. Look for one that is adjustable, one that has a small screw tha can be moved to adjust the cutoff temp.

Then take a drill bit with a wad of electrical tape wrapped around it 1/16 or 1/32" above the end to make a depth gauge on the drill bit to prevent drilling too deep. Then feed the tubing into the evaporator case until it is touching the coil. Insulate the rest of the tubing sticking out of the case and mount the mechanical part somewhere. Cut/splice into the switch wire that goes to the ac on & off switch, install the cutoff switch. Run the ac system and adjust the spring tension as needed to set the cutoff for desired temp..

Geez, the evaporators are buried in these cars. I've been seeing a lot of foam in my vents, so the dash needs to come out soon. Maybe I'll do it then, if at all.

I'm hoping the sensing tube is long enough that the mechanical switch can be mounted somewhere other than behind the dash? So, that it an be adjusted without necessitating dash removal?

-Todd

ToddA1 said:

Geez, the evaporators are buried in these cars. I've been seeing a lot of foam in my vents, so the dash needs to come out soon. Maybe I'll do it then, if at all.

I'm hoping the sensing tube is long enough that the mechanical switch can be mounted somewhere other than behind the dash? So, that it an be adjusted without necessitating dash removal?

-Todd

Click to expand...

On your car you can get the access you need from under the dash, without removing a lot of stuff. I have done this to several 97 Passats over the years. It's not fun sitting on your head for a while but it can be done. From memory you just remove the Knee bar along with the center console.

My car is somewhere else right now, on the other end of the US so I can't take pics but the removal of parts in the area will give you all the access you require to do this.

I am stuck in my Honda right now so haven't had the Passat in front of me for a while so can't recall if the B4s has a glovebox, I've got the layout of my Accord stuck in my head right now. But if the B4 Passat does have a glovebox you have a straight shot to the evaporator area when removed. The A4s allow a pretty straight forward access through the glovebox hole to the area. The point is that you can do this without tearing the dash appart.....

good luck

I did some research on the low temp cut off switch. I would guess that it's nothing more than a normally closed thermo switch and the adjustment screw would open or close the contact distance. Do the leads simply break the 12v line to the clutch?

Anyhow, last night I bled off the system so the low side was back to 35 lbs. Cooling suffered marginally, but only by 2 or 3°.

Today was 94° with 55% avg humidity. I didn't have time to check all speeds, but speed 2 was in the high 30s at cruising rpm and settled in the mid 40s at idle. I'm happy.

I did a lot of stop and go traffic after work and was pretty much seeing mid 40s. About an hour in, I notice the temperatures are slowly creeping up. At the end, I'm seeing 60° and have been having a heavy fog coming from the vents. I figure maybe the system built too much pressure, and the safety valve opened. I shut it off, then back on and the same continues.... I leave it on.

A storm rolls through, the temperature drops and the rain starts. Both pressures should be plummeting. No change in the vent temperature. 20 minutes later, the vent temps are dropping. Speed 2 doesn't get any lower than 50°.

It's cool out, so I turn the system off. 15 minutes later, I turn it back on and the vent temps are back to normal. I'm cruising for a while and I'm seeing 26° and it's a meat locker in the car. I shut the car off and get something to eat.

On the way home the system is working fine. Just as I pull into the driveway the heavy fog is back. I hook up the gauges and I'm seeing 22/210. Grab a partial can of duster and load the rest into the system. I figure about 6 oz, which equals around 9.3 oz of 134a. Close the valve, let the system settle and I'm seeing the same 22/210. Vent temp on 2 is 52°... I should be around 40°.

I leave the gauges hooked up; I want to see the static pressures in the am when totally cold, to see the possibility that I'm undercharged. This morning I saw 120 lbs.

Good times.

-Todd

77° ambient with 85% humidity. Static pressure is around 120lbs, which is good.

Start the car and the pressures stabilize at 45/250, so I bleed off until the pressures are back to 35/225.

Cooling is pretty much back to normal, but I'm doing quick tests as I'm late for work. On speed 2, I'm seeing 41° and I saw as low as 34° cruising. I'll attribute the loss of cooling because propane was bled off.

Not sure what to make of last night (fingers crossed), but one thing that I want to do is adjust the pressures when I have higher ambient temperatures.

I Googled the fogging and saw it was normal on very humid days.

-Todd

There is never a dull moment, is there?

Check your clutch coil current, when you first switch on, and compare it to when the AC quits working. I had a coil that worked fine for the first summer, then at the start of the 2nd summer, it would increase in resistance with temperature. Such that, at operating temperature, it would draw enough current to stay engaged. But, after a stop-start cycle, like a convenience store stop, it wouldn't have the field strength to engage. Yet, on a cold (ambient temp) start, or sitting for more than 90 minutes or so, it would operate normal again.

Tony

Thanks for the idea but the system never stopped cooling; it just didn't cool as well. The compressor hub never stopped spinning.

89° and I'm seeing 42° at idle and 37° cruising on speed 2. I'm at a loss. I guess it's something that I'll have to keep my eye on.

-Todd

Wait.....

You're saying your inner hub was spinning but the clutch wasn't fully engaged? Is that possible?

-Todd

ToddA1 said:

I did some research on the low temp cut off switch. I would guess that it's nothing more than a normally closed thermo switch and the adjustment screw would open or close the contact distance. Do the leads simply break the 12v line to the clutch?

Anyhow, last night I bled off the system so the low side was back to 35 lbs. Cooling suffered marginally, but only by 2 or 3°.

Today was 94° with 55% avg humidity. I didn't have time to check all speeds, but speed 2 was in the high 30s at cruising rpm and settled in the mid 40s at idle. I'm happy.

I did a lot of stop and go traffic after work and was pretty much seeing mid 40s. About an hour in, I notice the temperatures are slowly creeping up. At the end, I'm seeing 60° and have been having a heavy fog coming from the vents. I figure maybe the system built too much pressure, and the safety valve opened. I shut it off, then back on and the same continues.... I leave it on.

A storm rolls through, the temperature drops and the rain starts. Both pressures should be plummeting. No change in the vent temperature. 20 minutes later, the vent temps are dropping. Speed 2 doesn't get any lower than 50°.

It's cool out, so I turn the system off. 15 minutes later, I turn it back on and the vent temps are back to normal. I'm cruising for a while and I'm seeing 26° and it's a meat locker in the car. I shut the car off and get something to eat.

On the way home the system is working fine. Just as I pull into the driveway the heavy fog is back. I hook up the gauges and I'm seeing 22/210. Grab a partial can of duster and load the rest into the system. I figure about 6 oz, which equals around 9.3 oz of 134a. Close the valve, let the system settle and I'm seeing the same 22/210. Vent temp on 2 is 52°... I should be around 40°.

I leave the gauges hooked up; I want to see the static pressures in the am when totally cold, to see the possibility that I'm undercharged. This morning I saw 120 lbs.

Good times.

-Todd

Click to expand...

Maybe the evap iced up? Shutting it down for a while then getting 26* when you turn it back on would seem to indicate that.

On the static pressure, I think you know this but all that tells you is that you have some liquid. You could be drastically undercharged and still have good static pressure.

ToddA1 said:

You're saying your inner hub was spinning but the clutch wasn't fully engaged?

Click to expand...

Not quite...the magnetic field was weak, such that the clutch would stay engaged, but did not have enough field strength to engage the clutch when power was applied a short time later.

KLXD said:

Maybe the evap iced up? Shutting it down for a while then getting 26* when you turn it back on would seem to indicate that.

Click to expand...

That makes sense to me.

KLXD said:

On the static pressure, I think you know this but all that tells you is that you have some liquid. You could be drastically undercharged and still have good static pressure.

Click to expand...

Agreed!

Tony

KLXD said:

Maybe the evap iced up? Shutting it down for a while then getting 26* when you turn it back on would seem to indicate that.

Click to expand...

That could possibly explain it, but I was seeing 40°s and the temperature was creeping upward. Then the cool air plateaued in the 60°s. Now if I was constantly cruising at 26° and then I lost cooling, that would be my thought.

Funny, but since I've had all these issues, the vent thermometer is always on. I monitor it like a critical gauge.

KLXD said:

On the static pressure, I think you know this but all that tells you is that you have some liquid. You could be drastically undercharged and still have good static pressure.

Click to expand...

I honestly wasn't aware of this. I'm learning as I go. I figured I know what the pressure was when I charged by weight. The ambient temperature was about the same, so I figured the static pressure would be about the same if my charge was correct.

I notice when charging that liquid can be flowing, but low/high pressure may be the same after the system balances out.

The system seems to be working fine, since last Thursday. I was seeing 35° cruising on 2. Ambient was in the high 80°s with 80% humidity today. Idle temperature on 2 was just under 50°.

It appears that difluoroethane is like propane with its lower efficiency at idle speeds.

-Todd

I had a similar AC issue recently in my B4V. It has been ICE cold for 3+ years, vent temps of <50 on speed 4 and <35 on speed 1. Best AC I ever had, it would literally freeze your hands/arms.
Then I the car sat parked for 10 days over 4th July, and when I drove it again, vent temp didn't want to get below 55/60.
Pressures were about right, about 35/200 cycling to 40/190 in 90 ambient.
I added about 8oz thinking it was low, but all that happened was the LP rose a bit more.

After doing some research I found these Sanden SD7V16 compressors are variable displacement, and the control valve is apparently prone to sticking.
So, I bought a new control valve for $22. Fitted it last night, pretty easy, remove compressor, open head on the bench.
Recharged, and I am back to 20/240 as pressures, and <35 at the vents on speed 1.
I guess it gets stuck at mid displacement, and never gets the LP low enough ??
Not sure if that is your issue, but thought I would offer it up.

I hope not, I'm running a new, albeit Chinese compressor.

That control valve was one of my troubleshooting steps in my original compressor.

-Todd

That is a characteristic of just about any AC system and any gas that is stored as a liquid in a pressurized bottle like CO2 or propane.

If you start with the bottle at 0 psi absolute or vacuum and you start adding the gas, the pressure will increase to the saturation pressure of that gas which is dependent on the temp. About 110 for 134a at ambient temp I believe.

At that point the gas starts to condense. The pressure will stay the same (if you do it slowly enough for the temp to stay constant) until the bottle is completely filled with liquid. At that point the pressure will start to rise again.

So at a given temp, as long as there is a drop of liquid, the pressure will be the same as if it were completely full. You can't tell how much liquid is in there.

This is why a CO2 bottle is filled by weight. Also why a pressure gauge is pretty much useless on a BBQ tank. Once you start to see a pressure drop on your BBQ tank you don't have much gas left.

I prefer charcoal.