Installing Aftermarket AC in a Dodge Van

[GottaBeCold88]

Okay, update. I finally got a shop to recover my refrigerant.




Looks like I had over 2.6lbs of r134a in there.





Next step is to drain the compressor and refill it.

Then another attempt at recharging.

[tbirdtbird]

Thanks for writing.
Please keep us posted

[GottaBeCold88]

Ok folks, updates.

First of all, I pulled my compressor and drained it of oil.

I turned it upside down and turned and turned on the crankshaft and only a little less than an ounce came out. Kind of weird.

I was able to add in 4.5oz of new pag oil, no problem.

After I bolted it back in, I drew a vacuum and held it overnight. Today, I worked on charging it.

It was extremely hot today, about 100* and 35% humidity.

I did ti all while holding the throttle open to 1400 rpm.

Here are my results. I ended up putting in 37.9 oz of r134a. Coldest I could get the vent temps to was 57*.

I thought I was recording suction and discharge temps but I realized at the end I was doing it wrong. So I only have suction and discharge temps for the final charge amount.

You'll see at the end, I sprayed the condenser with a garden hose and the pressure dropped significantly. I was wondering if this would point to a lack of proper airflow. I did order a 16" fan from SPAL to replace my 14" no-name brand fan, so that'll be going in. Maybe it'll help.



Ater the garden spray at the end, I let it run for sveral more minutes and it seemed to reach a settle pressure on high and low. My final results at 100* ambient, 35% humidity were:
Low: 30 // High: 160 // Vent Temp: 57* // Suction Temp: 71* // Discharge Temp: 115*

Wondering if I should still add more, or what?

[tbirdtbird]

That is 2.3 LBS.
I would not add any more until John or someone gets back. Due to the custom nature of your project, you are over my pay grade, but the numbers need to be better.

As far as a condenser goes, there is no such thing as too much condenser or too much fan. The condenser is giving the heat of your van back to the atmosphere, it is your best friend

[DetroitAC]

Nice, you should add more, but only in tiny increments (like 1 oz at a time). i think when you say discharge temp you are measuring condenser outlet, and the temperature there is showing basically zero subcooling, so it makes perfect sense. I think you're somewhere in the process of filling up the receiver, but i could be wrong about that, so add charge in small increments.

Your condenser and it's airflow are just fine, pressure is very low, you will get a performance boost by charging more and getting some subcooling. You can Google R-134a pressure chart and find one with values for every degree Fahrenheit, I found one by searching for "R-134a Pressure Chart Refrigerant Guys", nice table has values every 1F.

I would suggest keep measuring the way you are, charge until you hit 20F subcooling. you will see no change in anything until the receiver gets filled, then every additional increment of charge will cause your condenser outlet Temperature value measured to be colder than the Saturation temperature shown on the PT chart. You have to add charge, record pressure, record temperature, look at the chart and find your pressure if for example your pressure is 200 psig, you find the closest pressure value (might be 198, might be 202, whatever), and look at the corresponding saturation temperature in the PT chart (131 F). If your actual measured temperature of the condenser outlet is 121F, means you have 10F subcooling. If your saturation temperature is 131F and your actual is 111F, you have 20F subcooling.

You have to look at the table with every charge increment added, condenser pressure goes up with every increment because the very last bits of condenser tubes are filling up with liquid. This is fine, your condenser size and airflow are great from what I can see.

Your suction temperature is a problem, way too warm, TXV maybe isn't flowing enough refrigerant to fill the coil, part of the coil is running warm. Can you get the pipe temperature close to the evaporator exit?

If the high suction superheat is due to suction hose just gathering heat, insulating might help, but you might not be able to in the A-pillar.

If it's warm coming out of the evap, Adjusting the TXV superheat bias screw would get you more performance, it's buried inside the fitting that is inline with the TXV stem and charge head. The dome on top houses a metal diaphragm with a valve stem, bias screw is reached by taking off your hose fitting, not sure if that's accessible or if you are up for that. It would be a time consuming process of recover, open the fitting, adjust the screw a bit (probably it's an internal hex, so Allen wrench), evacuate, recharge.

Edit: don't adjust the TXV until the charge is correct, it'll get closer to correct when the charge is correct

[GottaBeCold88]

Okay sweet! I will add more.

Question, where should I be measuring temps for the superheat and the subcool stuff?

So far I have been measuring the outlet at the bottom of the condenser for the hot side, and the fitting on the compressor for the cold side.

But, I could measure one of the fittings at the back of the evap unit. I feel like the fitting on the compressor is suffering from heat soak potentially, and maybe reading higher than it should? Perhaps the evap exit would be a more accurate reading.

I want 20F of subcool, but how much superheat?

[DetroitAC]

I think you are measuring in the correct place for the high side.
On the low side you don't really have a choice but to measure the pressure and temperature at the same location, doesn't need to be exact same, but close. Suction hose always has big pressure drops, yours is probably very big due to longer hose and it is #10. Measure suction pipe temperature right where the low side pressure is measured.

If you could also measure at the evap exit it would help, but you may not have that many thermometers or thermocouples.

20F subcool is probably what you want, i can't be sure, don't really know how your condenser will behave but that's my educated guess, and the number that most modern systems end up at to optimize performance.

I would shoot for 10F superheat at the compressor suction, again I'm not sure, you may have to have liquid exiting the evap to do that since the suction hose run is so long, and I wouldn't advise that.

I would suggest add charge in small increments to hit 20 subcool and see how things are.

[tbirdtbird]

Detroit, (or John)

I may have to adjust the bias screw on a 1 ton TXV at some point in the future.
Is there any relationship to the number of turns of the screw (CCW) and degrees of lowering superheat? Even a wild a** guess would help.
Like maybe 1/4 turn CCW is equal to 5°drop of superheat?

With this current project, a #12 hose up the A pillar would have been nice, had there been room

[GottaBeCold88]

Ok cool, sounds good.

Also, I think I could probably fit a reduced barrier #12 hose in the a-pillar. If it's worth it, maybe if I end up having to recover and recharge I could change this hose.

[DetroitAC]

My feeling is 1/4 turn is about 2 K superheat change so ~ 4F superheat change, so yeah we have same guesstimate. Every TXV can have different bias screw pitch and spring force. Yes, Usually CCW is less superheat, more flow.