Automotive Air Conditioning Information Forum

Hey, I’ll try to get a photo when I’m back in town but the TXV does have some very faint lettering on it that says 1.5t r134a. Also, when I bought the evap unit it specified that it came with a 1.5t TXV.

None of the lines come anywhere near anything hot, I’m afraid. Maybe you can see in my really early photos that the lines come straight forward from the compressor, which is mounted on the top front of my v8. Nothing hot except hot ambient underhood air — and due to the shrouded nature of the van, the underhood area is very hot.

As far as the kinking, I am assuming that is ruled out due to the low (5psi) pressure drop I was able to measure using the two low side service ports. One at one end of the low side hose, and one at the other. I was told that 5psi drop was nothing, and that even a #12 hose wouldn’t help.

To me, based on what I’m learning thus far, my uneducated hunch is the TXV needs to flow more and I need to give it a bigger charge. But we will see what the pros say!

It's not that a #12 hose wouldn't help, it would. It would make the system perform slightly better. But 5 psi pressure drop is great, if I saw that much drop in a current program I would think it's just fine. I can't recommend all the extra work and cost for you just to get maybe 2 psi better.

I think you overcharged it this last time, seems like correct charge for the system in it's current state is 36.6 oz you had 20F subcool at that charge. When you get the TXV to flow properly, it will need to be a bit higher since there will be more liquid in the evap, but this is a small amount.

When you get back to working on the van, please check temperature of the condenser out, receiver out, TXV in liquid lines. A plugged filter or screen or a kink has the same system effect as a TXV that isn't opening except a plug is easy to find, you'll detect a temperature change right after the restriction.

Howdy folks. Me again! I finally got some time to get back to it/

I replace the TXV with a new one from ACDelco. Certainly looks nicer than the one that came with my unit.
The "BOWEI" unit is the original, you can see it says 1.5T on it.
The new unit is rated at 1.5t as well, but doesnt say so on the actual txv body.




Charged it up tonight, you can view my latest data here:
https://quick-jodhpur-b87.notion.site/C ... a2771f02d1

Got vent temps down to 52F in 84F weather with 45% humidity—which is better that usual, but not as cold as I'd like to see.

In the chart, you can see the additional temp readings i got that Detroit was looking for.

Looking like 27* of subcool, 47* of superheat.

Interesting, have never seen the tonnage rating stamped on a TXV, which frankly, they should always do IMO.
Now as to the charts: much better arranged.
Look carefully at the values of the pipes in and out of the condenser.
Study closely. Something is radically wrong with your condensing.....condenser plumbed backwards, no airflow, clogged (inside or outside or both) , something. Thread is too long for me to go back over all this.
The best your condenser is doing is a 9F differential. At your final fill value, there is NO differential.
The differential is a number that should be at least 25F or better still 30F. ANY finned coil should be able to drop the incoming temp by 30F.
Your car's radiator does, the condenser on your outdoor AC resi unit does, and a properly functioning mobile condenser also does.

Review what the condenser does.
Where does the heat in an AC system come from?
1) heat absorbed by the evap in the car cabin.
2) heat of compression of the vapor in the pump. The pump takes low pressure vapor and compresses it to high pressure vapor.
3) heat generated by the moving parts of the pump itself.

All that heat has to be given up to the atmosphere in order to change the 134 vapor (gas) back to liquid to present to the TXV to start the process all over again. That is the job of the condenser. The TXV MUST have what is termed a solid column of LIQUID 134 presented to it. No wonder your superheat is so high (should be about 10).

At your final fill level (the last line of the table) there is no differential at all, meaning your condenser is doing NOTHING, ie not removing any heat, ie NOT condensing the vapor to a liquid. I am truly amazed that you can even get a vent of 52F

Review of superheat from the MACS website:
https://macsmobileairclimate.org/2021/1 ... superheat/

Subcooling:
https://en.wikipedia.org/wiki/Subcooling

Damn, yeah that is pretty crazy huh. Thanks for pointing that out!

Seems very weird. I'm going to make 100% sure of my temp readings at the condenser-in and -out lines. The out line (at the bottom) was shiny metal, I just shot some flat black paint on it so to be sure my IR gun isn't giving me a false reading. The in line was already covered in flat black paint.

Assuming my readings are correct, what's my next course of action? Ensure proper airflow from my fan, and possibly replace my condenser?

Isn't it a bit weird that it drops another 18F after the drier?

Also, what if, possible, the condenser-in temp should just be higher, rather than the condenser-out temps? Weird idea, but 120F doesn't seem that high to me, especially under the hood of a running van on a hot day, and near a radiator...

As you stated, be sure of your readings. Agree with the flat black on the shiny pipe.
A temp drop after the drier suggests the drier is clogged.

Calibrate your temp gun. Boil water in a dark mug and shoot to see if you get 212.

Did you ever do the water hose over the condenser test?
And 84° is not all that hot, so yes you need better than 52F at vent.

Something is goofed up. Wish I could be standing right there.

Did the prev. comp grenade at some point and leave debris in the condenser and drier? If so, both should have been changed out and lines flushed.

When you removed the previous TXV, did it have a filter screen and if so was there any debris at all on it?

I went back and read the ist post. SO you installed a single-unit under-dash system, correct?

that's correct, Tim.

T-Bird: All the stuff is new. New compressor, new lines, new condenser, new drier, new binary switch, new evap, new txv, etc, etc. Nothing grenaded and there is no debris. No filter in the TXV and no debris seen anywhere.

IMO, you will never get it to cool with a single system. Just too much volume of air to cool enough. Many have hung curtains or the freezer vinal behind the seats to reduce the volume.