A/C charging issue resolved.

[brokencase]

A while back I replaced the A/C compressor in the Scorpio. It went in OK. The system was evacuated and held a good vacuum.

However I could not get the system to accept a charge. The compressor clutch would not activate. Connect the refrigerant to the low side and other than filling the line, the can would not empty.

I though maybe the low side Schrader valve was blocked.

Frustrated, I decided to back burner the project for a season. To many other things to deal with at the time.

It was starting to get warm outside so I decided to tackle it again today.

First, I decided to de-press the low side Schrader valve and listen. I heard a slight hiss. So there was nothing wrong with the valve.

Hook up the gauges and the vacuum pump, pull a vacuum again and she still holds a good vacuum. Try to fill again and still no luck.

So I thought "My problem is the A/C clutch is not turning on."

Check all A/C related fuses - All are OK. Re-seat all the A/C relays in the fuse box.

Then I thought "It has to be the A/C pressure switch not seeing pressure and therefore not allowing the pump to turn on".

So I setup for filling again and I thought maybe if I manually turn the A/C compressor (with a screw driver on the front of the A/C clutch) while filling that would get enough refrigerant circulating around so that the pressure switch would notice pressure and then allow the A/C clutch to turn on.

No dice.

So then I decided to fill a bit of refrigerant into the dryer high side fitting (since that is where the pressure switch is co-located).

No dice.

Give the pressure switch a few light taps with the end of a screwdriver.

No dice.

On a whim, I decide to goose the dryer hi side Schrader valve momentarily just to confirm that there was refrigerant getting in there.

As soon as I do this the pressure switch frees up and the A/C clutch activates. I can then fill the system normally.

My theory is that when you vacuum down the system the A/C pressure switch mechanism moves into an area that it does not normally excursion into. It then got stuck there. When I goosed the valve there was a pressure pulse that freed up the pressure switch.

You learn something new everyday.

Back to Scorpio bliss.

[Ed Lijewski]

I might have lightly tapped the Trinary switch itself to see if that released it.

On a complete a/c reseal of my '89 I also installed new Schrader valves (what the heck, why not...).

YMMV

[brokencase]

I did try to tap it (see above).

I think the next step would have been to jumper the switch to get the compressor going.

Should have asked Saul if he has a spare pressure switch. But if it ever comes to it, I think I could adapt a switch from some other vehicle.

Or perhaps something like this..
https://www.classicautoair.com/shop/ac- ... ry-switch/

[brokencase]

Now after some exploration I am wondering if it is indeed advisable to change the trinary switch to one more suitable to R134a.

Look here:
https://www.polarbearinc.com/SwitchesRe ... -Switches/

Compare these two switches"

SW 4001C
SKU: SW 4001C
Male R-12 trinary high & low pressure switch, fan on at 227 PSIG, off at 185 PSIG. Low opens at 28 PSIG closes at 29 PSIG. High opens at 384 PSIG closes at 284 PSIG


SW 4082C
SKU: SW 4082C
Male R134a trinary high & low pressure switch, fan on at 227 PSIG, off at 185 PSIG. Low opens at 28 PSIG closes at 29 PSIG. High opens at 454 PSIG closes at 369

[brokencase]

Someone in the IMON archives indicates that Red Dot 71R7550 trinary switch is a cross to the Scorpio and XR4ti.
here:
https://www.acparts.com/product/binary-and-trinary-3/

That description claims that it will work with both R12 and R134a
Pressures are:
low=22.5/40 high=325/230 fan=35-60/200-230 type of operation.

[Ed Lijewski]

20240526_121909_copy_1209x1612.jpg

20240526_121922_copy_1209x1612.jpg

I remove the clipped underhood seal sections during a/c use seasons to increase air flow through the condenser and radiator (and remount them during fall/winter).

(Don't give me any crap about photo size...these have been resized to ~450kbs.)

YMMV

[andyofcolumbusmerkur]

Photos look just fine to me, they are just a little smaller than the page is (Version 103.0.5060.132 (Official Build) (64-bit) using a $100 chromebook.

[Ed Lijewski]

TMK posters have no way to manage photo size. Appreciate info to the contrary. Photo files must be below a max size, but that's it.

YMMV

[brokencase]

Ah-hah! The big reveal here is Ed bought an AGM battery! When did Hell freeze over?

As I believe I related previously, my solution to greater airflow through the condenser/rad is to discard the stock condenser fan (which practically never turns on and draws too much current) and in it's place install an aftermarket fan that draws less amps (about 8-10 amps) and to alter the wiring so that the new condenser fan activates whenever the A/C clutch engages.

This arrangement works very well. I actually notice that the engine temp gauge reads a little lower then when A/C is on vs. when it is off.
It's not a big change, but it is noticeable.

However, one can do many things to try to improve the performance of the Scorpio's A/C system. But there is little to be done to overcome the core issues which are a lot of glass and a black leather interior. Even if you some how managed to install an F-150 A/C system into a Scorpio, it would still take a half hour to cool down the 120F leather seats.

[Ed Lijewski]

Damn: forgot to crop that pic .

Bought in December. Needed to change a battery in an XR, so moved the former working fine battery from Shadow to it and bought a Weize (pricing then was very good and no state tax as well).

Your fix is smart for operation in slooow traffic and idling. But it undeniably pushes air that already doesn't have straightforward underhood exits except below the chassis. Hot air wants to rise and move to dissipate heat

My mod increases the efficiency of the radiator fan pulling air through the condenser in all situations. It's effect on vent temps is very noticeable with the car underway even at modest speeds with the trans in 4th gear and engine RPMs only around ~1500.

All hail the Venturi Effect.

YMMV

[brokencase]

I am reluctant to cut up the hood weather seal.

I don't think there is any difficulty with the air exiting under the car. Especially if the car is moving at a decent speed.

However your fix may allow cooler operation of the airbox against the firewall.
Or perhaps not, because you are now directing heated air towards that region. One would have to take careful temperature measurements of that area and record them over time and under various conditions.

Vent temps are not the whole story. There is little difference between a 38 degree vent temp and a 42 degree vent temp.

From my perspective the only way to get any noticeable improvement is to increase the mass airflow through the vents. Even if this means that vent temps go up a bit. In other words you are better off with twice the airflow at 45 degrees than you are at a measly airflow at 38 degrees. You've got to cool down those black leather seats.

One item I have considered is 3d printing improved squirrel cage fans to install on the blower. Or perhaps some sort of higher RPM motor substitution.
These changes would make an already noisy system even noisier, but I think would be the only way to really make an improvement.

Another approach would be to open up or improve airflow at the recirculation inlet. I'm not even sure where this, but if you could open up it's size or put a rounded edge on it's perimeter this might help increase airflow. But if the real air flow restriction is at the vents (or eleswhere) then this may not help very much.

[Ed Lijewski]

33.3*. I could have 32*s as well but clicking the photo app in one hand is iffy.
.
.

20240529_090626_copy_1209x1612.jpg

20240529_090615_copy_1209x1612.jpg

YMMV

[brokencase]

That is all fine Ed, But try this experiment. Park the car in full sun on a 95F day for a couple hours. Windows shut. Let it get nice and toasty. Point your HF non contact temp sensor at the seats and confirm they are at ~120F.

Keeping the windows shut, start the car and turn on full A/C and tell me HOW LONG IT TAKES to get your 33F vent temp.

Better yet, FORGET THE VENT TEMPS. If you can stand the heat, just sitting there, tell me how long before you can say "It's now comfortably cool in here."

Your lucky if this can be accomplished in 20-25 minutes. And therein lies the problem. Most trips I take in my Scorpio these days are under 20 minutes.

Now, compare to my 2019 Ford Ranger, like my Scorpio it is white with a black interior (but not leather). Under the same conditions I get in the truck and I drive 1.5 miles with full A/C and it becomes actually TOO COLD, and the next thing I'm switching to AUTO and setting the temp to 70F.
The dash vents on the Ranger are double the size of those on the Scorpio. The air blasts out of them.

It's not all about the vent temps, it's the volume of air that is moving through the system.

I wonder if I pulled the vent directors out of the Scorpio's dash vents if that would increase the airflow. They are quite restrictive, and the turbulence they generate contributes to the hissing noise of the system. I would venture to say that about 1/4 to 1/3rd of the airflow is blocked by the director mechanisms.

If that makes a significant improvement, then I could 3d print some thin blade, low restriction vent directors. Up down adjustment only. Just have them at a fixed side to side angle that points to the the driver and passenger.

BTW, I looked at the EVTM manual and I could not find out where the recirculation inlet is, it's under the dash somewhere but I could not find it.

Is there a screen in front of it? What prevents debris being sucked into the evaporator when in RECIRC mode? I'd like to at least inspect mine to make sure there is no junk in there.

[Ed Lijewski]

Do your vents still have these?
.
.

Screenshot_20240530-191525_Gallery.jpg

YMMV

[brokencase]

My vent doors and motors are working fine. My whole A/C system is working as it should.

I just think the Scorpio's A/C system is a poor design and I am brainstorming ideas to make it better.

Back in the days of the IMON list I have described how I "fudged" the de-ice thermistor and was able to adjust vent temperatures to go below 32 degrees if I so desired. Naturally one does not want to go below 32F for fear of condensation freezing up the evaporator.

But over time I have come to realize that vent temperatures are not the real issue.

The real issue is that there is just not enough air blowing out of the vents to cool down the cabin effectively.