AC Condenser Cooling Fan

[Ed Lijewski]

I set the EATC to Center Vents, all year round (Defrost if needed but back to Center Vents after).

XR and Scorpio systems appear equal in size (compressor, condenser, evaporator, condensor fan ('89s), receiver/dryer, expansion valve, blower box and blower motor...everything.

XR center vents however are mounted ~12" higher than the Scorpio's. That makes a tangible difference as the vents also allow movement of cooled air to be directed higher, with the effect on passengers felt literally from head to torso to foot. Scorpio center vents have comparably limited arcs and can't achieve that. Driving or riding in an XR the effect of a/c is felt earlier.

On the rear windows of each of my Merkurs I have a sunscreen installed to reduce solar effect on that section of the passenger compartment. I think it helps the a/c system to cool the compartment. Tinted windows certainly would also help (and look good).

I'm aware of some of those substitute's claims re compared to R12 and data they present show a de minimus improvement if at all and if they are to be believed.

[john keefe]

Same thing with my F-150, white on black. I prefer driving the Scorpio around for small errands, but I know if it's gonna' be hot in the car, the truck will cool far faster.

Seems like just about any car I get into these days has some pretty good air flow, esp. in comparison to the Scorpio. Lot of noise, not much action, which same could be said of... (insert your own comment here; I know you're thinking it)

So, nothing to improve upon the Scorpio AC, or nothing's worked thus far? Is there a rating to compare compressor's, maybe other than cfm? I'm thinking from recollection that the 5.0L had a substantially bigger compressor, but it was kaput so AC didn't make it into the 5.0XR.

[Ed Lijewski]

Do the Brokencase mod to have the a/c fan run whenever the compressor is activated. With R134a in your system that could made a marginal difference, maybe more, on initial a/c activation and on highways.

YMMV

[brokencase]

You have to realize the Scorpio's initial target market in the late 80's was Europe. Most people in Europe did not grow up with vehicle air conditioning.

Case in point... go to this Scorpio promotion video and scroll to 10:56
https://www.youtube.com/watch?v=omaiE1M8nzY

British Aristocrat proclaims..."I only discovered air conditioning about 2 or 3 years ago...and I thought oh! This will be nice when we head on down to the south of France".

The long and short of it is the Ford engineers could have blown a fan over an ice cube and these customers would have been amazed.

The bar was not set very high.

[brokencase]

Do the Brokencase mod to have the a/c fan run whenever the compressor is activated. With R134a in your system that could made a marginal difference, maybe more, on initial a/c activation and on highways.

YMMV

Ed, As I have described previously, it helps in the summer when you are stuck in traffic.

At my prior job I would have a 30-40 minute drive where I would hit traffic lights (and backups) for the first five miles of the commute.
Think about it...it would take me 30-40 minutes to drive 9 miles home. I could have bicycled that faster, and if the roads were not so dangerous I would have.

Alternatively, I could have taken the turnpike (and pay a toll) and I would have been up to highway speed very quickly and the mod would have been less useful.

[Ed Lijewski]

Yeah, reminds me of the roads around Carlisle in every direction, clogging up so easily, and traffic going almost nowhere for minutes and minutes and minutes. I couldn't live there or work there.

I don't encounter those conditions, regularly.

So bottom line, John's weak a/c output merits installing your mod now.

If I move to FL or AZ or TX I'd likely do it.

YMMV

[brokencase]

So what are the things one can do to help keep the Scorpio cool in the heat?

1) Park in the shade (and pop the sunroof) This makes the most improvement IMHO.
2) Use a windshield shade if you can't park in the shade.
3) Window Tint. I had dark tint on my old Scorpio but I got a warning from police in PA. On my current Scorpio I installed the newer light tint with IR blocking. Helps a little.
4) The condenser fan on when a/c clutch activates mod (along with swapping out to a modern electric cooling fan that draws less current)
5) There is another mod you can do to lower the evaporator temps by fooling the de-ice sensor. I pioneered this mod back on the old IMON list. Folks in the UK took it further...http://www.fordscorpio.co.uk/acmod.htm
I did this on my prior Scorpio and it helps a little, you can lower the temps coming out of the vents with this mod, but again, its the issue with lack of air flow through the vents that is the real problem.
6) We were reminiscing under the club tent at Carlisle and the subject of hatch back louvers came up. I think they would look cool on a Scorpio and they would help it stay cool also.
7) I'm wondering if you could do a comprehensive flow study of the duct work on the Scorpio. Treat it like a cylinder head porting problem. Open up the entry holes from the fan to the condenser area. Remove all sharp edges. Use JB weld to create rounded, bell shaped edges where needed. Stuff like that. It would be a lot of work but it might pay off. You might also reduce noise.
8 ) 3d print new "high flow" Squirrel Cage fans for the blower assembly. I'm liking that idea! This would take some experimentation and research. However there are several parametric fan models already available up on thingiverse.com...so modelling/printing the fans is not an issue. The issue is how do you change the fan's design to get more flow? Fewer but larger blades? Change the airfoil shape of the blades?

[brokencase]

Below is my original IMON post regarding the de-ice sensor mod. I think I might try this mod again on my current Scorpio.
I was pleasantly surprised to find that my old webpage http://web.starlinx.com/dhedin/ can still be accessed through https://web.archive.org/

Try this link...https://web.archive.org/web/20011112005 ... om/dhedin/
If you go to my "Scorpio inks page" you can access some other older Scorpio related webpages also archived.

Unfortunately. I never got around to posting this de-ice mod on that webpage.


"I think I might have found the ultimate cure for the Scorpio's
poor A/C performance. The following modification seems to do
the trick. However, I just did this today (8/1/99) and it has
not yet been "time tested" so proceed at your own risk.

In addition, this mod assumes that you have a perfectly
functioning A/C to begin with AND I recommended that you
have performed the "A/C electric fan on when A/C Clutch on"
modification that has been previously described in the archives.


THE THEORY:

The main controlling element of the Scorpio A/C is the de-ice
sensor located on the front passenger side of the evaporator
box. This sensor controls when the compressor is turned on
and off. It will turn on the A/C clutch when the vent temp
rises above 50 degrees and will turn it off when the vent
temperature falls to about 45 degrees. This data is based on
fellow list members Richard Johnson's informal A/C survey
as well as my own measurements after recently recharging with
R-12. Thanks Richard for your input.

Note that the above temperatures are measured at the VENT and
that the actual core temperature (where the sensor measures)
will usually be slightly lower. As the name implies the sensor
is there to prevent the evaporator from icing up.

In my opinion, this range is set a little on the high side on the Scorpio
What I wanted to see is a range more like 38-43 degrees.

The de-ice sensor is a black box with an attached sensor probe
that projects into the evaporator core. It's a little tricky to
remove. You will have to get a small 90 degree phillips
driver to get the bottom screw out. Once you have the little
box loose you then can carefully remove the probe from the core.

I was hoping that I would be able to open up the little black
box and find some factory calibration screws but unfortunately
the unit is potted shut.

It turns out that the probe is actually a negative temperature
coefficient thermistor. At about 80 degrees it measures about
10Kohms and at 32 degrees it measures about 35Kohms.

What we have to do is somehow fool the little black box into
thinking that the evaporator is warmer than it actually is by
lowering the effective resistance of the thermistor. We do this by
putting another resistor in PARALLEL with the thermistor.

For experimentation purpose I wired in a potentiometer in parallel
with the thermistor.


THE EXPERIMENT:

I made the wires long enough so that the potentiometer would reach
into the cabin. My initial calculation to shift the resistance by
about 10 percent implied that I needed about 1 megohm in parallel.
I ended up using a 500kohm potentiometer with a 470kohm resistor.
in series.

Driving around (in 90 degree weather) with the maximum resistance
setting, the vent temperature cycled around 39-40 degrees.
I lowered the resistance and I was able to achieve 36 degrees.
I did not want to go any lower although I could have.
Once you get below about 40 degrees the compressor rarely turns off.

I added a little more resistance (330K ohms) for a total of about
a 1.4 megohms and I was able to get the temps to cycle between
40-43 degrees which I felt little safer with.

The results were excellent, a 5 degree drop in vent temperature
doesn't sound like much, but it really made a noticeable difference
in the perceived comfort.

THE CONSEQUENCES:

You have to exercise a little caution here. This is definitely not
a case where "more is better". Keep in mind that as evaporator
temps go down, condenser temps go up and compressor gets no rest!


THE MODIFICATION

After my little experiment I began to think a little about it and
decided that the safest way to do this would be to have a fixed
resistance wired to a switch mounted on the dash that would "cut in"
the parallel resistor. Sort of an "aftercooler" switch

Thus on very hot days (which we have been having a lot of lately
here in the NE) I could turn on the extra cooling. Once the cabin
temp comes down I could then turn it off and let it cycle at the
factory setting. I will also leave it in the off position for the
rest of the year when it is not so hot out.

Note that this way I have an "out" if things get out of control,
Like if the engine overheats, or the compressor start making noises,
or the evaporator starts icing up etc... Which I hope doesn't happen.

There may be a better way to do this. Perhaps an aftermarket "universal"
adjustable de-ice sensor exist. If you know of one, post it on the list.


MORE DETAILS:

I will post this modification on my web page (with pictures) so please
do not email me off list until I get it up.

http://web.starlinx.com/dhedin/

Click to the Scorpio pages, then projects

If I make any ongoing changes/correction I will post them on the list.
Thats all for now.

Dean
One cool '88 Scorpio "

[Ed Lijewski]

Thanks Dean for all the info above. I have several observations to add to the mix. I'll start with this one and add others to it later.

The deicing switch prong installation from the factory included an alignment piece ostensibly to keep it from direct or really close contact to an evaporator coil. That piece falls off when the switch is pulled out with the two halves of the blower box clips holding them together. See the white cone like unit in photo below.

On reinserting the switch in the blower/evaporator boxes I place a section of plastic drinking straw on the thermistor shaft as shown in photo below (the section could be a bit smaller in length).

The purpose is to assure the sensor doesn't touch or reside too close to a coil so.it doesn't depower the compressor prematurely.

YMMV

[Ed Lijewski]

Regarding blower air output from the vents, on my '88 some years ago on one occasion when I had the dash cover off I noticed that the air tube to the passenger side vent didn't have a tight connection. I then checked at the center and other side vent and noticed those connections weren't as tight as optimal either. So I wrapped those connections with a thread of duct tape (side connections were easy to do, not so the center connection). Any difference in blower air output would be marginal but positive.

I haven't looked at the other ends of those tubes, at the blower box but that might be worthwhile to do as well.

YMMV

[brokencase]

I'm aware of some of those substitute's claims re compared to R12 and data they present show a de minimus improvement if at all and if they are to be believed.

Well you're wrong. The hydrocarbon refrigerants work as well or better than R12, R134 etc. As I indicated Europe is looking at a total phase out of fluoro-carbons by 2022. Although I am not certain if this phase out will apply to automobiles.

Just do a little research...
https://truerefrigeration.eu/2019/05/wh ... perations/

"Its capacity to absorb heat is nearly 90% higher than R134 or R404 which results in quicker temperature recovery and lower energy consumption".

And this document reports a 10% improvement of HC drop in replacement over R12
https://www.es-refrigerants.com/resourc ... IONERS.pdf

I don't know why we ever went down the road to flouro-carbons in the first place. Something DOW chemical told us we needed I guess.
Just like we needed tetra-ethyl lead in our gasoline.

[Ed Lijewski]

The 10% referred to "cooling capacity" which wasn't explained further nor were any pressure/temperature charts presented showing its performance, and compared to R12 and other drop-in refrigerants. So it's rash to simply infer that that hydrocarbon blend produces 10% better cooling under all temperature conditions and pressures.

No hydrocarbon refrigerants are approved for MVAC use (retrofit) by EPA under its SNAP program. I have an EPA certificate (passed its test).

https://www.epa.gov/mvac/new-climate-fr ... frigerants

Some MCA peeps have retrofitted with Envirosafe (hydrocarbon) which seems to have lost its market luster for some reason; at least one peep here used Duracool (hydrocarbon), and I bought some Duracool and used it very very briefly but decided to go back to R12 given it is propane.

Your Europhilia re only they are pursuing development of better MVAC refrigerants should be embarrassing but alas isn't.

Larry Carly presents a concise overview of MVAC refrigerants evolution:

https://aa1car.com/library/newac2k.htm

(R12 was developed by Dupont, not Dow.)

YMMV

[Ed Lijewski]

Yesterday on my '89 I noticed that almost no air came out of the passenger side center vent where before some did (although not as much as from the driver's side center vent). Examining it with the wood veneer strip off I saw that the motor driven door was in closed position, even though I always set and leave the EATC in just Center vents On position. The other center vent doors were fully open. Whatever the reason for this anomaly, I note it here as I've also pointed out earlier that one or all of the center doors can either not open fully (they become warped over time) or experience some other gremlin such as above, which diminishes air flow.

I turned the key off and on and set the EATC to floor mode and the passenger side vent door opened fully. I won't look into it further as there are other tasks with higher priority and overall the cooling provided is fine.

YMMV

[john keefe]

Ed, any link or ref to what it takes to convert an R134 system? Or has this been discussed ad nauseam before? Based on some of the commentary in the Carly article, I assume there have to be better seals, et al with any "upgrade," but are swaps done without extensive parts replacement?

[Ed Lijewski]

John:

I think it's best to let Dean describe what he did in his conversion to R134a (and maybe also didn't do, e.g. replace expansion valve, replace hoses with barrier hose, change condensor?).

YMMV