Initial readings: 33/250 at 95 degrees - next steps?

[msrichmond]

I overcame a defective (but new) Four Seasons 59199 gauge set, a useless self-sealing can adapter (with a T handle) and a not-too-useful self-sealing can adapter with a plastic knob, finally using a Harbor Freight gauge set and a Robinair can tap.

I pulled a vacuum for 45 minutes, got about 6 oz of gas in the blue side and the compressor kicked in when I started the car. Yay!!

I nursed about 16 ounces of refrigerant in before I called it a day.

My configuration is on the maybe-too-small side. The car is a 1974 Fiat 124 sedan with a 1756cc twincam. I picked a genuine Sanden compressor, but it is the small 5 cylinder unit. The evaporator is a well-known USA vendor in Texas that boasts of having big innards for their evaporator. I picked it in part because it has LH fittings and it matches the style of the car. The condenser is the real compromise - only 10 x 18. I didn't want to do this project only to find that I couldn't make anything work so I picked that size because it fits without cutting anything, not even holes for the hoses. If I get close to a working system but need more capacity, I would consider some surgery to allow for something more normal size.

It seems to me that this small condenser will also mean I need less R134a.

I have two electric fans that come on at the same time one 10" and one 5". I should add that my primary need is for AC at highway speeds, at least for this summer.

I got maybe 16 oz max in today. I don't think the trinary switch ever kicked the fans on; it was the radiator temp switch that did. I can check this in the next session.

Here is what I recorded- 95 degrees ambient, 22% relative humidity outside but I was in the garage, so maybe a little more humid. Low side at 33PSI, high side at 250PSI. At times the high side needle vibrated +/- 10PSI.

I have a digital meat thermometer, it measured 55 degrees coming out of the vent.

Advice for next steps?

[Tim]

I am not going to address much more than a 10x14 cond. Something that small, no matter what design, is not going to remove that heat load very well. I am sure the pressures will drop if the cond is misted with water.

[tbirdtbird]

Agree. You always want to fit the largest condenser .
4squeezins products seem to always be a let down.
Hard to believe a Horrible Fright product worked better.

Is there a lot of humidity in your area? That will make your AC struggle. The air temp cannot be reduced until the humidity is reduced. Humidity is termed ‘latent heat’. You mentioned you thought it was low, wonder what the weather channel says. I always thought it was humid there

Can you install an insulating blanket on your firewall to reduce engine heat transfer. This is what we do when we install AC in a model A Ford (1928-1931). (this is a car that has absolutely no room for AC. We actually use a remote condenser behind the rear axle.)
Since it is inside the car it is not visible.

[msrichmond]

Agree. You always want to fit the largest condenser .
4squeezins products seem to always be a let down.
Hard to believe a Horrible Fright product worked better.

Is there a lot of humidity in your area? That will make your AC struggle. The air temp cannot be reduced until the humidity is reduced. Humidity is termed ‘latent heat’. You mentioned you thought it was low, wonder what the weather channel says. I always thought it was humid there

Can you install an insulating blanket on your firewall to reduce engine heat transfer. This is what we do when we install AC in a model A Ford (1928-1931). (this is a car that has absolutely no room for AC. We actually use a remote condenser behind the rear axle.)
Since it is inside the car it is not visible.

It is not humid in Oregon in the summer. High pressure sits over the east side of the Cascades, and when the ocean breezes flag, we get hot dry east winds. When the humidity on a summer day hits 60% with a high of 75, the natives moan "What's up? This ain't Michigan, is it?"

[msrichmond]

I am not going to address much more than a 10x14 cond. Something that small, no matter what design, is not going to remove that heat load very well. I am sure the pressures will drop if the cond is misted with water.

Sorry... I mistyped. It is 10 x 18. Also, I used heat transfer black paint.

[tbirdtbird]

I think you said you had 2 pusher electric fans on there. I have my fans come on whenever the comp is on. I have been criticized for this but even if you use a sensor to turn them on they will surely be on within 15 minutes, like, so what.

If they are pusher fans, they don’t do the job as well as fans mounted on the inside of the radiator…better to suck the air thru.
Also how far is the condenser from the rad? Should not be more than 1/2”, and using blocking material (can be anything) seal up around the edges on the condenser else the air will take the easiest path and go AROUND the condenser. Lazy air.

[msrichmond]

I think you said you had 2 pusher electric fans on there. I have my fans come on whenever the comp is on. I have been criticized for this but even if you use a sensor to turn them on they will surely be on within 15 minutes, like, so what.

If they are pusher fans, they don’t do the job as well as fans mounted on the inside of the radiator…better to suck the air thru.
Also how far is the condenser from the rad? Should not be more than 1/2”, and using blocking material (can be anything) seal up around the edges on the condenser else the air will take the easiest path and go AROUND the condenser. Lazy air.

The fans are behind the radiator and pull the air through. The condenser is no more that ½" but I could seal the edge. The reason I am using the trinary switch to kick the fans on (or the radiator temp) is because I expect a lot of my AC use to be on the highway.

[Carguychris85]

Not intending to degrade the project in any way, however I do not understand why more manufacturers are not building the microtube parallel flow style subcooling condensers with a built in receiver/dryer liquid/seperator in them. I tried to find one with suitable dimensions for my 1987 G20 van project recently. That style condenser is as efficient as they can get. They make a condenser slightly larger with that feature that would be a great help, IMO. The smaller the condenser the more that feature helps. The condenser I mention uses 3-4 passes for condensing the gas then the cooled refrigerant goes into a liquid/vapor seperator that doubles as a drier, then it makes the final pass as a liquid to further subcool the liquid. It is a fantastic design and has been OE on most Asian Imports for 20 years. I honestly do not understand why more universal fit versions are not a thing. Literally every condenser should be built with that design, they are more efficient in every way.

It would be fantastic if somone started supplying GIC 11 mm subcool condensers for universal applications. In applications needing a compact condenser for space reasons, they could use the appropriate sized condenser without sacrificing ac performance compared to old designs. You also would not need a remote drier or the added connections to leak. Trucks, SUVs and Vans would also benifit from reduced head pressure and additional cooling capacity in high heat and humidity especially at idle in traffic. I have a 2011 Pathfinder and 2019 Titan with this style condenser and both cool exceptionally well. Build one in a 31" by 15" core with R12 threads and I would buy one tomorrow same goes for a drop-in replacement for my 97 Express van.

https://www.denso-am.eu/news/deneur18_0 ... condensers

Denso claims they are 45% more efficient than a standard parallel flow, that is impossible to ignore and a huge jump in condenser efficiency. That 2019 Titan has something like a 30" x 25" subcool condenser, EV clutch and huge clutch fan. Using the factory R1234YF it will hold mid 30s at the center vent at idle with the blower at high speed on a 115F Texas summer day.