1972 F-250 R12 system refurb

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rattle_snake
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Joined: Tue May 25, 2021 11:22 am

Re: 1972 F-250 R12 system refurb

Post by rattle_snake »

Thanks again Tim for your help.

Yes the system has a cable controlled temp switch (aka thermostat) that should cycle comp off when it gets below temp setpoint. I tested at all positions, perhaps cable shifted or device is broken. I could hear it open/close before install, so appeared to work. Maybe probe needs to be secured better in evap. Not sure where it should go, was shoved into evap fins so I put it back how I found it. It is the only electrical component I did not disassemble and clean/repair.
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Broken down and got a new vac pump to replace my old relic that gets seized up after awhile. evac'd immediately after pump oil fill and drier connection. 40 min.
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system was cooling Ok after just two 12 oz cans. Figured I stop at 3 and test drive instead of overfill (more is better, haha)
I tested off idle, ~1500 rpm and pressures were about the same as idle. I expected raise but settled out close to idle readings.
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tbirdtbird
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Re: 1972 F-250 R12 system refurb

Post by tbirdtbird »

In some cases the probe has to be in a certain location to work properly, but I do not know how to determine that. The original location may not be ideal

You are showing an auxiliary test fan in use. I assume there is no electric fan on the truck, just the mechanical. Is it shrouded?
Wonder how far the condenser is from the radiator. Was it moved at all? Needs to be pretty close else cooling air will just go around condenser. For our custom work we usually mount about 3/8" away, no more
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JohnHere
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Location: South Carolina Upstate - USA

Re: 1972 F-250 R12 system refurb

Post by JohnHere »

Looking at your photos, it appears that the truck has clear glass. In your area of the country, it would help lower the interior temperature by a few degrees, and ease the load on the A/C a bit, if you had the windows tinted.
rattle_snake
Posts: 11
Joined: Tue May 25, 2021 11:22 am

Re: 1972 F-250 R12 system refurb

Post by rattle_snake »

tbirdtbird wrote: Wed Jun 02, 2021 6:53 am In some cases the probe has to be in a certain location to work properly, but I do not know how to determine that. The original location may not be ideal

You are showing an auxiliary test fan in use. I assume there is no electric fan on the truck, just the mechanical. Is it shrouded?
Wonder how far the condenser is from the radiator. Was it moved at all? Needs to be pretty close else cooling air will just go around condenser. For our custom work we usually mount about 3/8" away, no more
No e-fans on this truck, not a good fit for my application, not enough airflow. I installed a 20" mechanical fan and new clutch assembly from 90s F350. New trucks still use mechanical fans.
the aux fan doesn't move much air. With previous engine/fan/lack of shroud the high side would go really high due to poor airflow.
I built a custom shroud out of sheet metal. Condenser, trans cooler and radiator are all very close, 1/4" to one another. Had to cut up the grill support to fit all of them. Also had to move motor back and down to move fan forward to clear compressor. A lot of work in packaging. some pics;
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Last edited by rattle_snake on Wed Jun 02, 2021 11:26 am, edited 1 time in total.
rattle_snake
Posts: 11
Joined: Tue May 25, 2021 11:22 am

Re: 1972 F-250 R12 system refurb

Post by rattle_snake »

JohnHere wrote: Wed Jun 02, 2021 7:39 am Looking at your photos, it appears that the truck has clear glass. In your area of the country, it would help lower the interior temperature by a few degrees, and ease the load on the A/C a bit, if you had the windows tinted.
Yes tint is on my list today. Classic pickups look good either way. But last trip sealed the deal, baking me through rear window.

I also plan to add killmat to the roof, and a layer or 2 of bubble insulation under headliner.

I have a custom fit windshield shade that helps too.
tbirdtbird
Posts: 110
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Re: 1972 F-250 R12 system refurb

Post by tbirdtbird »

Nice job on the shroud, they help a lot.
Please be reminded that the racing crowd determined years ago that the max air draw occurred when the rear of the fan blades stuck out of the shroud (behind it) 1/2". That dimension makes a huge difference
rattle_snake
Posts: 11
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Re: 1972 F-250 R12 system refurb

Post by rattle_snake »

Tbird, Agreed on shroud spacing, however I had to work within my packaging constraints. Had to move entire drivetrain (again) just to get fan to fit with a/c pump at all. Lots of work as you would imagine. Supposedly can cause cavitation which lowers efficiency. Pressure pinch point should be on blade tip. Exhaust fans are this way too.

My 2014 f250 has fan all the way in shroud though. probably a safety thing.
tbirdtbird
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Re: 1972 F-250 R12 system refurb

Post by tbirdtbird »

"The fan ideally should fit one half of the pitch depth of the blade into the shroud opening. If it is too far rearward out of the shroud air will be pulled from around the blade tips. Being too deep into the shroud can cause turbulence affecting airflow and cooling ability."

Source
http://www.lockhartmachine.ca/fan_blade_clearance.html
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