Replaced AC Compressor, now line freezing - Diesel Forum - TheDieselStop.com
7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

 
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post #1 of 8 (permalink) Old 08-03-2018, 12:55 PM Thread Starter
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Replaced AC Compressor, now line freezing

I recently changed the AC compressor and accumulator, and the system seemed to work fine, but once I started driving some distance, the fan speed would change from "high" to nothing coming out of the vents (they feel cold, but no air flow). If you put the system on "vent" instead of AC for a while, it thaws it out and fan speed works fine again. When I look under the hood, instead of the accumulator being cold and having condensation on it, it's hot, very hot, and the line underneath it is frozen/ice cold/condensated.

Not sure what the issue is here, but it's something I need to address. Don't want to ruin my new compressor. Plus would be nice to have AC for more than about 40mins.

Why is the accumulator hot? Why does the fan blower stop working? What's going on here?

'91 F-250 7.3idi XLT Lariat Supercab
Non-Turbo, Bone Stock
E4OD 4x2 4.10 non-posi
6 full digit mechanical odometer (7 slots)
155,000 miles (250,000km)
still Minty Fresh-ish

Sold my old 90 reg cab @340,000 miles (550,000km)
Still running I'm sure...
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post #2 of 8 (permalink) Old 08-03-2018, 05:51 PM
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It sounds like the evaporator is stopped up exterally. The cooling fins need a good cleaning. Freezing up like that is because the refrigerant can't cool off after it is compressed, so it circulates till it gets hotter and hotter. The fan stops because the ice build up stops it. The ice build up happens because there isn't enough air flowing across the evaporator.

Edit: This is all assuming you have the charge correct

1993 F-350 crew cab non-turbo 5 speed transmission
35 years a mechanic on large stationary engines natural gas and diesel fired, and other industrial equipment.

Last edited by oldrebuiltdodge; 08-03-2018 at 05:54 PM.
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post #3 of 8 (permalink) Old 08-03-2018, 06:11 PM
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Refrigerant work is not for shade-trees. Take it to a pro before you cost yourself more money.


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post #4 of 8 (permalink) Old 08-03-2018, 06:46 PM Thread Starter
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it's likely the charge is wrong. It's been adapted at some point in the past to 134a. All I did was charge it with oil and then refrigerant from a can. Not very accurate. I guess I'll take it somewhere to have it evacuated and refilled. Doesn't really seem all that complicated, but it's obviously not filled properly right now.

'91 F-250 7.3idi XLT Lariat Supercab
Non-Turbo, Bone Stock
E4OD 4x2 4.10 non-posi
6 full digit mechanical odometer (7 slots)
155,000 miles (250,000km)
still Minty Fresh-ish

Sold my old 90 reg cab @340,000 miles (550,000km)
Still running I'm sure...
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post #5 of 8 (permalink) Old 08-04-2018, 01:19 AM
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Quote:
Originally Posted by Steve83 View Post
Refrigerant work is not for shade-trees. Take it to a pro before you cost yourself more money.
I used to think the same. But it's not really rocket science. With enough research, AC work is not that complicated.


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post #6 of 8 (permalink) Old 08-05-2018, 11:16 AM
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I used to think the same. But it's not really rocket science. With enough research, AC work is not that complicated.
Just expasnion and compression of a gas, and the method of controlling it. It works the same way in any a/c unit, it's all just controlled, and used differetly. Even compressed air will react the way refrigernant will, but not to that extent, unless it is compressed enough to turn to a liquid. The various refrigerants are used because of their low liquify pressures, and they aren't flamable.

1993 F-350 crew cab non-turbo 5 speed transmission
35 years a mechanic on large stationary engines natural gas and diesel fired, and other industrial equipment.
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post #7 of 8 (permalink) Old 11-10-2018, 04:22 PM
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These are what is called a critical charge system, please note the word critical there!

Step 1 - Clean coils, ensure condenser is clean, and evaporator is clean.

Step 2 - recover all gas in system, then pull a 1000 to 500 micron vacuum for an hour

Step 3 - it will take exactly 2 cans of redteck 12a (32 ounces equivalent) if set up for the original R12

Step 4 - run unit for a while and observe suction line pressure and monitor clutch it should disengage at apxly 32f equivalent pressure, if it does not then the low side switch will need to be replaced / adjusted

this is off memory while tired, but this will get you in the general area.

New truck: 1988 F-350 1 ton dualy 2*4, 7.3L IDI Naturally Aspirated, Dual tanks with Camper package.
Mods: Enhanced gauge cluster; Transmission temp, rear diff temp, coolant system pressure, Vacuum pressure, Fuel pressure, Crappy tire Air horn Kit, Raycor pre filter/water sep. All LED Dash lighting, Parker LFS tranny filter, super duty tranny cooler, gerret turbo, waste gated (pending).
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post #8 of 8 (permalink) Old 11-10-2018, 04:28 PM
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Quote:
Originally Posted by oldrebuiltdodge View Post
Just expansion and compression of a gas, and the method of controlling it. It works the same way in any a/c unit, it's all just controlled, and used differently. Even compressed air will react the way refrigerant will, but not to that extent, unless it is compressed enough to turn to a liquid. The various refrigerants are used because of their low liquify pressures, and they aren't flammable.

Actually air is used in some cases as a refrigerant as is CO2, known as supercritical refrigerant cycle, then we have R290 (propane) that beats the crap out of R22 in over all cycle efficiency, R-600a (Iso butane) used in allot of fridges now days. Older but still the best is R-717 (Ammonia) toxic and flammable but the best for mass cooling.


Water is used as a refrigerant too for massive cooling systems above 6c in absorption mode or centrifugal systems


https://www.chillercity.com/Refrigerant_Data.php


Redtech and such over the counter refrigerants are Alkane based (Hydrocarbon gasses)

New truck: 1988 F-350 1 ton dualy 2*4, 7.3L IDI Naturally Aspirated, Dual tanks with Camper package.
Mods: Enhanced gauge cluster; Transmission temp, rear diff temp, coolant system pressure, Vacuum pressure, Fuel pressure, Crappy tire Air horn Kit, Raycor pre filter/water sep. All LED Dash lighting, Parker LFS tranny filter, super duty tranny cooler, gerret turbo, waste gated (pending).
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