Revisiting the A/C System

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Apr 23, 2019 | 12:04 PM

Da_Lariat_Chariot

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Revisiting the A/C System

Awhile back I posted my A/C conversion thread, it's time to do some adjustments. Just rented some pressure gauges and I'm getting 135 high side, 30 low side at idle, when holding RPMS above 1500 the high side goes to 160, low side down to 20 ish and the compressor cycles. Does not switch on/off at idle, it stays running. I used a blue orifice tube when I had it open last time, seems like a red tube would bump the pressure on the high side a little more, which would be a good thing I think? I'm 99% sure the compressor is ok because the difference between the two readings is still pretty large, even at idle. Thoughts about red/blue tube?

Apr 23, 2019 | 01:11 PM

Hit Man X

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From: North Texas

Pressures are dependent on temperature, what was the ambient when you took these readings? Always take high idle readings. You sound low on refrigerant if it was a modest day, say around 80F. If you have to recover then recharge, I believe a 1994+ parallel flow condenser will drop in and they are about $70 new. Looks same from my '96 to my '88 width wise...just a bit longer, it will drop high side head pressures quite a bit due to superior cooling.

I too am curious about the orifice tube differences.

Apr 23, 2019 | 02:22 PM

timbersteel

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From my limited AC retrofit knowledge, "Blue" orifice tube for R12 and "Red" for 134a.

Apr 23, 2019 | 03:35 PM

tjc transport

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i agree that it sounds like you are a bit low on refrigerant. i use this chart to determine correct charge:

Apr 26, 2019 | 12:30 PM

Da_Lariat_Chariot

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Laughing Gas

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Quote:

Originally Posted by tjc transport

i agree that it sounds like you are a bit low on refrigerant. i use this chart to determine correct charge:

I will check how much is in ... Put 40 ounces into it last time around

Apr 26, 2019 | 12:59 PM

ford390gashog

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From: Brentwood,CA

Answer these questions and I can help

1. What was the oil charge of the system

2. Was the system pulled down under vacuum?

3. Was the refrigerant pure or was it oil/dye charged?

4. Was the refrigerant charge weighed in?

Apr 26, 2019 | 01:07 PM

Hit Man X

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40oz of what?

Apr 26, 2019 | 02:18 PM

Da_Lariat_Chariot

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Laughing Gas

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Quote:

Originally Posted by My4Fordtrucks

I assumed 40 ounces of R-134a.

Quote:

Originally Posted by ford390gashog

Cannot remember how much oil, im pretty sure I looked it up and used what was called for.

System vacuum checked at 30 in hg and it sat for 2+ hours with no change

Pure R134a from a tank, 40 oz

Apr 26, 2019 | 08:40 PM

#10

ford390gashog

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From: Brentwood,CA

Was that 40oz weighed in? It should be near a correct charge, I think your orifice tube is causing the low side draw down at high rpm. My suggestion is the red or a variable tube.

Apr 27, 2019 | 01:13 AM

#11

Da_Lariat_Chariot

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Laughing Gas

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Quote:

Originally Posted by ford390gashog

Was that 40oz weighed in? It should be near a correct charge, I think your orifice tube is causing the low side draw down at high rpm. My suggestion is the red or a variable tube.

It was dispensed using a Robin Air machine, it's accurate. Red tube will get installed when I have some time.

Apr 27, 2019 | 06:38 AM

#12

My4Fordtrucks

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Quote:

Originally Posted by ford390gashog

My suggestion is the red or a variable tube.

I only changed the accumulator, o-rings and installed a variable orifice tube when I converted my ‘89. It blows cold enough that I need to cut back the temperature.