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A/C Replace

89er on Wed February 27, 2008 9:41 PM User is offline

Year: 1989
Make: Ford
Model: F 250
Engine Size: 7.5 L
Refrigerant Type: R 134a
Ambient Temp: 40 F
Pressure Low: none yet
Pressure High: none yet
Country of Origin: United States

Hello AC Guru's.

This is my first AC rebuild and I have a few questions. Hats off to ACKITS for a great site.

I've recently replaced my entire system with parts from but haven't charged it yet. Would it hurt to just vacuum the system, leave the compressor unplugged and wait for warmer ambient temps to charge? I've heard you need atleast 70 degrees F to get a good charge which is probably a few months away here it Utah.

My new Visteon compressor said it was shipped with 7 ounces of PAG 46. Would I need to add oil anywhere else with a new system?

Also I've heard you need to adjust the low pressure cycling switch using the set screw if converting to R134a. What's the best way to accomplish this?

Thanks in advance

89er on Fri February 29, 2008 12:14 AM User is offline

Thanks for the advice. I will definitely drain the oil out and just refill with fresh PAG 46 ensuring the correct amount and type and I guess I won't worry about adding oil anywhere else since the system is brand new. And I'll evacuate and charge the system over the weekend. I think it's supposed to be a high of 50 degrees around here this weekend. definitely won't need the A/C for a few months but hopefully it'll be in good working condition come June when it heats up around here. I guess I'll just play with the pressure switch and hopefully I'll get it right unless anyone has some advice that might save me some headache.

One more question... My new parts came with the original R12 fittings so I went to the local parts store and bought the R134a fittings that just screw on top of the R12 fittings. Do they screw on with or without the original R12 valve core's removed? I wasn't sure if it would make a difference. Anyone have experience with these?


Chick on Fri February 29, 2008 5:20 AM User is offlineView users profile

Opps, Cussboy, accidently deleted your post while trying to delete and "empty" post...Sorry about that....Please repost it..I'll wait til I have my second cup of coffee before cleaning up posts.....

I copy pasted your answer below but lost the avitor.....

Email: Chick


Freedoms just another word for nothing left to lose

Edited: Fri February 29, 2008 at 5:22 AM by Chick

Chick on Fri February 29, 2008 5:21 AM User is offlineView users profile


Senior Member

Posts: 161
Joined: Apr 2002
Thu February 28, 2008 6:26 AM

Personally, I would evacuate and charge now. Positive pressure of refrigerant will keep mositure from getting in. There is no "perfect seal". As to the oil level: personally, I would always drain out the oil (if any) in a new compressor, measure it to confirm the correct amount, then put it back in. In my case, since I have access, I would also confirm (using infrared spectroscopy) whether the oil was one for R134a or if it was R-12 mineral oil-type. A few years ago within a few months I installed two different Air Pro compressors (from this source) for 1988 and 1990 vehicles of same manufacturer; for the 1988 the oil inside was an ester-type oil, so that was flushed several times with mineral oil as that truck was staying R-12. For the 1990 car, the compressor already contained mineral oil, which was good, as it was also staying R-12. So I check.

Email: Chick


Freedoms just another word for nothing left to lose

Edited: Fri February 29, 2008 at 5:23 AM by Chick

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