A/C Drier - does short drier change R134 charge?

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CruiseOrlando

CruiseOrlando

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I'm going to re-do my drier and expansion valve, flush the system, etc next week.

I got the 'short' receiver/drier (88471-34010) which will be replacing what I assume to be the original drier on the rig ('94).

Do I need to adjust the weight of 134 I dump into the system when I put it back in? I know the amount of oil I need to add (it's in the instructions that came with the drier), and IIRC the manual says 4.1 lbs of 134 (I have a scale and a big tank of it, so no problems in getting the right amount in)... but I don't know if that extra 3/4" is going to make a difference in the amount that I should put in? Or am I over thinking this too much and just put the 4.1 (or whatever the right amount is) in?
 
I'm not sure of the charge amount, but I think 4 lbs is way to much - you may want to check the manual again. The receiver/drier is designed to act as a reservoir of sorts and a small decrease in charge in theory should accompany a smaller volume, so you might want to try a few ounces less when you recharge it.
 
Yes, that 4.1 must have been for something else I was reading about :)

Refill is supposed to be 29.98 +/- 1.76oz.

So I'll start at the low end and work my way up :)
 
What is the approx difference in size btw the original drier and the new one? As mentioned, the "drier/receiver is a resevoir or tank, as the expansion valve will fluctuate flow depending on "heat" load and demand... A normal expansion valve will regulate refrigerant to maintain 5-20 degrees of superheat at the outlet of the evaporator, or inlet of the compressor. Superheat is the amount of heat absorbed above its saturation pressure/temperature (every pressure of a certain gas has a correlating temperature). So if you measure the pressure ( with your "low side" gauge at the compressor and find a "pressure temperature chart" for r134a, to find that pressures corr. Temperature, then measure the actual temp of the suction line at the compressor, that difference will tell you how much of a vapor the refrig is.... Aka,how protected your compressor is from chugging liquid and blowing seals... Low superheat= overcharged or other issues...high superheat could indicate low charge... Sorry for the refrig rant, but i would confidently say a reduction in drier/receiver size if not drastic, shouldnt warrant a charge adjustment.
 
Thanks for the insight... I haven't measured them personally, but I believe the difference is about 3/4". Not much.
 
From what I can find:

"Short" drier, p/n 88471-34010
Height: 7.50 inches

OEM drier, p/n 478-0503
Height :11.69 inches

So if I'm looking at the right parts, that's a full 4" difference. However, others on various threads say the difference is more like 3/4". I haven't gone out to compare the one on my truck now to the new one I have in the box.
 
Yes, moving the lines a bit is on my list. I'm pulling all the lines out to flush them, replace all the o-rings, etc. I figure it probably has never been done, and while I'm in there... oh yeah, I'm going to pull the the evaporator and give it a nice cleaning as well.

Once the project is done I'll report back how much R134 she took for reference since I have the scale and all.
 
Forgot that there is a sight glass in the system... As you charge, the sight glass (drivers inner fender, under hood) will be "flashing" aka bubbling... Charge until you have a "full" sight glass with no bubbles, with the ac cranked of course.
 
Okay, just finsihed up the job a short bit ago.

Here's a shot of the two driers, side by side.

IMG_1939.jpg


I also pulled the evaporator box and changed out the expansion valve. After flushing out the evaporator, I didn't see much gunk at all, so I didn't try and flush out all the individual lines in the system.

Then I cleaned out the evaporators' exterior, which was in surprisingly good shape (I had run some evaporator cleaner in there a few months ago, which may have cleaned out a good bit of it, but that's hard to say since it was one of those 'closed system' cleaners).

I also took some time to re-glue the foam stuff back into the inside of the box, as it was all pretty much coming apart... then I cut some new foam for the other connecting parts of the box, including where the lines come in thru the firewall.

Put everything back together, then purged with nitrogen and pulled a vacuum. After about 2 hours, it got down to right around 600 microns, so I left it there overnight. Came back this AM, and it was right were I'd left it. So onto filling.

She took right at 30oz. A/C is now cold as I've ever had it - got down to 36 at one point (in the center vent, fan on low, external air about 80 or so). I certainly can't complain! Before I did this, the best I could get out of the vent was about 55, and that was if I sprayed the front radiator with water and had a fan blowing on it.

Here's a shot of the guages with the rig at idle. I think this was taken with it around 28-29 oz.

IMG_1963.JPG


The airflow is improved a bit... but all in all, I'm very happy with the results.
 
I'll have to ask my father-in-law. He had some stuff left over from the last job he did. It was pretty nasty stuff... And it took forever to get it all out of the evaporator after the flush.
 
I've done a couple - my father-in-law is the experienced one I was learning from.

A lot of your ability to succeed comes in doing things the right way (replacing seals when you take things apart, paying attention to things like oil, and having the right equipment.

I'd be happy to answer whatever questions you have, tho. I was pretty happy this job went so well.
 
Kernal said:
What product did you use to flush the evaporator?
Click to expand...

The flush we used is made by Hecat and is called "Safe-Flush A/C". He's ordered it from ACKits out of Arizona. They have some interesting information on their website, and some useful parts for doing AC work. We get the 1/2 gallon containers as they're easier to work with when you have limited use (small jobs).

Here is the link for Hecat flush.

Since my system was pretty clean, we didn't go into the other flush for the entire system - but if we had, we would have used this from AutoZone.

There's also some stuff from NAPA, but it's expensive - like $150/gallon IIRC. It seems the Hecat and/or Flush and Clean do just as good of a job, however.

But just for comparing, here is a link to that.

As for HOW to flush it, we used a flush gun made by Mastercool. I think you can get it from NAPA, but ToolTopia has it for less.

I'd be willing to bet Harbor Freight has something similar as well, but I've never looked for it there.
 
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