AC help

[Lars]

Has anyone else heard that R134 is heading to the same grave site as R12?


Seems like I read this recently but don't remember where. One thing is certain, it has doubled in price in the past year.

 

[landtank]

My understanding is that the pat. rights were do to expire on R12 so Dupont had lobbyist get behind their new 134 which was better for the enviroment. Now when the patent rights expire on that one I'm sure we will see yet another new and better patented replacement from Dupont.

 

[Rich]

The price on R134 has gone up becuase the supplies are a bit short to meet demand. I wouldn't be surprised if at some point R134 gets replaced as it is not as effective as R12. That in itself motivates the industry to come up with something better.

 

[re_guderian]

ANSWER:

The Pressure Temperature Relationship varies with ambient temperature.

Here is a guide line for R-134a (R-12 is slightly different).

Low Side..........High Side..........Ambient Temp. (F.)

16-29..............115-200..............70-80 deg.

19-39..............140-235..............80-90 deg.

25-43..............165-270..............90-100 deg.

37-51..............210-310..............100-110 deg.

As you can see ..."figures" rise as the ambient temp. rises.

Flintknapper,

I appreciate your table here. I wonder how you got your numbers on the high side? They seem to be a little higher than the FSM suggested 2.2-2.4x ambient. I'll have to say though, I agree with you and let me say why. I've been fighting intermittent "warmer than desired AC", and even had it cut out after a freeway run at 115+ degrees. I started with new blue-base fan clutch, and today at 105-ish, no issues after long freeway runs. I picked up a set of R-134 manifold gages and spend about an hour searching here. What I found is this.

1- a LOT of people seem to have issues with warm AC. They seem to fall into two camps, those that just "dump some more 134 in" and seem to be happy, and those that follow the FSM to the "t" for both H and L pressure readings (with no results posted as to achieved vent temps).

2- general consensus that AC temps in hot ambient weather will rise at stops and low speed/idle. I found this on my first wheeling trip, quote from "it's too hot..."

3- No concensus (maybe there is/could be a poll on this) what a "decent" vent temp would be for a healthy AC in 100 deg low humidity day.

I figured I'd be conservative, and follow the FSM. Started out with best case vent temp around 48, worst case around 58 at stops. That sucks when it's 110 out. My '00 Avalon will feeze me out all day long. I know it's not necessarily the same, with an extra electric fan on the Avy, and smaller cabin area, etc., but shows me I'm far from "optimal". Anyway, on the 80, my low pressure was around 40 psi, high at 300 psi. My garage was ~100 degrees . So according to the FSM high side spec, I'm over-charged since max should be 2.4*100=240psi. So I adjust accordingly so that my high is at 250, and my low is about 24. Great, I think. Now I'm in compliance with factory spec. Sight glass shows milky white. No individually discernable bubbles to the "sight-glass-challenged" like me. So what do I get for my efforts? At 1500 RPM a vent temp of 59 degrees.

Tomorrow I'm gonna "Simple Green" my condensor and radiator, and then charge high side up to 310-ish per Flintknapper's chart, and check drive belt tension. In the FSM, "Volume of Refrigerant" is #1 on the to-do list. #2 is use manifold gage.
I don't have a belt tensioner, but if the high side is 300, I don't see how there could be a belt-slipping issue, especially at idle.

My favorite quotes from the FSM...

pg AC-22. "Symptom - No bubbles present in sight glass. Amount of Refrigerant = None, suffcient, or too much" gee, that really helped

"*Bubbles in sight glass with ambient temperatures higher than usual can be considered normal if cooling is sufficient"


And on a totally different tangent. Many of you may know I just purchased my truck from a fellow Mudder. I just want everyone to know that it was a very pleasant deal, and that by posting my "issues" or "problems" or whatever here that I am in no way trying to disparage the most-esteemed PO, or indicated that the truck was not as represented, or well maintained, etc. etc. Hey, they're 10 year old trucks that get beat up pretty hard. So, peace...

 

[Rich]

...
pg AC-22. "Symptom - No bubbles present in sight glass. Amount of Refrigerant = None, suffcient, or too much" gee, that really helped...

..."*Bubbles in sight glass with ambient temperatures higher than usual can be considered normal if cooling is sufficient" ...

In R134 systems the site glass is not an accurate means for determining that the refrigerant is correctly charged. That is what the manual is telling you. This is common knowledge. This is also why many manufacturers have eliminated site glasses from R134 systems.

 

[e9999]

In R134 systems the site glass is not an accurate means for determining that the refrigerant is correctly charged. That is what the manual is telling you. This is common knowledge. This is also why many manufacturers have eliminated site glasses from R134 systems.

that would be stupid. Just a quick look recently through the peep window was enough to confirm that there was no refrig left in a system refusing to cool. Good to know... Yes, could have hooked gauges and all, but didn't have any in the middle of the mojave...