any more to this?? so do you think the compressor is bad or do you think we might have a leak somewhere else? Our understanding is that with 134a, the high side pressure is right where we want it to be...are you thinking otherwise?

anybody else have any input?

 

I dont know much about A/C, except that I dont like it when it doesnt work right. ...

Sounds like your compressor is pushing HARD against a restrictive flow like a bad TEV or crimped line which would explain the low suction maybe ?

http://http://autorepair.about.com/cs/generalinfo/a/aa060301a_3.htm

 

Under normal conditions with R12, on this vehicle, the compressor would never see more than 230 psi high side pressure, you are approaching double that.

As I said before, these compressors will NOT hold up to 134 for very long at all. You did a good job getting the line fixed and fixing the leaks. A high, high side pressure along with a low, low side pressure usually indicates restriction between the compressor and condensor, but it also could be elsewhere.

Also, as I said earlier in the thread, getting the charge right on any 12 system converted to 134 is tricky. Overcharge might be part of the problem.

Honestly, this is NOT a good candidate for conversion. You would be money ahead to put your money and effort in fixing what you have, flushing the system thoroughly, putting in a new filter drier and going back to R12. That would be WAAaay cheaper than beefing up compressors and all that stuff so that you can save a few bucks on refrigerant. Do the math. Does it sound more economical to spend hundreds of dollars so that you can spend $50 less on refrigerant? If you're going to do it, you need to do it now, before the compressor is toast.

It's your truck. You need to make your own decision and you are free to do so.

My $0.02,

 

greg...thanks for the info buddy.... hope all is well...sent you an email yesterday.

MB Diagman....thanks for the more detailed response this time...it was much more helpful than your previous response. I'm not trying to cut any corners or anything...just taking what I have and trying to get it to work.

does "A high, high side pressure along with a low, low side pressure usually indicates restriction between the compressor and condensor, but it also could be elsewhere." mean that you think the hose we replaced could be part of that restriction? is there a way we could check this?

we know that they sell a flush to do this, but how do we go about the whole process? any tips to doing this would be apprectiated. I'll also so some searching on the forum to see what I can find. because of all the pressure the compressor has been under, is there anything we can do to test the compressor's status?

thanks for your help!

 

I made up a ac flusher from small old ABC Fire Extinguisher. I removed gauge and made that my air in to push cleaner.The exit nozzle is where, I clamp a hose to from the system. I Unscrewed top and added flush cleaner hooked up air and push down on top lever to discharge cleaning flush short or long shots of flush. Put a catch can on the other end of open line. I didn't have a air compressor so I used a CO2 tank to push it through my systen. Worked geat for me.. My 2cents It's not if your system will fail, but it's when...
orich

 

You have a restriction in your txv. The way you figure out how much R-134a to add to a system is weigh in 80% of the R-12 charge amount. When purging or flushing your A.C. system, use nitrogen. Nitrogen will absorb moisture which is the number one enemy of newer refrigerants. The oil used with all refrigerants. (ecspecially R-134a) have an extremely high affinity for moisture. When you have moisture in a refrigerantion system, it turns into acid. After fixing all the leaks and replacing any bad parts, purge the system with nitrogen, presure test for leaks and then vaccum down to below 500 microns. Purge a second time and repeat vaccum. Then weigh in your charge and take high side temp and pressure. Using your measurments and pressure-temp chart make any final charge adjustments.

If you want my $.02 Stick with the R-22. It is a more efficient refrigerant and will cost you less it parts in the long run. Plus you don't have to do a double evacuation like above with R-134a.

 

thanks for the input guys....we kind of thought the restriction might be in the txv.

 

R22?

If you have compressed air, here is a way to flush without having to come up with aparatus:

The restriction could be the expansion valve, but it will not usually show such a radical pressure difference. The good news is that they are cheap. When replacing it, make sure that you get the copper sensor line way up in the evaporator core or you will have icing problems. Check the line from the compressor output to the condensor. Make sure that the service valve is fully back seated after charging.

Get a can or two of Brake cleaner. Break all connections. Blow brake cleaner into each line, one at a time and then blow it out THOROUGHLY with compressed air. Do this to ALL lines, the evaporator, condensor and expansion valve. Get new o-rings for reassembly and coat them with refrigeration oil for assembly. The key is to make SURE that you THOROUGHLY blow out the flushing agent(brake cleaner.) Dump the oil out of the compressor and rinse it with just a little refrigeration oil. Do not rinse it with solvent. Find most any old car book and it will have a diagram for making a dip stick from a piece of wire for use in properly filling the compressor with oil. The oil does not circulate in these systems the same as it does in most later type systems.

After thoroughly flushing and thoroughly removing the flushing agent, connect everything back with the new o rings and put the new filter drier in place last and seal it up. Then evacuate and charge with R12 until the sight glass is clear.

If your compressor is still good after the stress test that you gave it with the 134, you should have cool air.

 

MB Diagman...
thanks for the flushing advice...I've been reading thru the certification manual for the 609 cert to buy R12 today when it was slow at the office...talk about a great sedative!...I'm going to go online and pay my $15 and take the test. We're going to undo all the 134a fittings and replace everything back with R12. Hopefully the compressor is still ok. Do you know of anyway to test it prior to charging it all up with R12? the one good part about the 134a is if you continue to have issues (which we have), at least its cheap enough its not that big a deal to have to buy more to recharge. Can't say that about the R12. Any advice as how to check the compressor would be greatly appreciated...just don't want to throw money out the window having to recharge the R12 because of problems.

thanks for all the help and I'll report back our progress!

 

ok...so the first part of restoring the R12 is done...just went to www.macsw.org and took my online certification test...I am no offically able to purchase the R12 myself.

 

--update --

ok fellas....I know its been a while since the last time I posted on this thread...but between waiting on parts and life getting in the way...haven't been able to post back til now. so...here's the deal.

we evacuated the 134a completely. took apart the whole system. found several places it had been leaking. replaced some hoses, replaced the thermal expansion valve, replaced the condesor (it was leaking too), replaced the drier, flushed out all hoses and parts...put it all back together. pulled a vacuum on it. The vacuum held at 30 for well over 30 mins. refilled the compressor with oil...as well as the condensor...recharged the system with freeze 12 (i know some of you said bite the bullet and go with R12...but in everything I found it was the same efficiency wise, pressure wise, etc, etc....and were over $20/can cheaper. the quotes I as getting on R12 were $29.99/can. the Freeze 12 was $6.46/can. Got it all charged up had the pressures where we wanted them on both high side and low side. the temp at the vent was a frosty 41 degrees...and it was all good. when closing the valves, the high side started leaking some (we knew it was weak...and it had shown signs before of not lasting much longer). after we got it sealed shut, it appeared to be ok. drove to work the next day...all good. leave for lunch...and all of a sudden it won't go below about 60 degrees at the vent. the compressor has condensation all over it, the low side line is all nice and cold and frost on the fittings...the high side line is all nice and warm going to the codensor...everything appears to be "like it should"...just the temp at the vent doesn't get to where it should.

drove it for a couple of days to see what happens...nothing changes. doesn't blow any cooler at the vent than about 60 degrees....notice the high side shut off valve may be leaking slightly...so we order one (it'll be in on tuesday)...but even so, when we check the pressures today...still good...the temp still doesn't dip below 60 degrees at the vent....any ideas? it was great at the 41 degrees...cooled the cab down nicely...I think it would work great in these hot texas summers we have...but 60...don't think that'll do it. thanks for the help in advance...

 

~~ bump ~~

 

I hate to keep asking ( I did once before) but do you have a heater shut off valve in the hose going to your heater core? I had this same problem with mine and after installing a shut off valve it dropped my vent temps considerably. The vacuum controlled valve usually will not cut the water completly off allowing hot water to by pass it and warm your interior.

 

The ONLY way that we can help you diagnose the system is for you to give us; high side pressure, low side pressure and ambient temperature.

From that we can tell if the refrigeration portion of the system is working or not. If it is, then we can move on to the air handling portion of the system including the heater valve and fresh air flap.

 

I get 31 degrees out of my stock A/C with R-12.. Maybe the problem you have is 134A.