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A/C Fixed - Sort of

Dan D

Well-known member
Joined
Feb 27, 2001
Messages
1,171
Location
Brownsburg, IN
My car hasn't had working ac in 10+ years; never bothered to fix it. I was tired of basically parking it for the summer since I moved to Houston 6.5 years ago so when i had everything ripped apart for the motor/trans rebuild, I went through the whole ac. I replaced every o-ring, put on a reman compressor, pulled the evap and changed the expansion valve, tested all the sensor and rewired a few of them.

Yesterday I changed the drier, pulled a vacuum on it for 30 or 40 minutes and then charged it with 26-28 oz of R134. Everything works, but the outlet air temps are not very cold - 65F while driving (97F outside), 70F while sitting in the garage (it was 102F in my garage yesterday). While at 1500RPM in the garage, the gauges read: Low = 35psi, High = 250psi. I kept adding refrigerant slowly while watching the thermometer in the vent. It kept going down some as I added and then became stagnant at 70F so I stopped.

A few years ago, I was fixing a stripped radiator mount hole and while drilling I hit the condenser - psssss what ever R12 was left at the time when bye bye. I had it welded shut, but I'm not certain that the welding didn't obstruct one of the two flow paths through the core. It seems to me that if that were the case, the condenser’s capacity is cut in half and I would not be able to get as cold of temperatures for a given charge?

Can one of the A/C expects verify my reasoning. Is there something I can watch for on the gauges that could confirm my suspicion? Should I just try and add more R134?
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Shoot the condensor core with a digital pyrometer with the system operating and fans running.

Any restricted areas of the core will show colder than areas with more flow.
 

Dan D

Well-known member
Joined
Feb 27, 2001
Messages
1,171
Location
Brownsburg, IN
Excelent idea. I'll try that. The core is basically two sets of tubes snaked around. Every other row changes tubes. If row 1,3,5 are different in temperature than 2,4,6, etc. I need to replace the condensor.
 

Romanova

Well-known member
Joined
Aug 7, 2002
Messages
3,855
Location
Cypress, TX
Dan, I'm going to put you in charge of fixing the AC on #490 when the time comes sir. /ubbthreads/images/graemlins/crazy.gif
 

Thanks for giving up the R134 numbers. You seem to be right on. I went with about 28 oz on an empty system using math. Now I know I got pretty close
 

I have R134a that blows cold and on Tuesday I can hook up the gauges and see what pressures I'm seeing. It's been awhile, but if I remember right on the initial charge I got over 200 psi on the high side, but had to let some refrigerant out because it wasn't very cold. How much over 200 I can't remember.
 

SouthCaliVR4

Well-known member
Joined
Jul 31, 2010
Messages
984
Location
North county San Diego
My 2psi, your high side press is well.. high. While I still have r12 in mine I do a lot of 134 conversions, I find temps on various cars to be best around 25-35 low side & 150-175 high side. But then I don't think I have done a mitsu system conversion yet.

I still have ready access to r12 & will stick with it as long as I can but am able to get some pretty good temps from the converted 134 systems I have worked on.

just to put it out there, the mineral oil used in r12 systems is incompatible with r134a systems & the pag oil that should be run. it turns to a nasty gel if the two are mixed. It's important to clean the system thoroughly with some type of a/c system flush solvent. it will work if you don't but the compressor can fail prematurely & the gel can plug up expansion valves.
 

Dan D

Well-known member
Joined
Feb 27, 2001
Messages
1,171
Location
Brownsburg, IN
Thanks for the input. It didn't even start to get cold until I had put all of the second can (24 oz) and I went slow from there so I don't think I overcharge, but I'm no a/c expert. The rule of thumb I read for R134 high side pressure is 2.5 times the ambient temperature (102 * 2.5 = 255). I don't know if there's any truth that. Would a partially blocked condenser cause a high high side? I'll try and go check per Toybreakers recomendation today and see if I have a problem.

I did make sure and the conversion the right way since everything was apart. Every piece was cleaned with brakleen and blown out. The reman compressor was drained and then refilled with Ester oil to the full system amount spec'd in the manual. Even with it not blowing super cold, I ran a couple errands with the windows up yesterday and A/C on and wasn't sweating - that's a damn miracle in this swamp!
 

I just hooked up the gauges to my car and I'm getting 225 high and 35 low with the compressor on. Vent temp is 50 degrees and outside temp is in the 90s.
 

SouthCaliVR4

Well-known member
Joined
Jul 31, 2010
Messages
984
Location
North county San Diego
Just finished servicing a 134 system. Granted this is an actual 134 system. Ambiant temp upwards of 87deg low side reading 32 high side reading 160 dash temp 41.
 
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