riddle me this? A/c Question.

[hcgamer88]

Okay so heres the deal I just recently under took an A/c conversion on my 92 mtx sho. After replacing all the lines, condenser, and dryer my A/c finally should a glimmer of hope and was blowing cold air. The low side pressures are right but unfortuantly the high side pressures run about 400psi to about 450. When I give the throttle enough gas to maintain about 1800 rpm the high side pressure jumps off the gauge to over 500 psi. So the car runs with a/c but if I am in alot of stop and go traffic the car tends to over heat. After doing some research about A/c's in general I made a few interesting discoveries I thought I would share with the rest of you. I did a search on this forum about a week ago for "high pressure sensor", but to no avail I only found certain threads where people say they have found the low pressure sensor but for the life of them they can not find the high side sensor, plz help!!! Well turns out that R-12 systems where designed without them because of different heat exchange ratio's. This is why the high pressure side of my A/c runs such a high pressure. Also this means that the A/c compressor is running over time and rarely turns off. In addition because the gas is expanding and condesing alot faster then it should be the radiator fan is having trouble cooling both the engine and the condenser. Heres my question Cold air sells a high pressure sensor for the taurus sho. Has anyone ever tryed to install this before and if so what did you use, Where did you make your electrical connections, or even if I am just blowing smoke out my ass and this wont even work. MAybe theres something else I over looked. I appreiciate any input thanks!!!


Stephen Prochilo

 

[rubydist]

did you vacuum out the system before you charged it w/ r134a?

 

[hcgamer88]

yes several times as I changed out alot of the parts at different times. No one has meesed with this a/c for about 4 years so we mostly did it y trial and error, but the company that sold me the conversion kit suggested the dryer and condenser as well. Although they mentioned nothing about the orfice tube which is pretty much the first thing you always look at with a/c systems other than the obvious like low levels of oil and gas. so idk how good there suggestions where. the only thing that is left are the lines in the cabin that go to the fire wall and the evaporater. The compressor is obviously working to be putting out 500 psi plus. So the chances of a restriction are slim, but on the other hand if what I say is true then anyoneelse that has done a conversion should have run into a similiar prblem. Like I said I did a search on this and havent really found any threads with similiar problems.

 

[projectSHO89]

If you have 500 psi in the high side, YOU NEED TO HIRE AN EXPERT who knows what he is doing.

You have something SERIOUSLY WRONG! You either have a high side restriction or are seriously overcharged.

 

[hcgamer88]

hmmm well I work at a private shop and this isn't just me working on this car. The guy that actually owns it has a mechanical engineering degree and a electrical engineering degree and like I said almost everything has been replaced over than the evaporator and the compressor it self. I mean if you say its seriously off then they next thing to change is the evaporator no?

 

[Sholovenothate]

I have an engineering degree but I didn't learn HVAC systems on cars =p Wyotech would have sounded better =p

 

[projectSHO89]

Just because he's school educated doesn't mean he knows what he's doing in this situation.

Find someone who has an honorary degree from the SHK (School of Hard Knocks) with practical experience in R12/R134a conversions.

 

[itwonder]

The high pressure indicates the condenser isn't or can't do its job. Is anything blocking condenser airflow? The system could be way overcharged. It could have way too much oil or mixed/bad/wrong refrigerant. Did the oriface get left out?

 

[jelloslug]

It sounds like a clog to me.

 

[rubydist]

If the system was properly evacuated prior to charging, and if you put in the proper amount of refrigerant, then the high side pressures being too high tell you that the orifice tube (expansion valve) is plugged or partly plugged and is not allowing the refrigerant to pass at the proper rate.

I would change the orifice tube.

 

[hcgamer88]

Like I said everythings already been replaced including the line with orifice tube built in (it now has that fancy Vov). The only thing I havent cracked into yet are the lines within the fire wall and the evaportor. O and the output line from the compressor (the line that looks like it has a mini dryer on it). Also the dryer that was replaced with a four seasons dryer and said it required .2 lb less of refrigerant. We started with I believe 8 oz of oil and 2.2 of refrigerant I think not exactly sure. All I know is the first couple of times the pressures where way to high, we reset fined tuned the amounts of oil and refrigerant and got it to a point to were it should work. Also i'd like to add that even tho the a/c works i havent been running the car with it on. I mean i really only have 2 options left as far as replacing parts in the system. Is it possible the A/c machine I'm using is not working properly? I really doubt it though cause im down in Florida and the majority of our business is a/c work. The only car to ever really give us a problem is my car go figure.

 

[rubydist]

the compressor would have had oil in it. if you added 8 oz more oil, there is too much oil in the system.

 

[zak]

Did you flush the evaporator? Flush (or at least drain/purge) the compressor?

Did you use a new liquid line with the correct orifice calibrated for R134A? A "replacement" 92 line would likely be set up for R12.

If you did not thoroughly clean out the unreplaced parts you could have black death.

 

[MADDOG11]

I would tend to agree with a restriction! Maybe the condensor or the evap core!

 

[projectSHO89]

How much R134a was installed? If the original factory spec was 2.2# of R12, and you installed 2.2# of R134a, you are severely overcharged.

Did you install one of those POS VOVs instead of a stock liquid line with the correct orifice tube for R134a? Is so, that's another thing likely to affect the system pressures even if properly charged.

Serously, find someone who has an honorary degree from the SHK (School of Hard Knocks) with practical experience in R12/R134a conversions.

 

[SideSHO09]

that high pressure switch you are talking about for a converted 12 to 134 system is on the passenger side near the front headlight and has 2 plugs that merge into 1 and are connected to the low pressure switch on top of the accumulator.
Im not sure what they are wired to from there but one plug from the high pressure switch (near headlight and battery) plugs into the low pressure switch on the accumulator and the other plug is plugged into the factory r12 plug that would have plugged into the accumulator from the factory.
the 3rd plug is plugged into the high pressure switch that goes into the condensor. The line that is on the passenger side between the battery and headlight.

Thats how mine looks and it was converted by Ford dealer in '98.

 

[rubydist]

The wiring on that high pressure switch just interrupts the signal from the low pressure switch. The high pressure switch is normally closed, so the system works normally, and the switch opens when it sees pressure too high.

 

[hcgamer88]

so your saying that the one plug I thought was the low side is actually both the high and low pressure switch?

 

[Bill Strobel]

With high side pressures approaching 500# you have a restriction somewhere. The three common places for a restriction (usually due to debris after a Ford black death compressor failure) are the orifice tube, the condensor, and the evaporator.