air conditioning

[1stgen4evr]

Is there a professional in the AC business on our forum. I posted in the second gen forum about a problem that I am working on involving a 97 AC. While I did get some response, I didn't get any answers.



The system failed when the high pressure switch malfunctioned and the (from new) compressor case burst. Now we have all new components (vacuum and pressure flex line, condenser, liquid line, receiver dryer, and orifice which is in the liquid line on the new unit from Dodge, and the compressor) with the exception of the evaporator.



Ignition off, the system shows pressure that reflects ambient temperature. As soon as the system is running and cooling, the high side goes quickly to the break off pressure around 480 psi and the low side gets to around 100 psi. Temp at the vents will only get to about 50 degrees. There is very frequent cycling of the compressor clutch.



While conventional wisdom says that the evaporator never needs changing unless there is a leak, doesn't the symptoms indicate a pluged (somewhat) evaporator?



AC professionals in a nearby town replaced (blew out) five compressors trying to solve a similar problem on a 97, (not the one I am working on).



Any thoughts would certainly be appreciated.



James

 

[Jdorfmeyer]

You need to get more air through the condensor to reduce the pressures and keep the compressor engaged. I use a 10" electric fan on the outside of the condensor on my 2001. It pushes air throught the condensor and keeps my pressures in check. The way I found out about this is that when I charged my system to the correct level my pressures were getting to high and kept kicking the compressor off. I put a shop fan that moves alot of air infront of the condensor and the pressures stabilized and the compressor stayed engaged. The radiator and intercooler on 2nd generation trucks block alot of the air the clutch fan brings in and the fan doesn't center on the condensor. Now my AC is cold when sitting at idle or going down the road. I used the power wire from the compressor to power the fan when the AC is on.

 

[RWWinslow]

Following the previous discussion - try the following:



While the truck is running with A/C on and doors open, place a small mister or sprinkler in front of the condenser and monitor pressures / temperatures - if your pressures stabilize, but your cold air does not draw down, then you have an evaporator that needs the external surfaces cleaned. If your cold air temperatures come down to the low 40's / high 30's then you probably need to adjust charge.

 

[Steve Graham]

Try these people, AMA Auto ac forum
The forum is free.

 

[Leper]

Your pressures are both too high. Are your cooling fan(s) working? Are they running the correct direction? Is the condenser gummed up on the outside? If you exploded a compressor, debris went everywhere it could. It can lodge anywhere, but it starts from the output hose from the compressor and goes through the system.



I am more used to imports that use expansion valves, not orifice tubes. There is such a tiny opening in the expansion valves that you wouldn't thing anything would get through, but it sometimes does.



Like stated above, make sure you are not overcharging the system. If there is a min/max spec, use the minimum possible. With your problem, I would put in just enough to make the compressor come on and check the gauges.



Also make sure that the compressor clutch is not staying engaged when the system cycles off. Its rare, but a sticking relay may keep the compressor on. In a vehicle with electric fans, if the clutch doesn't disengage, but the fans turn off, the compressor may blow itself to pieces in a very short while.

 

[TBurow]

i am an ase master tech and have seen this problem many times before, the pressure is too high due to a restriction in the system, pull the oriface tube and look at it since the system has been run for a while, it will either be melted or covered by a metal paste from the old compressor coming apart internally. you didnt say if the evaporator was flushed, if not alot of the debris was still in it. i recently had a car with a compressor failure that was repaired elsewhere and not flushed which plugged the drier and destroyed the compressor and condensor due to high pressure.



flush the evap, flush all the lines and condensor, and replace the drier and all should be well.

make sure to add refrigerant oil to the system before you run it as you will loose a large portion of it.

 

[1stgen4evr]

Thanks all. I have done all the things suggested with no improvment. WHEN it is fixed, I will post the solution.



James

 

[Leper]

Thanks all. I have done all the things suggested with no improvment.

James

I don't see how that is possible.

Either there is something still blocking the flow, or one of your new parts is bad. If the system was not flushed properly, the first time, all the left over junk will ruin all the new parts you install.

 

[1stgen4evr]

"I don't see how that is possible. "



I totally agree.



I realize that it is near impossible to diagnois without hands on knowledge. I was just hoping that someone had had a similar experience and knew something that I didn't. At the moment, I am out of money for more experimenting. It is fairly cool or at least tollerable, and I will get back to it later.



Just one more crappy problem.



James

 

[Don Tanklage]

i know nothing about a/c but i feel for you



you sound like you have had the same luck lately that i have been having



hope your luck turns around soon



don

 

[TBurow]

did you pull out the oriface tube again? was it plugged?

 

[1stgen4evr]

did you pull out the oriface tube again? was it plugged?



Yes we did and no it wasn't. We have had the orifice out/replaced about five times along with the other things that were done. There has not been any of those times, including the first, that the tube was actually clogged to any significant extent. I split the flex lines apart, nothing. It has been vaccumed an hour each time. I am not an AC professional but the guys doing the work are and get complete result all the time on other vehicles.



The original compresor only cracked the case and the freon escaped. Nothing has disintergrated as far as we can tell.



But I will eventually find out what the problem is.



Thanks all.



James

 

[dblake]

Have any of you guys thought about converting to FR-12 refrigerant . I did on my 2001 and it blows way colder now than it did with that 134 junk . Pressure on both high and low sides are lower also .

Refimax - Home

 

[1stgen4evr]

Once again we pumped the system down and pulled the orifice tube. Flushed with AC Delco fluid which is supposed to be the answer. Nothing has changed to any great extent.



But while reworking the system this time, I moved the orifice tube to the location I observed on a 2000, which is right outside the evaporator very close to the firewall. I went back to the original liquid line from the condensor to the 'adapted' orifice tube block. This required also to install a low pressure tap in the suction line just down line from the receiver/dryer.



I am getting eratic start up cooling first thing in the morning. After it settles down I get 40 degree cool which is pretty good for south Georgia.



The bad thing is that I am still cycling on the high pressure switch with readings at the cut off of 480 psi. I am now convinced that there is still enough moisture in the system (after about five draw down and vacuum cycles) to get ice in the orifice tube and thus high pressure readings. Next time, (soon) I plan to put another new dryer and vacuum for an overnight period.



James