I am referring to a Komatsu D39EX-21A , but I think this applies to all machinery. I cleaned my filters the other day and checked the site glass , it was showing liquid in the glass. I put a gauge on the low side and it was showing 20lbs or less. I thought it was a touch low so I added a little 134. That afternoon when it got real hot about 95 it quit cooling , the vent temperature was 80*. The manual says the filter dryer should be changed every 2 years. I was thinking about washing out the evaporator and the condenser was washed out about 2 months ago. I'd like a little input on what to look for before I ruin a compressor. I did check the low side when it seemed to quit cooling and it was way high like 60 lbs. The system has the yellow leak dye in it as well. It don't seem to be leaking.
What is the high side psi. What is the temp going to the evaporator.
I have a heat gun and will check it Monday. I can check the high side for temperature. I use to be a HVAC tech , but the automotive stuff is a little different. I read the manual about changing the filter/dryer every 2 years , I thought I might do that then weigh the charge in to make sure it has the correct charge. I'll also check the high side pressure as well. I know when it gets 95 and the sun is beating down it will warm up some, but 80* out of the vent doesn't seem right. It cools good in the morning , I wonder if it is overcharged as well. I do know its the wrong time of the year if it completely fails.
im no a/c expert by any means how ever i can usually get by, run it with the guages on and see what their at. low and high side? with ac on and doors closed what the vent temp after 15min? a dial therm. usually works best for me. if it had 20psi when it was off that sounds low, i think normally its around 60's?, i wonder if your low pressure sesnor is kicking it out?
If you go out after the sun gos down and it works then you probaly got to much in it and the high presser switch made the compresser clutch kick out. I worked at a shop years ago and the boss did all the ac work. I could see it was not a good thing to be into. He gave me a book and i cant find it but it had several pages of gauge readings telling what they meet.
You have to head pressure, from to much freon or lack of air flow across the condenser I would guess. Weighing it in on good vacumm is the only was to go because gauge readings are not always definitive.
well said!!! I would check the evaporator also
Here is a link to site that has a training manual for AC, there is some good information in there that might help you out Chapter 8 has gauge reading in it. http://www.rdac.com/sites/default/files/Service Manual.pdf It opens as a PDF file Or go here http://www.rdac.com/resources/product-literature This is where I got it from. I print this off for every apprentices at work all the time, great book.
I checked it over a little today , the suction pressure was about 62lbs this morning with outdoor temp being 80* and cab temp was 84*. I decided to take some gas out , let the suction pressure down to 50 or less. I checked the site glass and it started showing bubbles , I think the system may be contaminated and need to be vacuumed and recharged. It has a lot of leak dye in it as well. The condenser fan is running and the evaporator looks clean , there is dust in the evaporator compartment. I think I might change the filter dryer as well. One thing , this afternoon it was cooling better. I will get a proper set of gauges when I recharge it.
Just a little info to share on this. I pulled a vacuum on the system for about an hour. Recharged it using a 134A chart, as well as an approximate weight. Its blowing 50* when its 90* outside now. I believe it has some moisture in the system.
If it has that much moisture in it, you need a new reciever/dryer. If it has an orifice tube, pull it out and look at it. If it has a bunch of "stuff" stuck to the outside outside of it, replace it too because ,chances are the dessiant bag inside the dryer let go. With the dryer off and, the orifice tube out, unhook the compressor and flush the system real good. Remove compressor, dump the oil into a measureing cup, and add enough oil to meet recommended amount. Should take either Ester oil or, PAG10, not sure which. Reassemble, pull vacuum for at least 30-45 mins. Recharge. Old timer told me a good ,general rule of thumb is, high side=twice the outside temperature plus 10%, low side should be 30-40lbs. Again, those numbers are general, I'm sure someone will chime in on the exact numbers but, those WILL get you real close. Hope this helps!! P.S. I always try to charge a system at hi idle.