Hi folks. 2000 Disco II. One of the bolts on my ac compressor hoses apparently wasn't galvanized and corroded itself to pieces, and unfortunately I couldn't get the remainder out without messing up the threads on the compressor. I got a used compressor off ebay not caring whether it worked so I could simply take the hose mounting off of the eBay one and put it on mine.

Of course my package arrived and I was excited (it being so hot) so I just put the eBay compressor in. I vacuumed the system, added oil, then started adding r134. I have one of those gauges that comes on the top of the bigger bottles of r134a.

I added two bottles. The low pressure is reading 35 with the system on low/max. When I turn the system off, it goes to about 85. According to the instructions I should be at 45 to 55 since the ambient temperature is about 85. It doesn't want to go past 35. Should I keep adding freon?

I am pretty sure I don't have a leak because having turned everything off for about an hour I don't feel any cold anywhere, and the pressure is not going down.

Thanks!

Charlie V

 

Sorry, when I say I added two bottles I mean a total of 24oz.

 

The low side pressure will drop as you add more Freon.... until you get the right amount. If you keep adding more at that point you are messing up.
You should be near 26-30psi on the low side, depending on outside temp, engine RPM and how you set the controls in the truck. This of course is over simplified but it sounds like your close to getting it.

 

Hmm. Maybe I went over. I wasn't aware that it would drop as I added it. Should I vent some until it rises?

 

No, the full portion for a front air only is 700 grams, a 12 ounce can is 340 grams, and you loose about 30 grams in the charging hoses per meter.

Which instructions say 45 - 55?

 

Before charging the system, did you put a/c compressor oil in the lines. if not you will have problems.

 

Sorry, I missed the part about new compressor. If the lines were open to air for any period of time, or old system was open to air, the drier will be toast. That's why they come shrink wrapped, a few minutes of air exposure and they have absorbed all they can..... most new compressor warranties from parts stores are based on a new drier at same time.

 

So, basically, I need to order a new drier and start over with the freon. Right? Is there any way to test the efficiency of the eBay compressor before I commit to it over my old one?

 

Nope, you most likely don't have access to the different gauges and such and nitrogen to test with. R134a is $10 a can at WalMart.

 

One more item worth mentioning. Did you charge the system under vacuum? You're sure you didn't break the vacuum prior to adding the refrigerant?

High low side readings indicates non-condensables are present in the system. Replace the dryer as mentioned above, pull another vacuum (run the vacuum pump for at least half an hour to be sure the system is completely evacuated), recharge the system w/ the proper weight of 134a.