A/C pressures

greg850r · Post by **greg850r** » 23 Jul 2019, 12:58

Hi all,

I have a 96 850 T. I charged the A/C and it had cold air for a day or two but leaked out and the compressor stopped engaging. The smell in the interior points to a bad evaporator, but it did hold 28 inches of vacuum for 30 minutes before I filled it the first time.
I had a little freon left in a can from charging another car and I thought I'd plug it onto this one to get the the compressor to run and see where it was at pressure wise. The gauge said 35lbs, which should have been just enough to get the compressor to come on but it won't unless I jump the plug to the low side switch. When I do the gauge immediately goes to zero. I'm thinking orfice is clogged. Thoughts anyone?

Post by **Ozark Lee** » 23 Jul 2019, 21:29

The kick out pressure is around 28 to 30 PSI but the kick on pressure is higher than that. Everything says that you have a leak since it was charged and now you only have 35 PSI static pressure. On a moderately hot day the static pressure would be at or above 100 PSI on a fully charged system - it is totally dependent on the underhood temperature at the time of the reading.

I think you know what you have going on, and it is a PITA. It is about a 95% chance that you have a bad evaporator. If you follow the guides in the repair database it is a doable job by a mere mortal but figure on a couple of uninterrupted days to do it.

...Lee

Post by **jimmy57** » 25 Jul 2019, 07:43

it takes 42-44 psi to get compressor on. The pressure cycling switch/pressostat opens when pressure falls to 22-25 and closes when pressure rises to 42-44. With so little refrigerant the compressor suction draws in the refrigerant and lowers pressure to near zero and the discharge pressure is probably 75-100 and it is unlikely there is anything wrong with orifice. When you do evaporator it is suggested that you separate line and remove and clean or replace orifice. The orifice has filter screen and there will always be something on it to blow off. when you put new parts in there is a good chance some filings and stuff from manufacturing are in the new parts and the orifice might be compromised with new stuff added to the existing stuff.

Post by **abscate** » 25 Jul 2019, 07:56

Have fun removing the orfice from the hard line on the car. I remembered I managed to do it with two open ends, but it was a serious Charlie Foxtrot

Crows feet with wobbles would probably work well, though.

Post by **erikv11** » 25 Jul 2019, 08:33

I found the orifice super easy to replace when I did it on my 96 850. Oh, there was no engine in the car ...

Post by **abscate** » 25 Jul 2019, 08:55

erikv11 wrote: 25 Jul 2019, 08:33 I found the orifice super easy to replace when I did it on my 96 850. Oh, there was no engine in the car ...

How are those front wheel bearings looking?

greg850r · Post by **greg850r** » 25 Jul 2019, 08:59

Thanks guys. I was kind of hoping someone would have an idea I didn't. My son and I did the evap and heater core on our other 96. We had pieces spread out all over the garage for 3 days. We think we can do this one in a day now but we'll see.

Post by **abscate** » 25 Jul 2019, 10:07

greg850r wrote: 25 Jul 2019, 08:59 Thanks guys. I was kind of hoping someone would have an idea I didn't. My son and I did the evap and heater core on our other 96. We had pieces spread out all over the garage for 3 days. We think we can do this one in a day now but we'll see.

The second one is faster, and the third. Then you hit the plateau

Good luck - at least in MO you have to have AC - it kills us to fix it when we need it for three days.