98 Silhouette A/C not working

Just bought the wife a 1998 Silhouette and the A/C is not cold at all. The dealership said that they tried to charge it, but couldnt get it to take a charge. I personally think they didnt try. Do these cars (Venture as well) have issues with the A/C?? Do hoses leak, or a bad condensor?

I owned a 99 for almost 8 years. We enjoyed the ride.
Only one problem with the A/C. It developed a leak at the seal on the muffler hose where it attached to the compressor. I don’t know if that is a common problem or not. It is common to develop a leak somewhere in the system & lose freon. If the pressures are to low the system will not operate. There is a pressure switch that has to be made for the compressor to engage. One common place on for leaks on automotive systems is the compressor shaft seal where it connects to the pulley. The seal will get hard & brittle with age & from the heat. Sometimes they will leak during the winter when the seal is cold & less flexible. If you have access to A/C gauges & a vacuum pump it should be easy enough to diagnose the problem. It may or may not be low freon. It could have other issues. If you don’t have equipment to check it out, you may have to take it to a good independent shop. Any competent shop/mechanic with the proper tools should be able to find the problem. One quick check you can make; check to see if the compressor is engaging when the A/C is on. If not you can jumper the pressure switch. If it engages then you are probably low on freon. But you still need to find the leak.
Hope this is some help.

Does anybody know the location of this pressure switch on a 2000 Silhouette? I want to bypass mine for testing but haven't found it yet.

Thanks!

Don't try it!! That is not a switch- it is a pressre transducer- you have 3 wires- and risk popping the ecm if you try jumping them--switches have 2 wires- and were discontinued in early 90's- and only used on CCOT (cycling systems)- yours is a variable stroke compressor that is designed not to cycle.

The system is designed so that when it sees 47 psi, the compressor will come on-- 65% of all automotive a/c failures are due to loss of refrigerant- you need to put a guage on it- if you see positive pressure, add enough refrigerant to make the system come on. If it is dead flat- no pressure- you need to pull a vacuum first-- and see how big you leak is....Number one leak location is compressor shaft seal, followed by compressor body o-rings.

They just had to go and make things more complicated by getting a computer involved...

I put gauges on it and it's flat. Pulled a vacuum on it and it holds a vacuum overnight so if there's a leak it's small. Tried putting gas in it with system under vacuum and it would only suck in about 1/2 of a 12 oz can. Don't recall what the suction side pressure was but it wasn't anywhere near 47 psig. In fact, 47 seems pretty darn high for this setting.

Any thoughts on this? A/C was working just fine last fall.

Can you explain this variable compressor thing? What exactly is varying? I could see bypassing some of the hot gas back to the suction side under reduces load but wouldn't this require some sort of modulating 3 way valve?

Thanks!

The V-5 comressor varies its displacement from about 5% to 100% - the piston travel is less with less demand= all based on suction pressure and a control valve that allows the crankcase pressure to destroke the pistons- V-5 came out in 1984- so it is nothing new.....

Computer is involved so as to shut down cooling fans when not needed- like when running down the road and to also do low pressure and high pressure cut-outs- all in one convenient transducer.

If the compressor runs all the time and it's the piston stroke that varies, is there any way to make the clutch engage and force it to run long enough to get some refrigerant into the system?

And is 47 the high pressure cut off? I thought R134 systems usually ran somewhere in the 25-30 psig range on the suction side.

Thanks!

It takes 47 psi static pressure (a/c off) for the compressor to even engage- so with that in mind just dump your first can in and what the pressure rise above 47 (high side) and the compressor should kick on by itself. Remember, you are dumping into the low side- the transducer is on the high side of the system, it may take a bit for the high side to equalize. It will not shut off compressor if suction runs 25-35 psi.

If I wanted to "jump" something- I would jumper the a/c relay in the underhood fuse box-- then the compressor would come on- a whole lot easier than trying to run a test lead down to the compressor..

High pressure cut-off is 427 psi---

OK - I was under the mistaken impression that the low pressure sensor would be on the low side. 47 psig low cutoff makes total sense if it's on the discharge side. Thanks for clearing that up.

And thanks for the tip on the A/C relay. I'm guessing the coil on this relay is normally energized by the ECM based on whatever it 'thinks' of the pressure transducer reading.

Now keep in mind that the R134 pressure does not depend on the quantity, but rather on temperature. See table here
http://dodgeram.org/tech/repair/HVAC/R134a.htm
As long as you have enough R134 in the system so that some of it is in liquid form, the pressure will be according to that table. THis is not the "law of gases" (which happens when more and more gas is forced into a fixed volume) , but rather "vapour pressure", that happens when a fluid is in equilibrium state with some of it in liquid state, and some of it in gaseous state.
I do not know what is the outside temperature in Denver at this time, but I suspect it is not that high in the morning and if the engine has not been running to develop some heat around the place, the actual vapour pressure can be lower than 47 psi and all is normal....

As long as your a/c system has been evacuated , you can transfer all the refrigerant needed without the engine running as long as you keep the refrigerant bottle at a higher temperature (hence pressure) than the system...and that is easily done if you do it with engine cold, and keep the refrigerant bottle immerged in a warmer water bucket. Evacuating the refrigerant cools down the bottle so it rapidly falls down to a lower pressure than the system you want to fill up, hence halting the transfer.
...keeping a relatively large water volume at mild temperature will push the gas contents into the system. I've done that very successsfully sveral times and it is much less of a stress not having the engine running in your face.