A/C issue

[Snapshot]

Hello everyone, it seems like I'm stumped once more on my Expedition (2000 XLT, 4x4, 170k miles). I have had my vents blow smoke before, but this is something different. I think this time it's steam instead of smoke; it's colorless and odorless. It will only smoke whenever I have the A/C on and the temperature on cool. Once it starts smoking, I can turn it over to warm and it will blow a lot more for a few seconds and then completely stop. It won't start back until I get it anywhere back onto the cool side. So, any ideas?

 

[stamp11127]

Check the outlet temp at one of the vents when this is happening. Units that are low on refrigerant will tend to freeze the evap and blow a white vapor from the vents. You can also check the accumulator to see if it is icing up along with the lines.

 

[IMINYOURCHAIR]

Check the outlet temp at one of the vents when this is happening. Units that are low on refrigerant will tend to freeze the evap and blow a white vapor from the vents. You can also check the accumulator to see if it is icing up along with the lines.

for that to happen he would have to also have a failed LPS (low pressure switch) this would allow the compressor to suck enough refrigerant out of the evap to cause the temperature to drop below freezing.

you can't charge by pressure when the ambient temp is below 75 and not at all when it's below 60. if you can get a set of gauges get them on when it's warm out and watch the low side pressure. shouldn't be too far past 50 (high) or lower than 25 or so without cycling the compressor. the service dvd says The electrical switch contacts open when the suction pressure drops to 152-193 kPa (22-28 psi).
The contacts close when the suction pressure rises to 276-324 kPa (40-47 psi).

if your system is under what I would call a "nominal" load, you should expect the low side pressure to be close to the cut off point of that switch when you have the engine at 2k revs. high side should not be much higher if at all, than 250, the high side safety switch operates at 420 psi and closes again at 250 psi. this one will open at idle if you have a bad clutch fan. ( mine does, simple test is if it starts to cool again when moving faster than 20 mpg)
all in all, I can speculate all day what's wrong but it's useless without pressure readings. I will also need to know within 3deg the ambient temperature of the outside and inside air to see if the pressure you have is okay

 

[IMINYOURCHAIR]

also, has the system ever been opened before? has it been recharged either that you know of?

 

[Snapshot]

The system was recharged back when I first started driving it. I'll be able to go to the store and pick up a set of gauges to check out the pressure. I haven't had time to do much this weekend due to work. Boss-man said he needed me to work double shifts yesterday and today, so it's been hell.

 

[IMINYOURCHAIR]

I know how you feel, I got 50 hrs last week and I am looking at another 50 this week, too bad that's going on two diff paychecks...

since you say it's been recharged it could be overcharged or it had air in the lines from the manifold gauges. if it has air, it will need to be recovered, pulled down to a proper vacuum then charged after purging the gauge hoses with freon before connecting them. I have had a couple friends to that this summer when they replaced a hose and tried to charge it w/o a vacuum. and another just didn't purge the lines.

 

[IMINYOURCHAIR]

if you can't get a day above 70 to check the pressure this year, you may have to wait till next spring to get a proper charge unless you want to start from zero and charge by weight. that's what I had to do when I installed a compressor and used manifold lines where the PO had them removed and had a B/P pulley in place.