A/C sensor...where is it!?

[ICrushedAPrius]

I have no A/C in my 1998 EB 5.4L.

The fuses are good, the lines in and out have pressure, the schrader valves aren't leaking, and the compressor pulley will turn for a second and a half, then stop for a full second...continuously while the A/C is switched on. My Dad, who was a Dodge mechanic for years, says the "orifice valve" would usually be the problem. anyone have any ideas? I also unplugged the wires from a sensor on the aluminum line by the radiator to test. When I switched on the A/C nothing happened..no whirring or anything. so it is not the sensor. Please help! It's hot in NJ!!!!

 

[walnuts4x4]

so what exactly is happening with A/C does the blower fan still work or is it just staying hot no matter what setting you have it on? Mine was the blend door... no matter what setting it was on all I had was hot... took out blend door actuator and pieces of the blend door fell out... instead of replacing with oem blend door I am getting a heatertreater door... but if I'm off topic sorry just ramblin about what happend to mine....

 

[ICrushedAPrius]

The air is the same temp as the air outside. it's like having just my regular vent on. The compressor tries to turn, and the lines are charged. i don't get it. It blows full force, and is not blistering hot or anything, but it is def.not A/C...

 

[walnuts4x4]

yeah mine was blazing hot... do you have electronic temp control EATC or manual control? the EATC has a self test you can do sometimes will tell you what is wrong if its electronic....

 

[ICrushedAPrius]

I'm assuming the "manual control" is what i have. knobs...no electronic readout or anything.

 

[ELVATO]

If you have proper pressure in the low side, then it might be the low pressure switch? It seems to happen to the Mustangs a lot.

It's the switch that opens when there isn't enough pressure in the line. What you do is manually "close" the switch to test if the compressor will turn on. Hold up, lemme try to see if I can find it.

This is what it looks like:


Description:
-A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
-This allows the suction pressure inside the suction accumulator to control the operation of the A/C cycling switch.
-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).
-When the A/C cycling switch contacts close, the A/C clutch field coil is energized.
-When the A/C cycling switch contacts open, the A/C clutch field coil is deenergized and compressor operation stops.
-The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
-This prevents icing of the A/C evaporator core and blockage of airflow.
-It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.

I'd imagine that shorting the pins to the connector that goes on that would simulate a "closed" situation. The compressor should engage as long as you have it shorted. Don't do it for too long, though.

Also, are you sure you have the proper pressure in there? Remember you have to do it with the vehicle running and the AC set to Max A/C. If you do have proper pressure, and the compressor engages with the shorted contacts, then the switch probably went bad. I think they're like 15 bucks for a Mustang one, so I can't see the Expy one costing much more.

 

[ICrushedAPrius]

great, I'm gonna check that out. I can't see anything that looks like that, but didn't have much time to search. The majority of the system is crammed against the firewall near the main fuse panel/ starter solenoid posts. thanks a lot for the info, I'll update when i can. Also, I'm not sure about the pressure, but the schrader valve on the low side sprays fluid and the other shoots out air...I just assumed the lines were charged then.

 

[ELVATO]

Go to autozone/advance/any autoparts store, and get a recharge kit that comes with a guage. If you are low on pressure, the compressor will just cycle.

That's what was wrong with my roommate's Mustang. It would always "surge" as the compressor engaged/disengaged, and his AC was hot. We measured the pressure, and there wasn't enough. Filled it up, and now he has cold AC again.

It was while I was reading up on Mustangs that I found out the low pressure switch fails a lot on them.

As for the switch itself, look along the AC lines for something with a two wire connector coming out of it. One of those should be the low side switch.

But first, measure the pressure. You may just need to top off.