1996 f150 2wd with the 4.9
Freon level is good and has been good. Compressor doesn't come on when air is turned on so I jumped the low pressure switch today and the compressor came on.

I'm lost from here. What do I need to look at next? Replacing low pressure switxh ?

Thanks

 

What was the high and low side pressure before you jumpered the low pressure/clutch cycling switch?

 

I don't remember. I don't have a way to check high. Checked low with my Freon can gauge and it was 2 marks from being overfilled but still in green.

 

Without empirical numbers is pointless to go any further. You might have a bad low pressure switch or low on charge. A set of real gauges is your best friend.

Since the fill kit has no numbers on the gauge it's tough to tell what is going on. The high and low side equalize when the system is not energized so I suspect the equalized pressure is enough to make the cheapo gauge happy, but once the compressor engages the low side gets sucked down enough to trip the low pressure switch off but there is not enough charge to pull the switch back in until the system is off for a long enough period of time (minutes/hours/etc.)

 

What gauges do I need to get and since the compressor doesn't kick on , will I need to jump it when I have the gauges hooked up?

 

Ok, jumped the switch, and had my fill can on it and when the compressor came on it pulled the gauge to 0. So guessing I have a leak. Do I need to replace the switch as well?

 

A real A/C manifold gauge set. The cheap Harbor Freight brand are adequate IMHO.

The real equalized pressures will reflected on the gauges.

 

You are low on charge so it could be a leak. Now you need to evacuate the system then pull a vacuum to see if it holds. At this point....may be time for a pro or a serious crash course in automotive A/C.

 

R134a depends on pressures at certain ambient temperatures. To determine if your system is "full" and operating properly, you need a proper AC manifold gauge set. You need to check the high and low pressures.

Refer to the chart:


Jumper the pressure switch to get the pressure to run. Check the pressures. Give it a few minutes to get up to full pressure on the high side.

Check back with us if you have issues.

 

No, the switch is good. It did what it is supposed to do by not allowing the compressor to turn on. You don't consume refrigerant so there is definitely a leak in the system unless it has not worked since you have owned the truck and was not properly recharged in the past. You can find some leaks by looking for the dirt around hose connections and other areas because it sticks to oil that will also leak out with the R-134a. I would replace whatever is leaking (o-rings, compressor...etc) and then see if the system will hold vacuum to check for other leaks.