Need some help finding what's wrong with my A/C on my 2007 f150. 4.6L
My A/C compressor is cycling on and off about every 6secs. The gauge reads 100psi with truck off and when I start the truck and run the a/c full blast it drops down to about 20psi then the a/c compressor turns off and the psi rises up to about 55psi then the pump tuns on and it repeats the cycle of going back down to 20psi shut off an rises back to 55psi turn back on

Can it be low on freon or do I have a faulty pressure switch. If it is the switch can it be changed with out losing the freon.

Thanks in advance.

 

That's probably a low charge. Your pressure switch is doing its job.

Please don't take offense to what I'm about to say.

If you had to ask that question, you don't have the knowledge and experience to properly service an automotive A/C unit. I would recommend you have it professionally serviced. What they will do is evacuate the system, recycling the refrigerant. They will test it for leaks, then put the proper weighed amount of refrigerant in the system. It's difficult giving it a proper charge with nothing but a set of gauges. Back in the days of sight gauges, I used to service my own systems. Not today!

If you insist on trying to do it yourself, get a can of refrigerant with a gauge at the parts store, then slowly add refrigerant till it JUST stops cycling like that - the low side pressure should hold around 30 psi for a while and the temperature of the air coming out the vents should be fairly constant in the 40 degree range. If in doubt what you are doing and why, leave it to a pro.

You also won't get proper readings if you do this when the ambient air temperature is low.

 

Thanks for the reply No offense taken that's why I asked before just refilling it. I won't be able to get an appointment for a week so I just recharged it for now. I want to see if it leaks out fast. Depending on what's wrong and how much it cost to fix May just trade in the truck for a 2013 or 2014 model.

 

a/c can be expensive to fix depending on the failure, but remember it would be cheaper to fix it than a 5 or 6 year loan payment.

 

LoL thanks my wife said the same thing.

 

^ Sometimes they are right!

Find a reputable shop to test the system. They will usually roll test costs into the final repair total. Buy any necessary parts online and save some $$ on any possible parts needed.