AC shuts off and on while driving

My AC has always worked well until recently. It blows cold air still but I can feel the system shutting off every 10-15 seconds when driving, even highway driving. I don't smell any chemicals and the AC still blows cold. It's the shutting off and on that worries me. Could it be a sign of low refrigerant/ R-134a? Or the compressor going bad? I don't want to run the AC because if the system is low on refrigerant I don't want to ruin any parts to the compressor. I've ruined compressors on other vehicles before by adding the R-134a in a can so I kinda don't want to do that with this truck, but there are vehicles that have worked better when I've added the R-134a in a can.

 

its low on Freon and the low pressure switch is turning it off, just buy a can of Freon and top it off. turn the fan on high with both windows down and turn a/c on full then top off the Freon level based on the gage reading. to find the leak, usually a leaking o-ring, look for oily residue around fittings to find the leak but if its a slow leak (one can a year) it can be very hard to find so most times I tell people wait until they need more then one can a year to try and find and fix leaks.

often it blows coldest just before it stops blowing altogether because the lower the pressure the lower the temps are going to be until it reaches the point it no longer has enough Freon to cool

 

If you fill it yourself, be sure to use a good set of gauges instead of the one on the can. I accidently overfilled mine because the can gauge was so far off. In that case, I had the exact same symptoms due to overpressure.

Long story short, I drove back to CO from MT in the middle of the night to avoid the heat!

 

The A/C compressor is supposed to cycle on and off. Their is a inline pressure switch the dictates what pressures to cycle on and off. Perfectly normal.

 

Put an A/C gauge set on to check it before adding any more R134. Too much R134 can cause problems. It's not like the old R12 where you could just add a can.

 

I get that cycling off and on is normal but the way mine is acting is not normal. It cycles off and on too quickly. My worry is adding too much freon that it causes the same negative effect. Isn't there supposed to be freon added to the low side and something else done to the High side? I'm not sure of the correct procedure but I remember being told this after I added a can to a vehicle I had a couple years back

 

if you don't know what you are doing go to a place and have it done for you, money well spent for the peace of mind knowing its done right and often they will show you what they are doing and explain it so next time you feel better about doing it yourself.

just don't go to the dealership to have it done.

you only add Freon to the large low pressure line and never connect to the small high pressure lines

this is how it is done:

https://www.youtube.com/watch?v=Bdtwbn7F2QA