My fully charged A/C cycles on and off about every to to 15 seconds. Any ideas why its doing this? It's a 1998 F-250 4.6L with 4WD. thanks.

 

We could always say it may be a little low on refrigerant, but the better thing to do would be to have someone place the gauges on it and that should remove any doubt if that is all that is causing the rapid cycling.

 

if it stays cold don't mess with it

 

That's just it. It does NOT get cold.... pressure is around 40psi and the clutch is engaging then disengaging after only about 3 seconds... it waits about 10 to 15 seconds and then engages again. The clutch does not stay engaged.

 

take it to a a/c repair shop for a correct diagnosis. does it stay running when you have it on 'defroster' and the temp all the way in the blue? if it does, you may have a control selector issue, just a thouhgt. I don't know what correct pressure's are for a/c units these day's. I know they will turn off if too high, too low, and too much difference between the high and the low side.

 

Do you know how to add some R134A to the system?

 

Are you positive that you have a full charge? A full charge for your vehicle would be 42 oz. R-134a.

You could actually have a low charge, bad LOW pressure switch, bad HIGH pressure switch, plugged orifice causing high pressures, clogged condensor causing high pressure or other issues.

You need to put a set of gauges on the LOW and HIGH pressure ports. Then take a pressure reading with the system running. What are the readings along with the ambient air temperature? The ambient air temperature will affect what your actual running pressures.