Hey guys need some help with my A/C in '98 F-150 4.6..

My A/C since middle of last week hasn't been cooling very well.. Tonight I had time to look at it a little.. At Idle, the compressor kicks on for maybe a second, then back off for maybe 2-3 seconds, then trys to kick back on, and repeats until switch is turned off.. Also, Last summer, and somewhat earlier this summer, when driving at Highway speeds, 2300 RPM or higher, the A/C never seemed to cool as well as in town at lower rpm..

I was thinking maybe it had too much pressure? but do not have any gauges to check the high side, just low.. Low side reads just about right on, around 70psi @ 100*f with engine off.. With engine running the gauge reads in the Blue, according to my Gauge which is 30-40psi.. Any help is appreciated, as I have a 200+ mile drive tomorrow..

 

Update.. Pressure is much higher then I thought.. About 120psi with engine off, but still in the blue with engine running..

I was going by memory from yesterday and that always screws me..

 

It sounds like the cycling switch may be bad. About 20.00 at the dealer. It is located on the accumulator.

 

Thanks for the info.. Is this something that can be replaced with out evacuting freon from the system?

 

Sigh..

Compressor short-cycling means the system has a leak and is now low on refrigerant. There is nothing faulty about the switch.

"High" pressure with the engine off is normal.

 

mine did that and replaced the fan clutch and added freon. then it kept doing it and cost me 1500 to replace the compressor and bunch of other ****. good luck and take care of it fast. look for freon leaks

 

You are correct in that it was low on refridgerant.. I had 1 14oz can, so I added, figuring if it was too high I couldn't hurt it, since it wasn't kicking on anyway.. Added that and it still cycled, but took much longer before cycled off. Then the 2-3 sec off, and back on for 30 seconds or so, repeat..

I ran to wally world, and picked up some R134A.. Added a can, and the compressor kicked on and stayed on.. But when I revved the engine it kicked off so I added a 2nd can, after revving it did no kick off, and pressure was 35psi at idle.. I took it for a drive, and it stayed cold the whole drive. I realize there is most likely a leak somewhere, I am going to guess the compressor, since it is 12+ years old..

System as been opened once to my kowledge about 4 years ago to replace the heater core, but it was done by one of the best shops in my town, so I know it was done right.. But ever since they did that at highway speeds the A/C never seemed to cool as well as it should, in town all was good.. So, is it possible, with the extreme heat this summer that the low freon caused this problem? Also, keep in mind I did release some freon, due to the 110 psi reading I got, think it was too high. This is why I needed 3 cans instead of 1 or 2, IMO..

 

3 cans would indicate it was damn near empty. You probably have or had a leak some where in the system. During winter months most people will not run their a/c, and in turn will cause the "o" rings in the line connections to dry and shrink a little from lack of oil in the freon keeping the "o" rings lubed and will create a slow leak. Though, if you used your defroster during the winter at all, that would negate that problem since the a/c kicks on with the defroster. Look for some day-glo green some where on all the lines, especially at the connections, and also at the charging ports since sometimes the schrader valves will come a little loose or even go bad. If you did have a leak, you would probably want to have the system emptied into a recovery machine, and then back the system down (vacuumed) for about 20 to 30 minutes to get all the air and moisture removed from the system to get the maximum charge and there by giving you maximum cooling. Hope this helps.

FWIW, and I'm not too sure about these "newer" systems, rule of thumb for pressure on the low side would be at around 30 to 32 psi at idle with a/c running.

 

Man, $1500 really sucks. Sorry to hear that and I definitely feel your pain

 

YEs it was nearly empty.. But I did release, probably 2 cans worth when I thought it might be over charged.. 1 can had I just added it from the get go, would have probably been fine..

 

Try removing the low pressure sensor plug on the dryer and jumping it with a paperclip if it starts running like normal you more than likely have low refridgerant