03 Crown Vic P71
4.6
Just replaced compressor
Reringed all tube fittings
Put in new high pressire switch
New orifice tube installed

Compressor will cycle a few times... cut out al low pressure... then back on at high pressure a few times... then it stops cycling and the p4essure jumps up into the 680psi area...

!!!


Blockage in the condenser or evaporator core?

 

If the compressor failed and stuff circulated throughout the system there is a pretty good chance it plugged the condenser.
After you flush the system , replace the condenser and another new orifice tube and the receiver/dryer, consider putting an inline filter in the line and you should be good to go.
Guys have "gotten away" with shortcuts to those procedures, but from what I can see with your 7.3 project you will do it right !

 

Thanks Hanky.
I figured that was going to be my lott.
I think i will go ahead and replace both the condenser and evap core.
I figure if i just replace everything, it will be that much longer before it has to be opened back up.

Will update with results.

 

A flushing kit is not that expensive, and it will clean all the lines. The filter is an extra insurance policy and should catch anything the flush leaves behind.

 

Ok..
Finally got off my kiester and did the replacements.
The system now has New:

Compressor
Drier/accumulator
Condenser core
Evap core
Orifice tube
Low pressure switch

Im thinking there is not much left but the high pressure switch, or some electrical gremlin.

After the new parts were put in, i pulled a vacuum on the system for a solid 2 hours.
Started engine, set ac to max, and recharged. It never would kick on until, with a full charge on it... i shut the engine off for a couple minutes... then fired it back up. The a/c kicked on and cycled on/off this time... so i charged it until it stayed running... high pressure side was floaring around 180# by the reading on the manifold.

It ran without a hiccup for a good 30 minutes...
The cab was like a deep freezer!

I thought "Awesome! Fixed!" And thought to simulate "driving" by giving it a little more revs...

Within 10 seconds of that... compressor cycled off again...

High pressure side on the manifold reads a hair over 100#
The low pressure side pegs the little gauge on the fill-it-up can...

Im gonna be a balder man by the time i get this sucker... blowin.

Any pointers in any kind of direction?

 

Keep in mind the compressor is supposed to cycle on and off. When the system has the proper amount of refrigerant the low side at around 1000 rpm should get drawn down to around 30 lbs pressure and the low cut off switch opens the power to the compressor clutch, when the system pressure rises to around 45 psi on the low side the low press sw closes and the compressor runs again. A lot depends on the ambient temp, but your hi side press rdg seems a little low and that could be caused by insufficient refrigerant in the system.