2007 Ford AC low side cycling

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2007 Ford AC low side cycling

Postby kafoo » Mon Aug 31, 2020 5:58 pm

2007 Crown vic 96k miles manual climate control.
The past few weeks I've noticed the AC in my crown vic getting warmer. Performance is ok at idle, 55-60F, compressor rarely cycling. However while driving the compressor short cycles and the air gets warm. Do the great minds here think this is symptomatic of a clog? Or is it just a bad switch and I'm overthinking?
The pressures were a little low so I added a couple OZ of refrigerant to get it to 45 and 215psi with the engine idling, 80F ambient. Then I logged some data.
As soon as rpm comes off idle, the ACCLT(low side cycling switch) opens and cuts the compressor off. Then for 10 seconds the discharge pressure decreases and the air at the vents gets warm while the compressor remains disengaged. The yellow WAC line displays when the clutch is engaged.
It then continues to short cycle via the ACCLT while cruising down the road at low RPM with TC lockup.
I've also noticed I can feel a frequent hesitation from the engine while the compressor engages erratically under acceleration.
Tried tapping and wiggling and pulling on the switch and its wires with the compressor engaged. No luck.
This is the compressor cycling at 2k rpm before I added refrigerant.
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Re: 2007 Ford AC low side cycling

Postby Al9 » Tue Sep 01, 2020 2:52 am

Adding refrigerant until you see correct pressures is a bad approach. It only starves the compressor of lubricant and nothing else.

Reclaim any refrigerant, leak test, vacuum and then charge by weight to the correct specs is what's supposed to be done.
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Re: 2007 Ford AC low side cycling

Postby kafoo » Tue Sep 01, 2020 9:54 pm

I understanding throwing refrigerant into it isn't the best approach. I'm just confused by the behavior of the system.
Symptom of under/overcharging? Water in the system? Faulty Switch? Restriction?
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Re: 2007 Ford AC low side cycling

Postby bohica2xo » Thu Sep 03, 2020 3:57 pm

If that FS18 drags the 4.6 down when cycling you are pushing your luck.

Grab the clutch plate on the compressor & turn it by hand. If it is gritty or notchy you have some parts to replace.

Running it with 60f vents at idle means it is really low on charge. Driving it like that keeps it from returning oil to the compressor.


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