# A.C.problem

2011 3.0 140,000 mi.
My daughter following a salt truck got splattered real good with salt. That’s when A.C. started acting up. By her description it sounds like the compressor is trying to seize only when A.C. is activated and then only occasionally. I put gages on it. For me the clutch engages and stays engaged. It didn’t seize for me so it seizes sporadically. At idle the low side pegs out at 350 and high side is 225 steady. Is this a fully restricted expansion valve or a bad compressor or something else?

The expansion valve is what controls the high/low side pressures.

Tester

So if it’s restricted would it cause the low side to be too high?

If it’s wide open, it’ll cause the low side to be high.

Tester

I think I understand. If it’s wide open it allows the high pressure into the low side. But why would the high side be lower than the low side?

I think you are reading the gauge wrong, the low side should never be that high.

I was going to disagree with you, but I went out to look at the gage and you’re right. I didn’t think it could do that either. The gage goes from 120 to 350. It must be closer to 130?

I would assume though that being pegged it matches the high side. These are also the readings with engine off.

Are both of the knobs on your gauge set closed?

Yes, they are both closed.

This time when I started it I experienced more of a rumbling from compressor. It didn’t appear to be seizing.

Those are the readings with the engine off and with the compressor running?

Yes it is.

That can’t be. A normally functioning system can’t have 220lbs of static pressure when it’s off. Someone would have had to somehow grossly overfill the system and it wouldn’t have functioned.

You’re sure the manifold gauges are closed and you’re sure the service valves attached to the ports on the car are in the open position?

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Why not? It’s not normally functioning. If the expansion valve isn’t restricting, then the pump would compress the whole system to equal pressure. That pressure will never lower. Just asking.

For the same reason you can’t be driving down the road and have a tire go from 35psi to 70psi. Where would the air come from? Someone would have to add it, right?

Nope. You’d never get to 220psi with an open expansion valve. It’s a sealed system. Just imagine an electric sump pump with the inlet and outlet hoses connected to each other. The compressor does nothing but pump refrigerant through a closed loop system. If the expansion valve is stuck closed, the low side will be low or go into a vacuum because the compressor is sucking from a closed off hose. If the expansion valve is stuck open, the high side will be lower than expected and the low side will be higher, since there is no restriction in the loop for the compressor to push against and the low side will be constantly sucking in what the high side is pushing out.

All that aside, you can’t have 200psi in a static system. A fully charged system would be around 100psi on a warm day, less as the temp drops. You’re over 200 in freezing weather. Where did the extra refrigerant come from?

Ok. I’ll hook the gages to another vehicle to check the gage later today.

It appears that the pressures are equalized at around 215 PSI. A lot of people here–including the OP–are making the assumption that the “retard” range on the low-side gauge is to-scale when in fact on cheap gauges that is often not the case.

What I mean by this is once the low side is above 120 PSI, but below 350 PSI (which is the maximum pressure the gauge can withstand without being permanently damaged), you have no idea what the actual pressure is. If the needle is halfway between 120 and 350 PSI, this does not imply that the actual pressure is halfway between these two values.

Static pressure on both sides with engine/AC off should be in the 120 PSI range; give or take a tiny bit either way but 130 might be permissible although that seems a bit much based on prior experience.

What are the pressures at idle with the compressor engaged and what about cooling fan operation?

Maybe the compressor is not seizing and what you hear is simply the clutch kicking in and out because of a pressure issue; or possibly an excessive air gap in the clutch. I can’t speak for the Escape but with several Fords I’ve owned I discovered the low side pressure switch is adjustable with a jeweler’s screwdriver. At this point I would not jump that far ahead just yet.
Some Nissans even had adjustable expansion valves.

The pressures read the same in every condition. Engine off,engine on, clutch engaged clutch disengaged. Clutch is constantly on when commanded. It is off when commanded to be off. The coolant fans are operational.