AC not working

[tilliepeople]

OK so its a Navigator not an Expedition
My AC is not working. I can see the clutch kicking in and out every couple of seconds
I am assuming that the compressor is seized but I thought I better double check before spending any money

 

[Hamfisted]

Do you have a AC pressure manifold set ? What are the high / low pressures ? I'm guessing the system is just low on freon. You can pick up a can with a hose and gauge on it at Walmart or Home Depot or any auto parts store and attach it to the low side and see if the needle is in the green band when the compressor kicks on. Squeeze the trigger on the gauge/hose adapter to refill the system. They just leak down over a period of time ( years...) and usually need to be topped off.


AC Pro R134 Recharge Kit at Walmart






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[tilliepeople]

If it were just Freon wouldn't the compressor run all the time (with AC on)instead of constanly turning on and off

 

[Hamfisted]

No. There is a low pressure switch (located on the front expansion valve...) that breaks the circuit to the compressor clutch when low side pressure is pulled down below 22 psi by the compressor. Put some freon in it and see how it does.

 

[tilliepeople]

Thank you very much
I'll get a can of freon as soon as i get paid
I have never seen the clutch do that before.

 

[tilliepeople]

Well that didn't work.
I'm going to try the relay next but im not hopefull.
No I do not have a set of gauges but when i hooked up the charge hose it only showed 22lbs and when I started the ac it dropped to 18. Put in about 10 0z and it jumped to 90 while charging and back down to 25 when not.
Backed it off until it never went over 70 but still turning on/off every few seconds

 

[Hamfisted]

Probably still a little low on freon. A full set of gauges would really help.

 

[Copper93]

The A/C clutch is designed to cut in and out depending on pressure. Are you getting any airflow from the vents, defrost or floor? Is the air hot as if the blend door isn’t moving away from the heater core? Also, when the A/C is running does the cooling fan engage to pull air over the condenser and radiator?

 

[tilliepeople]

I have suspected the blend door because it is pretty warm blowing out but that would not make the pump kick in and out
I guess I will have to find a cheap set of gauges and maybe a small vacuum bulb and see what I can come up with
I have changed blend doors before and some vehicles are fairly easy and some are a pain in the butt

 

[tilliepeople]

Update
I put the rest of my can of refrigerant in then flipped the can over to make sure I had all the liquid stuff they put in these cans and left it run for awhile and low and behold I got cold air
At this point I am assuming it needed the lubricant they put in these cans
Just hope it stays working now

 

[GlennSullivan]

It is always a good day when the simple, least expensive solution solves the problem, even if it is temporary. Keep an eye on the pressures, it prolly has a slow leak.

 

[JamaicaJoe]

I have a 2001 Expy. The AC only gets down to about ~50 to 60 F at the dash. It is 83 F ambient and humid.

Yesterday I bought an ACPRO ACP100V which has a gauge with color coded ranges. I connected it per instructions and the Low side pressure was over 55 or 60 PSI and in the red. (ambient 83F) There are no instructions with the kit to reference the pressure to the ambient temperature leading one to think it is either overcharged or needs service. I belieive the AC clutch was engaged throughout the test. Not sure how to proceed.

 

[Hamfisted]

Joe that's overserviced, a little too much freon in the system. You really need a full gauge set on the system to get it just right. You want the low side 35-40 and at least in the green band on those DIY gauges. The high side pressure switch will kick the compressor off when it's overfilled like that.








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[JamaicaJoe]

Today it is about 82F According to the chart and info below I should see, with the system off, a static pressure of 90.2 PSI. If less that would indicate a low charge, if higher would indicate an over charge. Is this correct?
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UPDATE: I found the static pressure was 105 PSI, however the ambient temp (inside the car) much higher due to the car being in the sun for hours. I did open doors and run the fan a while which lowered it.

Withe the AC compressor running for about 5 minutes at 3/4 fan I got a low side reading of about 35 PSI which is 5 or 10 PSI lower than what it should start to be with the 82 F air temperature. My impression is that the refrigerant is slightly low. But it is cooling and the compressor does not appear to be cycling.

It is tricky testing this because getting the correct temperature readings is elusive to me.
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What Your Car's AC Static Pressure Tells You

Learn what static pressure tells you about the condition of your car's AC system. Use it to diagnose a compressor clutch issue.

ricksfreeautorepairadvice.com

 

[Hamfisted]

With a set of gauges. What's your low side, and high side pressures with the AC in the recirculate mode, windows closed, blower(s) on high and the compressor engaged. Not interested in static pressure, other than to say yes, there is some freon in the system before I engage the compressor, to avoid damage.
If you don't have any, you can pick up a set of gauges at Harbor Freight pretty reasonable.




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[GaryH]

@ OP. Yeah, it was just very low on refrigerant. I usually fill until the compressor stops short cycling like that. But without a gauge, you are still just guessing. You can buy a can of R134a that comes with a low pressure side gauge. That helps a lot to see where you are at and keep from over filling, which is bad.