AIR CONDITIONING

[jmt75143]

I was wondering how often the ac clutch is supposed to cycle.

 

[sle2115]

Once you engage the AC, it really shouldn't cycle. Once the AC is turned on, it should engage and pretty much stay that way until you turn the AC off. Now I know there are climate control systems and such that will cycle the compressor as needed, etc. but since you are posting in the 6.9/7.3, it's highly unlikely you have that.

So, I'm guessing it's cycling in and out and...

1. Charge is low/hi and needs adjusted (I'd bet on low unless someone just charged it)
2. Potential issue with overpressurizing from not enough condensor air flow high head pressure.
3. Clutch is failing or power to the clutch has an issue, pressure sensor failure

Use the KISS system and start with basics, get a set of gauges on it and check charge pressure and go from there.

 

[jmt75143]

How do I check the high pressure air flow, and where is the pressure sensor located ?

 

[OLDBULL8]

The question is a little confusing. The pressure switch (sensor) is located on the pass side on that (can) about 3" dia. by 7" tall with a couple of wires coming out of it. In order to check pressures, you have to have a set of gauges. With the A/C running the low pressure should be around 35-45 psi and hi pressure around 140-180. There are ports to hook the gauges too, the large line is the low side.

 

[funnyman06]

Mine cycles, it runs for like 3 minutes and then stops for a couple min then starts back up again. That seemed normal to me, maybe im wrong? Mine also freezes the whole glove box out.

 

[jmt75143]

Thanks for info. The reason I was asking was because the air conditioner clutch cycles every 5 sec's. I was told to check the pressure and if it was good, then it might be the pressure sensor (switch).

 

[DragRag]

It is not the pressure switch, sounds like you are low on charge. Get a nice set of gauges, no cheapies, and put them one. You will see that the pressure drops while the compressor is running, the pressure switch opens, and then the clutch opens. Pressure will rise, switch will close, and then it will start again. When the switch goes bad it usually is stuck open or closed. Switching on and off every 5 seconds is a indicator your swith is working just fine, and reacting to the low charge condition. You can go ahead and top the charge, but if you have a sizable leak, you will find yourself charging again soon. At that point you will need to do a leak check, and repair it. Signs of oil on any of the a/c equipment is a leak indicator, but I like to use an electronic leak detector tp pinpoint myself. LEak detectors of good quality are kind of expensive so I recommend you borrow one of those vs buying.

 

[rempfer]

I hope it's not a problem to hijack this thread. I've been trying to get my 1988 F-250 7.3 IDI's air conditioning working again. Last year, the shop I used flushed (as best as possible) the condensor and evaporator radiators and replaced the compresssor, orifice tube, accumulator. The hoses seemed to be in good shape. After this, last year over the summer, I got about eight hours' worth of use out of the system. The A/C was working the last time I used it last year. Earlier this summer (nine months later) when I went to use the A/C I got only ambient air, and the clutch on the compressor could be observed endlessly cycling briefly on and then off again.

So I took the pickup back the the shop. They recharged the system and replaced the orifice tube which had a bit of crud on it but did NOT appear to be completely obstructed. The air conditioning worked then for the few hours I used it back in July of this year. Yesterday, I took the truck out again and the air conditioner still worked (which was encouraging) but it quit abruptly after I'd driven about five miles.

I raised the hood to see what the compressor was doing and I noticed that the clutch was not engaging at all. So this was different from the brief & frequent cycle behavior that it seemed to do when the refrigerant pressures were off due to the system needing to be recharged.

So the system was working as far as I can tell until the compressor clutch decided to stop engaging. Is there a logical and straightforward way I can proceed with layperson tools only to determine where the problem lies? For example, can I supply battery power to the compressor directly to confirm that the system still refrigerates the air and then work my way back electrically from there? Or would doing that damage the compressor? I can tell you that the blue light on the A/C switch on the dash stayed on and that the heater/cooling circulating fan in the cab continued to blow. The refrigeration process just stopped abruptly apparently when the clutch on the compressor ceased engaging.

I'm no expert, so your detailed suggestions as to how I might proceed would be most welcome.

TIA,

****

 

[79jasper]

You likely have a leak.

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[rempfer]

I have more information on my 1988 F-250 Lariat edition's air conditioning behavior. A few weeks ago had a reputable shop replace an o-ring and low pressure valve due to evidence of leaks. They recharged the system and A/C was working when I left their shop. It works on cool days (kinda when you don't really need it) just fine. But I tried it the just other (80-degree) day and it worked for about a minute and then quit cooling.

Took it back to the shop this cool morning and of course it worked again just fine. He said it "gets down to 41 degrees -- better than modern vehicles." The pressures were just fine and so he suspects a sensor someplace is to blame. I have thought this for quite some time now.

Assuming, if you would play along with me here, that the problem is NOT purely mechanical/coolant level/pressure related what sensor might be the culprit here. And if there's a sensor that could be the problem, would there be a way I could jump a wire across it or otherwise temporarily override it to prove that it's at fault?

So just to recap, all systems seem go with the A/C. It cools steady and well on days when the ambient temperature is low, but will cease cooling (compressor clutch quits engaging) on hot days.

Ideas please?

 

[79jasper]

But you haven't checked the electrical side when the clutch quits engaging?

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[rempfer]

But you haven't checked the electrical side when the clutch quits engaging?

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What, specifically, would you have me do?

 

[79jasper]

When it quits cooling, see if the clutch is engaging. If no, work backwards from the clutch to see where the power quits.
If it is still engaging, what is it doing? Running solid? Cycling in and out? How do the high and low pressures look?

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[no mufflers]

if the compressor is working (sounds like it isn't) it could be a air flow problem on the condenser.

 

[chris142]

The amount of cycling depends on low side pressure. A low system will cycle often. A fully charged system will cycle often on a cool day. A full charged system will rarely cycle on a 100 degree day.